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🐾 VOMITING & DIARRHEA IN VETERINARY MEDICINE

A Complete Conceptual Guide for Veterinary Students & Practitioners

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PART 1: VOMITING (EMESIS)

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1.1 DEFINITION

• Vomiting - active process, preceded by nausea and retching
• Regurgitation - passive process, no abdominal effort, no nausea (covered in differentiation section)

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1.2 ANATOMY OF THE VOMITING REFLEX - PATHOPHYSIOLOGY

The "Vomiting Center" (Emetic Center)

The Chemoreceptor Trigger Zone (CTZ)

• It lies OUTSIDE the blood-brain barrier (BBB) - so blood-borne toxins, drugs, and metabolic waste products can reach it directly
• Dogs have a very sensitive CTZ (dogs vomit easily; cats are more resistant)
• Key receptors: D2 (dopamine), 5-HT3 (serotonin), NK1 (neurokinin/substance P), alpha-2 adrenergic, opioid receptors

Step-by-Step Mechanism of the Vomiting Act

1. Antiperistalsis begins - Retrograde peristalsis starting as far down as the ileum pushes contents back to stomach/duodenum in 3-5 minutes
2. Distension of duodenum triggers the actual vomiting act
3. Deep breath is taken
4. Hyoid bone and larynx rise - opens upper esophageal sphincter
5. Glottis closes - prevents aspiration of vomitus into lungs
6. Soft palate rises - closes posterior nares (prevents nasal expulsion)
7. Diaphragm contracts downward simultaneously with abdominal wall muscles - squeezes stomach like a vice
8. Lower esophageal sphincter (cardia) relaxes completely
9. Gastric contents expelled through esophagus and out

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1.3 CLASSIFICATION OF VOMITING

By Duration

By Timing/Character (Clinically Important!)

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1.4 CAUSES OF VOMITING IN DOGS AND CATS

PRIMARY (GI) CAUSES

• Dietary indiscretion (garbage eating, coprophagia) - most common cause in dogs
• Rapid eating / overeating
• Sudden diet change
• Food intolerance / food allergy

• Canine Parvovirus (CPV-2) - most serious viral cause in young dogs; hemorrhagic vomiting + diarrhea
• Canine Distemper Virus
• Feline Panleukopenia (feline parvovirus) - cats
• Canine Coronavirus
• Rotavirus
• Salmonella, Campylobacter, Clostridium perfringens (bacterial)
• Helicobacter pylori (gastric spiral bacteria)
• Giardia, Cryptosporidium, Toxocara (roundworms), Hookworms

• Foreign body (linear or non-linear)
• Gastric Dilatation-Volvulus (GDV) - emergency in large breed dogs
• Intussusception (telescoping of intestine into itself)
• Pyloric stenosis / hypertrophic pyloric gastropathy
• Intestinal obstruction
• Mesenteric volvulus

• Gastritis (acute or chronic)
• Gastric ulceration (NSAID-induced, mast cell tumor, Helicobacter)
• Inflammatory Bowel Disease (IBD)
• Pancreatitis (very common in dogs, particularly Miniature Schnauzers)
• Cholangiohepatitis (cats)
• Peritonitis

SECONDARY (EXTRA-GI / SYSTEMIC) CAUSES

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1.5 CLINICAL SIGNS / HISTORY TO COLLECT

• Nausea: drooling (hypersalivation), lip-licking, repeated swallowing, restlessness, grass eating
• Retching: rhythmic abdominal contractions before expulsion

1. When did it start? (acute vs. chronic)
2. How often? (frequency)
3. What does the vomit look like? (content, color, blood?)
4. Relation to feeding?
5. Access to garbage, toxins, foreign objects?
6. Other signs? (diarrhea, weight loss, PU/PD [polyuria/polydipsia], lethargy)
7. Vaccination status?
8. Current medications?
9. Deworming history?
10. Travel history / exposure to other animals?

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1.6 PHYSICAL EXAMINATION

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1.7 DIAGNOSTICS FOR VOMITING

Minimum Database

• CBC (Complete Blood Count): Leukocytosis (infection/inflammation), neutropenia (parvovirus!), anemia (GI blood loss), thrombocytopenia
• Biochemistry panel: BUN/creatinine (renal), ALT/ALP (hepatic), glucose (DKA), calcium, electrolytes
• Urinalysis: Isosthenuria (renal), glucosuria (DKA), proteinuria
• Fecal exam: Parasites, parvovirus antigen test
• Electrolytes: Hyponatremia + hyperkalemia = classic Addison's pattern; Na:K ratio < 27:1 is suspicious

Advanced Diagnostics

• Abdominal radiographs (X-rays): Foreign body, gas patterns, obstruction, GDV ("double-bubble" sign), intussusception
• Abdominal ultrasound: Mass lesions, pancreatic changes, intussusception (target sign), wall thickening, lymphadenopathy, free fluid
• Gastroscopy/endoscopy: Direct visualization, biopsy
• SNAP Parvo test: Rapid fecal antigen test for CPV
• Serum cPLI (canine Pancreatic Lipase Immunoreactivity): For pancreatitis
• ACTH stimulation test: For hypoadrenocorticism
• Serum T4: Hyperthyroidism (cats > 8 years)
• Bile acids (pre- and post-prandial): Portosystemic shunt, hepatic dysfunction
• Serum B12 (cobalamin) / folate: Chronic GI malabsorption

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1.8 TREATMENT OF VOMITING

Immediate Stabilization

1. IV fluid therapy - correct dehydration, electrolyte imbalances, acid-base disturbances
   • Use Lactated Ringer's (LR) or Normal Saline based on electrolyte status
   • Hypokalemia: add KCl supplementation to fluids
   • Metabolic alkalosis (from pyloric obstruction): correct with NS + KCl

Antiemetics (Anti-vomiting drugs)

Gastroprotectants

• Omeprazole (PPI): Best gastric acid suppression; prevents ulcers
• Famotidine (H2 blocker): Less potent than PPI
• Sucralfate: Coats ulcers; excellent for gastric/esophageal ulcers (give separately from other meds - binds them!)

Dietary Management

• NPO (Nil Per Os - nothing by mouth): Short fasts (2-4 hours) then bland diet (boiled chicken + rice)
• Early enteral nutrition is now preferred over prolonged fasting - supports gut mucosal integrity
• Avoid in obstruction (must be ruled out first!)

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PART 2: DIARRHEA

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2.1 DEFINITION

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2.2 PATHOPHYSIOLOGY - THE 4 MECHANISMS OF DIARRHEA

Mechanism 1: OSMOTIC DIARRHEA

• Mechanism: Non-absorbed osmotically active substances remain in the intestinal lumen, drawing water in by osmosis
• Causes: Lactose intolerance, maldigestion (exocrine pancreatic insufficiency - EPI), malabsorption, overfeeding of fermentable carbohydrates, lactulose
• Key feature: Stops when animal fasts (stops eating) - "fast-responsive diarrhea"
• Fecal osmolar gap: HIGH (measured osmolarity much higher than calculated)

Mechanism 2: SECRETORY DIARRHEA

• Mechanism: Active secretion of water and electrolytes INTO the lumen by enterocytes, driven by bacterial toxins, bile acids, fatty acids, or inflammatory mediators (e.g., prostaglandins, VIP)
• Causes: Cholera toxin (activates adenylyl cyclase -> cAMP -> Cl- secretion), E. coli enterotoxin, Clostridium perfringens, bile acid malabsorption, VIPoma (rare)
• Key feature: Does NOT stop with fasting (secretion continues even on empty gut)
• Produces large volumes of watery diarrhea

Mechanism 3: INCREASED MUCOSAL PERMEABILITY (Exudative / Protein-losing)

• Mechanism: Damage to the intestinal epithelium allows leakage of plasma proteins, blood, and inflammatory cells into the lumen
• Causes: Parvovirus, IBD, intestinal lymphoma, ulceration, intussusception, severe parasitism, Protein-Losing Enteropathy (PLE)
• Key feature: Hypoproteinemia (low albumin + low globulins - pan-hypoproteinemia), possible edema, ascites
• Diarrhea is often bloody or contains mucus

Mechanism 4: ABNORMAL MOTILITY

• Mechanism: Either too fast (hypermotility) - reduced contact time, inadequate absorption; or too slow (hypomotility/ileus) - bacterial overgrowth, fermentation, gas
• Causes (hypermotility): Psychogenic stress, hyperthyroidism (cats), irritable bowel syndrome (IBS)
• Causes (hypomotility): Post-operative ileus, peritonitis, hypokalemia, opioid use

Note from Today's Veterinary Practice: In most small animal diseases, MULTIPLE mechanisms contribute simultaneously, and osmotic forces plus mucosal permeability changes are the most common in dogs and cats.

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2.3 SMALL BOWEL vs. LARGE BOWEL DIARRHEA - CRITICAL DIFFERENTIATION

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2.4 CAUSES OF DIARRHEA IN DOGS AND CATS

DIETARY

• Dietary indiscretion (most common acute cause)
• Sudden diet change
• Food intolerance / allergy (beef, dairy, wheat most common)
• Garbage intoxication (enterotoxins from spoiled food)
• Overfeeding

INFECTIOUS

• Canine Parvovirus (CPV-2): Hemorrhagic diarrhea, vomiting, severe leukopenia (neutropenia!), panleukopenia in puppies; targets rapidly dividing crypt cells of intestine
• Feline Panleukopenia Virus (FPV): Cats; same parvovirus family; similar clinical signs
• Canine Coronavirus (CCV): Milder than parvovirus; often concurrent
• Rotavirus: Young animals mainly

• Salmonella spp.: Zoonotic! Bloody diarrhea, fever, septicemia risk
• Campylobacter jejuni: Common in puppies/kittens from shelters; watery to bloody diarrhea; zoonotic!
• Clostridium perfringens: Produces CPE and NetF toxins; associated with AHDS in dogs
• Clostridium difficile: Similar to humans; especially after antibiotic use
• E. coli (pathogenic strains)
• Yersinia enterocolitica

• Giardia: Pale, greasy, soft stools; small bowel; very common in young animals and shelters; zoonotic!
• Cryptosporidium: Watery diarrhea; immunocompromised risk; zoonotic!
• Toxocara canis/cati (Roundworms): Young animals; pot-bellied appearance
• Ancylostoma (Hookworms): Blood-sucking; anemia + bloody diarrhea; zoonotic!
• Trichuris vulpis (Whipworms): Large bowel diarrhea + hematochezia in dogs; typically not in cats
• Tritrichomonas foetus: Cats (especially Bengals); large bowel diarrhea; resistant to many drugs

• Histoplasma capsulatum (endemic regions)
• Pythium insidiosum (pythiosis - subtropical regions)

INFLAMMATORY / IMMUNE-MEDIATED

• Inflammatory Bowel Disease (IBD): Lymphoplasmacytic, eosinophilic, or granulomatous infiltration; chronic, often concurrent vomiting; requires biopsy for diagnosis
• Protein-Losing Enteropathy (PLE): End-result of severe intestinal disease (IBD, lymphoma, lymphangiectasia); marked hypoproteinemia, edema, ascites
• Lymphocytic-Plasmacytic Enteritis: Most common form of IBD
• Eosinophilic Gastroenteritis: Often food-triggered; eosinophilia may be present

STRUCTURAL / MECHANICAL

• Intussusception (telescoping of bowel - classic in puppies after parvovirus infection!)
• Foreign body (linear: string in cats is CLASSIC; causes plication of intestines)
• Intestinal volvulus
• Rectal polyps (large bowel)

MALABSORPTIVE / MALDIGESTIVE

• Exocrine Pancreatic Insufficiency (EPI): Insufficient digestive enzymes; classic signs = profuse, yellowish, greasy, voluminous diarrhea, weight loss despite ravenous appetite; common in German Shepherds
• Small Intestinal Bacterial Overgrowth (SIBO): Now termed Antibiotic-Responsive Diarrhea (ARD); deconjugated bile acids cause osmotic + secretory diarrhea; responds to tylosin or metronidazole
• Intestinal lymphangiectasia (protein-losing; dilated lymphatics; chylous ascites)

SYSTEMIC / METABOLIC

• Hypoadrenocorticism (Addison's): Chronic intermittent diarrhea + vomiting; Na:K ratio < 27:1; "great imitator"
• Renal failure (uremic enteritis)
• Liver failure (bile acid dysregulation)
• Hyperthyroidism (cats) - hypermotility
• DKA (osmotic diarrhea from glycosuria)

NEOPLASTIC

• Intestinal lymphoma (most common GI tumor in cats!)
• Adenocarcinoma
• Mast cell tumor (histamine causes gastric hypersecretion and diarrhea)
• Leiomyosarcoma, GIST

SPECIAL ENTITY: Acute Hemorrhagic Diarrhea Syndrome (AHDS)

• Sudden onset of severe hemorrhagic diarrhea (often "raspberry jam" consistency)
• Marked hemoconcentration: PCV (packed cell volume) can reach 60-75%+ while total protein remains NORMAL (plasma protein stays in vessels but fluid leaks out)
• Associated with netF-positive Clostridium perfringens type A
• Predilection for small/toy breeds (Miniature Poodle, Miniature Schnauzer, Yorkshire Terrier)
• Treatment: IV fluids (primary), antibiotics (ampicillin or metronidazole); antiemetics; most recover within 24-48 hours
• Key differentiator: PCV very high but TP normal (vs. hemorrhage where both drop!)

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2.5 CLINICAL SIGNS AND HISTORY

• Character of stool: watery, soft, mucoid, bloody?
• Small bowel vs. large bowel signs (use the table above)
• Tenesmus vs. polyuria/polydipsia
• Weight loss (suggests chronic / malabsorptive disease)
• Appetite: increased with EPI (ravenous but losing weight); decreased with IBD/neoplasia
• Other animals or humans affected? (suggests zoonotic cause - Salmonella, Campylobacter, Giardia)
• Deworming / vaccination history

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2.6 METABOLIC CONSEQUENCES OF DIARRHEA

Metabolic acidosis develops from: (1) loss of bicarbonate-rich intestinal secretions, (2) hypovolemia causing anaerobic metabolism and lactic acidosis. - (Ngwenyama, Vet Clin North Am Small Anim Pract, 2026)

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2.7 DIAGNOSTICS FOR DIARRHEA

Minimum Database

• CBC: Leukocytosis (bacterial/inflammatory), neutropenia + lymphopenia (parvovirus!), eosinophilia (parasites, eosinophilic enteritis), anemia (chronic blood loss - hookworms, IBD)
• Biochemistry: Total protein/albumin (low = PLE), glucose, BUN, liver enzymes, electrolytes
• Urinalysis
• Fecal flotation + direct smear: Parasites (ova, larvae, trophozoites)
• Fecal culture: Salmonella, Campylobacter
• SNAP Giardia antigen test
• SNAP Parvo antigen test

Advanced

• Serum TLI (Trypsin-Like Immunoreactivity): Diagnostic test for EPI - low TLI = EPI; high = pancreatitis
• Serum cPLI/fPLI: Pancreatitis
• Serum cobalamin (B12) and folate: B12 low = terminal ileal disease or SIBO; folate high = SIBO; both low = diffuse small bowel disease
• Serum albumin: PLE (< 2.0 g/dL severe)
• Abdominal radiographs + ultrasound
• Endoscopy + biopsy: Definitive for IBD, lymphoma (requires FULL-THICKNESS biopsy for diffuse infiltrative lymphoma)
• PARR (PCR for Antigen Receptor Rearrangements): Differentiates IBD from alimentary lymphoma

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2.8 TREATMENT OF DIARRHEA

Fluid Therapy - Phased Approach (2026, Ngwenyama)

1. Resuscitation: Rapid IV fluid boluses for hypovolemic shock (crystalloids - LRS, NS, or Plasma-Lyte)
2. Optimization: Correct remaining deficits over 12-24 hours; add KCl to fluids for hypokalemia
3. Stabilization: Maintenance rate; monitor electrolytes frequently
4. De-escalation: Transition to oral intake when tolerated

Antidiarrheal / Supportive Medications

Dietary Management

• Bland diet: Easily digestible, low fat, low fiber - boiled chicken/white fish + white rice
• Hydrolyzed protein diet: Food allergy / adverse food reaction
• High-fiber diet: Large bowel diarrhea, fiber-responsive diarrhea (trichuris, idiopathic colitis)
• Highly digestible / EPI diet: Enzyme supplementation (Viokase, pancreatic enzyme powder)
• Withhold food 12-24 hours (acute mild diarrhea only - do NOT fast severely ill animals)

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PART 3: DIFFERENTIATION OF KEY DISEASES

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3.1 VOMITING vs. REGURGITATION vs. RETCHING (Must Know!)

3.2 KEY DISEASE DIFFERENTIATIONS

Parvovirus vs. AHDS (Hemorrhagic Gastroenteritis)

IBD vs. Alimentary Lymphoma (Cats - Very Common Exam Topic)

EPI vs. IBD/PLE (Small Bowel Malabsorption)

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PART 4: PATHOGNOMONIC SIGNS

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PART 5: IMPORTANT EXAM / INTERVIEW / CLIENT QUESTIONS

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Q1. What is the most common cause of acute vomiting and diarrhea in adult dogs?

Q2. What is the most dangerous cause of acute vomiting and diarrhea in puppies?

Q3. How do you differentiate small bowel from large bowel diarrhea?

Q4. What is the Na:K ratio and what does a low ratio mean?

Q5. What antiemetic is the gold standard in small animal veterinary medicine?

Q6. Why should you NOT use metoclopramide in suspected GI obstruction?

Q7. What is the pathognomonic CBC finding in canine parvovirus?

Q8. What is AHDS and how is it different from parvovirus?

Q9. What is the diagnostic test for Exocrine Pancreatic Insufficiency (EPI)?

Q10. What is a linear foreign body and why is it dangerous in cats?

Q11. What is PLE and what are its hallmarks?

Q12. What emetic do you use in dogs vs. cats?

• Dogs: Apomorphine (D2 agonist; given subconjunctivally or IV; fast acting)
• Cats: Xylazine (alpha-2 agonist; IM or SQ; also causes sedation)
• Alternative (both): 3% hydrogen peroxide (dogs only - irritant; not in cats - toxic!)

Q13. When is vomiting induction CONTRAINDICATED?

• Caustic/corrosive ingestion (acids, alkalis) - re-exposure burns esophagus
• Petroleum products
• Already unconscious or seizuring patient
• Respiratory compromise
• Foreign body that could cause more trauma on the way back up
• More than 2-4 hours after ingestion (already absorbed)

Q14. How do you treat GDV (Gastric Dilatation-Volvulus)?

1. Stabilize first - IV fluids, oxygen, pain relief, treat shock
2. Decompress stomach - pass orogastric tube OR trocharize (needle through flank)
3. Surgical correction - detort stomach + gastropexy (to prevent recurrence)
4. Monitor for cardiac arrhythmias (ventricular premature contractions - common post-GDV)

Q15. What are the 4 mechanisms of diarrhea?

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PART 6: QUICK SUMMARY FLOWCHART

VOMITING / DIARRHEA PATIENT
          |
    ┌─────┴─────┐
Is it VOMITING    Is it DIARRHEA
or REGURGITATION? Small vs. Large Bowel?
          |              |
   [History + PE]   [Character of stool]
          |
   Acute (< 7 days) → Dietary? Infectious? Toxin? Obstruction?
   Chronic (> 7 days) → IBD? Neoplasia? EPI? Systemic disease?
          |
   [MINIMUM DATABASE: CBC, CHEM, UA, FECAL]
          |
   ┌──────────────┐
   Parvo test?       Na:K ratio?     Ultrasound?
   PCV/TP?           TLI?            Radiographs?
          |
   [TREATMENT: Fluids, Antiemetics, Antibiotics if indicated,
    Bland diet, Treat underlying cause]

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REFERENCES & SOURCES

• Guyton & Hall Textbook of Medical Physiology (physiology of vomiting/diarrhea, mechanisms)
• Sleisenger & Fordtran's Gastrointestinal and Liver Disease (GI pathophysiology)
• Ngwenyama TT. "Fluid and Electrolyte Therapy in the Patient with Vomiting and Diarrhea." Vet Clin North Am Small Anim Pract. 2026 [PMID: 41162294]
• Mazzaferro EM. "Update on Canine Parvoviral Enteritis." Vet Clin North Am Small Anim Pract. 2025 [PMID: 40044515]
• Dupont N, et al. "Retrospective study of 237 dogs with AHDS." J Vet Intern Med. 2021 [PMID: 33638574]
• Today's Veterinary Practice: "Approach to Diagnosis and Therapy of the Patient with Acute Diarrhea" (2013)
• Washington State University Veterinary Teaching Hospital - Diarrhea in Dogs and Cats

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1. Vomiting ki complete neurology - CTZ, vagal afferents, vomiting center
2. Diarrhea ke 4 mechanisms - osmotic, secretory, permeability, motility
3. Small vs. large bowel diarrhea differentiation (exam mein zaroor aata hai)
4. Key diseases ki differentiation - parvovirus vs. AHDS, IBD vs. lymphoma, EPI vs. PLE
5. Pathognomonic signs jo seedha diagnosis batate hain
6. Treatment protocols - antiemetics, fluid therapy, dietary management
7. Interview/exam questions with complete answers

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🐾 VETERINARY MASTERCLASS GUIDE

REGURGITATION + PANCREATITIS + LIVER DISEASE

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SECTION 1: REGURGITATION

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1.1 DEFINITION

Key concept to remember: Regurgitation is an ESOPHAGEAL problem. Vomiting is a GASTRIC problem. This is the most fundamental distinction in veterinary gastroenterology.

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1.2 VOMITING vs. REGURGITATION - MASTER TABLE

Pathognomonic clue:

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1.3 ANATOMY - WHY REGURGITATION HAPPENS

• Upper Esophageal Sphincter (UES): At pharyngo-esophageal junction; striated muscle; prevents air entry
• Lower Esophageal Sphincter (LES) / Cardia: At gastroesophageal junction; prevents gastric reflux

• Dogs: Entirely STRIATED (voluntary) muscle throughout the whole esophagus
• Cats: Striated in upper 2/3, smooth muscle in lower 1/3

1. Coordinated peristalsis (primary and secondary waves)
2. Intact vagal innervation (CN X)
3. Normal neuromuscular junction (acetylcholine release)
4. Normal smooth/striated muscle function

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1.4 CAUSES OF REGURGITATION

ESOPHAGEAL CAUSES (Primary)

• Megaesophagus = generalized dilation and loss of peristalsis of the entire esophagus
• Food accumulates and cannot move to the stomach - it sits, ferments, and is regurgitated
• Can be congenital (present at birth) or acquired (develops later in life)

• Seen in puppies when weaning begins (~ 3 months of age)
• Pathophysiology: defect in vagal afferent innervation or esophageal muscle abnormality
• Predisposed breeds: Wire Fox Terrier (autosomal recessive), Miniature Schnauzer (autosomal dominant/recessive), Great Dane, German Shepherd, Labrador Retriever, Newfoundland, Irish Setter, Chinese Shar-Pei

• Foreign bodies (bones most common in dogs; sewing needles in cats)
• Esophageal stricture (post-esophagitis scarring; post-vomiting; pill esophagitis from doxycycline in cats!)
• Esophageal neoplasia (squamous cell carcinoma, leiomyoma, GIST)
• Extraluminal compression (lymph nodes, mediastinal masses, lung tumors)

• Developmental anomaly where the aortic arch forms on the RIGHT instead of left
• Creates a fibrous ring that encircles and compresses the esophagus at the heart base
• Classic presentation: puppy/kitten that regurgitates when starting solid food (weaning age)
• Diagnosis: Radiography (dilation of esophagus CRANIAL to heart base)
• Treatment: SURGICAL LIGATION and cutting of the ligamentum arteriosum
• Pathognomonic: Regurgitation in young animal + esophageal dilation cranial to heart on X-ray

• Causes: Gastroesophageal reflux (GERD), anesthesia (acid reflux during GA), vomiting, foreign bodies, doxycycline capsules (cats - pill burns), feeding tubes
• Signs: Regurgitation, hypersalivation, odynophagia (painful swallowing), repeated swallowing
• Can progress to esophageal stricture if chronic

• Stomach acid refluxes into esophagus (especially during anesthesia - animals positioned in Trendelenburg/head-down)
• Causes esophagitis, pain, regurgitation

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1.5 CLINICAL SIGNS

• Regurgitation (hallmark sign) - passive, tubular food
• Dysphagia (difficulty swallowing) - repeated swallowing attempts
• Odynophagia - painful swallowing (esophagitis)
• Hypersalivation / ptyalism (drooling)
• Halitosis (bad breath from fermented food in esophagus)
• Weight loss / failure to thrive (food never reaches stomach)
• Aspiration pneumonia - MOST DANGEROUS COMPLICATION
  • Regurgitated material enters airway
  • Signs: cough, dyspnea, fever, nasal discharge, crackles on auscultation
  • Cranioventral lung lobe consolidation on X-ray
  • Can be FATAL

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1.6 DIAGNOSTICS

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1.7 TREATMENT

Underlying Cause Treatment (MOST IMPORTANT)

• Myasthenia Gravis: Pyridostigmine (AChE inhibitor) - prolongs ACh action at NMJ; ± immunosuppression (prednisolone)
• Hypothyroidism: Levothyroxine (L-thyroxine) supplementation
• Addison's disease: Fludrocortisone (mineralocorticoid) + prednisolone
• PRAA: Surgical ligation of ligamentum arteriosum
• Foreign body: Endoscopic retrieval or surgery
• Esophageal stricture: Balloon dilation (endoscopic)
• Esophagitis: PPIs (omeprazole), sucralfate, feeding management

Supportive Management for Megaesophagus

• "Bailey Chair" feeding: Feed the dog in an UPRIGHT position (45-90 degrees, like a human) so gravity helps food fall into the stomach; dog must remain upright for 15-30 minutes after eating
• Multiple small meals daily - easier to swallow in smaller amounts
• Food texture modification - some dogs do better with liquids (water + kibble slurry), others with solid food (trial and error)
• Elevated food bowl - less beneficial than upright positioning
• Nasogastric (NG) or esophagostomy tube - if severe malnutrition
• Sildenafil (phosphodiesterase-5 inhibitor) - one study showed some improvement in LES relaxation and esophageal function; experimental
• Aspiration pneumonia treatment: Antibiotics (broad-spectrum), oxygen, nebulization

Prognosis

• Congenital megaesophagus: Variable - some puppies improve as the nervous system matures; others have lifelong disease
• Secondary megaesophagus (MG, Addison's, hypothyroid): GOOD if underlying disease is treated early
• Idiopathic megaesophagus: POOR prognosis; aspiration pneumonia is major mortality cause (VCA Animal Hospitals)

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═══════════════════════════════════

SECTION 2: PANCREATITIS

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2.1 DEFINITION

• Acute Pancreatitis = Reversible inflammatory episode; function can return to normal if cause is removed
• Chronic Pancreatitis = Repeated episodes; causes irreversible destruction of exocrine pancreas; leads to fibrosis and loss of acinar cells

"Acute pancreatitis is caused by autodigestion of the pancreas by intraacinara (within acinar cells) activation of pancreatic enzymes." - Robbins & Kumar Basic Pathology

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2.2 NORMAL PANCREATIC PHYSIOLOGY (Review)

1. Exocrine function (acinar cells - 80% of pancreas): Produce digestive enzymes (amylase, lipase, trypsin, chymotrypsin, elastase, phospholipase) as INACTIVE PROENZYMES (zymogens) to prevent self-digestion
2. Endocrine function (islets of Langerhans - 20%): Produce insulin (beta cells), glucagon (alpha cells), somatostatin (delta cells)

The Safety Mechanism That Prevents Autodigestion:

• Enzymes are stored as INACTIVE zymogens in secretory granules
• They are only activated in the DUODENUM by enteropeptidase (enterokinase), which converts trypsinogen → TRYPSIN
• Trypsin then activates ALL other proenzymes
• Intracellular trypsin inhibitors (PSTI/SPINK1) neutralize any accidentally activated trypsin

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2.3 PATHOPHYSIOLOGY OF PANCREATITIS

THREE PATHWAYS OF INITIATION (Robbins & Kumar):

• Gallstone or biliary sludge blocks the common bile duct / ampulla of Vater
• Intraductal pressure rises → enzyme-rich interstitial fluid accumulates
• Lipase (already active) causes local fat necrosis
• Inflammatory cytokines released → edema, impaired blood flow → ischemia → acinar cell injury

• Direct damage to acinar cells by:
  • High-fat diet / dietary indiscretion (most common in dogs)
  • Hypertriglyceridemia (Miniature Schnauzer predisposition!)
  • Ischemia
  • Drugs (azathioprine, bromides, potassium bromide, L-asparaginase, sulfonamides, zinc, tetracyclines)
  • Toxins
  • Trauma
• Injured cells release proenzymes → intracellular activation

• Normally, digestive enzymes and lysosomal hydrolases travel in SEPARATE pathways
• When packaging goes wrong (metabolic injury), they merge → proenzymes activate inside lysosomes → lysosomal rupture → enzyme release

Cascade of Damage Once Trypsin Activates:

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2.4 CAUSES OF PANCREATITIS IN DOGS AND CATS

IN DOGS:

IN CATS: (Different and important!)

"FELINE TRIADITIS" (Unique to Cats!)

The simultaneous presence of:

1. Pancreatitis
2. Inflammatory Bowel Disease (IBD)
3. Cholangitis (liver/bile duct inflammation)

Because in cats, the bile duct and pancreatic duct share a COMMON OPENING into the duodenum (unlike dogs where they open separately). So infection/inflammation can spread between all three organs easily. Armstrong & Williams, Top Companion Anim Med, 2012 [PMID: 23148855]

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2.5 CLINICAL SIGNS

In Dogs (more classic presentation):

• Vomiting - common, often the presenting complaint
• Abdominal pain - dog adopts "prayer position" (front legs down, hindquarters up) to relieve abdominal discomfort - this is nearly PATHOGNOMONIC!
• Anorexia / inappetence
• Lethargy, depression
• Diarrhea (less consistent)
• Fever
• Dehydration
• Cranial abdominal pain on palpation
• Severe cases: jaundice (biliary obstruction), ascites, respiratory distress (ARDS), collapse (shock)

In Cats (MUCH more subtle - that's why it's frequently missed!):

• Anorexia (most common sign - 87%)
• Lethargy
• Dehydration
• Hypothermia (unusual - cats can be COLD, not hot!)
• Vomiting (less common than dogs - only ~50%)
• Abdominal pain (often absent or hard to detect)
• Jaundice (from concurrent cholangitis)
• Weight loss

"Few of the diagnostic tests of value in the dog were helpful in cats." - Armstrong & Williams (2012)

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2.6 DIAGNOSTICS

Blood Tests:

Imaging:

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2.7 TREATMENT

1. Rest the pancreas (NPO initially)
2. Correct fluid and electrolyte deficits
3. Control pain and vomiting
4. Prevent complications

Step-by-Step Treatment Protocol:

• Correct dehydration and hypovolemia
• Lactated Ringer's Solution (LRS) or Plasma-Lyte as first choice
• Add KCl if hypokalemia present
• Avoid overhydration (can worsen pancreatic edema)

• Pancreatitis is VERY PAINFUL
• Buprenorphine (partial opioid agonist) - excellent for moderate pain
• Fentanyl CRI (constant rate infusion) - for severe pain
• Maropitant (Cerenia) - also has visceral analgesic properties; useful concurrently
• Avoid NSAIDs (worsen renal perfusion and GI issues)

• Maropitant (Cerenia) - first-line; NK1 antagonist
• Metoclopramide CRI - prokinetic, helps gastric emptying; also antiemetic
• Ondansetron - for severe/refractory vomiting

• Old teaching: "NPO for 24-48 hours to rest the pancreas"
• New evidence: Early enteral feeding (naso-esophageal or naso-gastric tube) IMPROVES outcomes; reduces bacterial translocation; supports gut integrity; prevents muscle wasting
• Begin small amounts of low-fat, highly digestible diet ASAP
• Cats: MUST be fed early to prevent hepatic lipidosis!
• If can't eat voluntarily: nasogastric tube or esophagostomy tube placement

• NOT routinely recommended (pancreatitis is mostly sterile initially)
• Use only if evidence of infection: fever, positive blood cultures, sepsis, aspiration pneumonia
• If needed: ampicillin/sulbactam, metronidazole, or enrofloxacin

• Gastroprotectants: Omeprazole (PPIs) if vomiting, gastric ulceration risk
• Plasma transfusion: Provides alpha-macroglobulins that neutralize proteases; used in severe cases
• Dopamine: Low-dose to maintain splanchnic blood flow (controversial)
• Surgery: For pancreatic abscess, pseudocyst, necrosis debridement

• DIC: Fresh frozen plasma, heparin (controversial)
• Hypocalcemia: Slow IV calcium gluconate supplementation
• Hyperglycemia/DKA: Insulin therapy
• ARDS: Oxygen therapy, mechanical ventilation
• Hepatic lipidosis (cats): Aggressive enteral nutrition

• Low-fat diet PERMANENTLY
• Omega-3 fatty acid supplementation
• Cobalamin (B12) supplementation if deficient (common with EPI)
• If leads to EPI: Pancreatic enzyme supplementation
• If leads to diabetes mellitus: Insulin therapy
• Cats with chronic pancreatitis: Often benefit from prednisolone (has anti-inflammatory effect in cats)

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2.8 COMPLICATIONS

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2.9 PANCREATITIS EXAM QUESTIONS

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SECTION 3: LIVER DISEASE (HEPATIC DISEASE)

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3.1 OVERVIEW OF LIVER FUNCTION

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3.2 CLINICAL SIGNS OF LIVER DISEASE

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3.3 HEPATIC ENCEPHALOPATHY (HE) - Key Topic

• Gut bacteria (especially urease-producing bacteria) convert protein → ammonia (NH3)
• Normally: portal blood carries ammonia to liver → converted to urea (urea cycle) → excreted by kidneys
• In liver failure or PSS: ammonia bypasses or overwhelms the liver → reaches the brain
• Ammonia → enters astrocytes (brain support cells) → converted to glutamine → astrocyte SWELLING → cerebral edema → neurological signs

• Manganese (deposited in basal ganglia)
• Endogenous benzodiazepines (GABA-A receptor agonists → sedation)
• Mercaptans (sulfur compounds from gut bacteria)
• Aromatic amino acids

• Head pressing against walls
• Aimless wandering / circling
• Ataxia (stumbling, wobbling)
• Blindness (cortical)
• Behavioral changes (aggression, confusion, depression)
• Hypersalivation
• Seizures (terminal sign)
• Signs often EPISODIC and worsen after protein-rich meals

• Lactulose: Laxative disaccharide that:
  1. Traps ammonia in the colon (acidifies colon → NH3 + H+ → NH4+ which cannot be absorbed)
  2. Speeds intestinal transit (flushes ammonia out)
  3. Reduces ammonia-producing bacteria
• Antibiotics (metronidazole, neomycin, rifaximin): Reduce gut bacteria that produce ammonia
• Dietary protein modification: Use HIGH-QUALITY, digestible protein (soy protein or dairy protein in dogs - soy-based diet shown beneficial); severe protein restriction is NO LONGER recommended (causes muscle wasting → more endogenous ammonia from muscle breakdown)
• Lactulose enemas: For acute HE crisis
• Treat precipitating factors: GI bleeding (blood = protein load), infection, constipation, azotemia

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3.4 MAJOR LIVER DISEASES BY SPECIES

A. CANINE LIVER DISEASES

• Progressive inflammatory disease → hepatocellular necrosis + fibrosis → eventually cirrhosis
• Causes:
  • Copper accumulation (most important recognized cause!)
  • Infectious: Leptospira interrogans (highly zoonotic!), Adenovirus type 1 (CAV-1 - Canine Infectious Hepatitis)
  • Drugs: Phenobarbital, carprofen, trimethoprim-sulfonamide
  • Idiopathic (most common after copper ruled out) - Bexfield (2017) [PMID: 28063746]
• COPPER-ASSOCIATED HEPATITIS - VERY IMPORTANT:
  • Copper normally excreted in bile; defective biliary excretion leads to hepatic accumulation
  • Bedlington Terrier - autosomal recessive mutation in COMMD1 gene → classic breed; most severe copper accumulation
  • Other predisposed breeds: Labrador Retriever, Doberman Pinscher, Dalmatian, Skye Terrier, West Highland White Terrier
  • Copper is hepatotoxic (oxidative damage) → inflammation → fibrosis → cirrhosis
  • Diagnosis: Liver biopsy with Rhodanine stain (copper stain - shows orange-red granules in hepatocytes) + quantitative copper measurement (> 2000 µg/g DW = toxic)
  • Treatment: D-penicillamine (chelates and promotes urinary excretion of copper), low-copper diet, zinc supplementation (induces metallothionein in gut, blocks copper absorption)
• Histologic criteria for CH (WSAVA Liver Standardization Group):
  • Hepatocellular apoptosis OR necrosis
  • Mononuclear or mixed inflammatory cell infiltrate
  • Regeneration
  • Fibrosis

• Hepatocytes become swollen with glycogen or fat vacuoles
• Associated with hyperadrenocorticism (Cushing's), chronic steroid use (iatrogenic Cushing's), stress
• ALP markedly elevated (often > 1000 IU/L!) while ALT is mildly elevated
• Typically benign unless underlying Cushing's is severe
• Diagnosis: Biopsy (pale vacuolated hepatocytes), low-dose dexamethasone suppression test for Cushing's

• Abnormal vessel that connects the portal circulation DIRECTLY to the systemic circulation, BYPASSING the liver
• Portal blood (full of ammonia and gut-absorbed toxins) goes straight to brain = hepatic encephalopathy
• Congenital PSS (single shunting vessel):
  • Small breeds: Yorkshire Terrier, Maltese, Shih Tzu, Miniature Schnauzer - extrahepatic shunt (outside liver)
  • Large breeds: Irish Wolfhound, German Shepherd - intrahepatic shunt (inside liver - ductus venosus fails to close)
• Acquired PSS (multiple small vessels): Develop due to chronic portal hypertension (cirrhosis)
• Classic presentation of PSS:
  • Young animal (< 2 years for congenital)
  • Small stature / failure to thrive despite eating well
  • Post-prandial (after eating) neurological signs
  • Urinary signs (ammonium biurate crystals, urolithiasis)
  • Hepatic encephalopathy signs
• Diagnosis:
  • Pre- and post-prandial bile acids - most useful screening test; very elevated (> 25 µmol/L fasted, > 50 µmol/L post-prandial)
  • Ammonia tolerance test (risky - can precipitate HE!)
  • Ultrasound: Abnormal vessel, small liver (microhepatia), diminished portal vasculature
  • Scintigraphy (nuclear scan): > 15% of portal blood going direct to systemic = significant shunting
  • CT angiography (best for surgical planning)
  • Ammonium biurate crystals in urine sediment
• Treatment:
  • Surgical (definitive): Ameroid constrictor or cellophane banding to gradually occlude the shunting vessel; allows portal blood to gradually readjust; preferred for extrahepatic shunts
  • Medical management: For poor surgical candidates, pre-surgical stabilization; lactulose + antibiotics + dietary management
  • Prognosis: GOOD with successful surgery (especially extrahepatic shunts - 85%+ long-term success)

• Unique to dogs - not reported in cats
• Accumulation of abnormally viscous bile within the gallbladder, forming a star-shaped or kiwi-shaped mucocele
• Associated with Shetland Sheepdog, Cocker Spaniel, Miniature Schnauzer, hypothyroidism, hyperadrenocorticism, dyslipidemia
• Signs: Vomiting, anorexia, jaundice, abdominal pain; can rupture → bile peritonitis (EMERGENCY!)
• Diagnosis: Ultrasound - "kiwi fruit" or "stellate" (star-shaped) pattern in gallbladder
• Treatment: Cholecystectomy (surgical gallbladder removal) before rupture; medical with ursodeoxycholic acid in stable cases
• Pathognomonic: "Kiwi fruit" sign on ultrasound

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B. FELINE LIVER DISEASES

This is arguably the most important feline liver disease to know completely.

• Cats have UNIQUE metabolic vulnerability: obligate carnivores; high protein metabolism; low capacity for hepatic lipid oxidation
• When a cat STOPS EATING (anorexia from ANY cause) for even 2-5 days:
  • Body fat stores are mobilized → triglycerides flood the bloodstream
  • Liver is overwhelmed → cannot process all the fat → fat ACCUMULATES in hepatocytes
  • Hepatocytes become bloated with fat → cannot function → cholestasis → jaundice → liver failure
  • This is the only disease where being OBESE makes you MORE vulnerable (obese cats have more fat to mobilize!)

• Any cause of anorexia in a cat: stress, pain, other illness (pancreatitis, IBD, renal disease), travel, change in environment, new pet in house
• Obesity is the #1 risk factor
• Concurrent pancreatitis very common

• Jaundice (icterus) - hallmark
• Anorexia (the cause AND the perpetuating factor)
• Vomiting
• Lethargy, depression
• Weight loss
• Hepatomegaly (enlarged liver)
• Neurological signs if HE develops
• Drooling, nausea
• Muscle wasting (hepatic failure)

• History of anorexia (2+ days in obese cat)
• Blood tests: Markedly elevated ALP (very high ALP in a CAT is SIGNIFICANT - unlike dogs, cats have low baseline ALP); elevated ALT; hyperbilirubinemia; hypokalemia; hypomagnesemia
• Ultrasound: Hyperechoic (bright white) liver - fat makes liver echogenic; hepatomegaly
• FNA (Fine Needle Aspirate) of liver - DIAGNOSTIC: shows hepatocytes stuffed with lipid vacuoles (lipid vacuolation); simple and safe to perform with ultrasound guidance
• Rule out underlying cause (blood glucose, T4, urinalysis, thoracic X-ray)

• Feeding tube placement is the cornerstone of treatment! Cat must receive adequate calories
  • Esophagostomy tube (E-tube): Preferred; easy to place, can go home with tube
  • PEG tube (Percutaneous Endoscopic Gastrostomy): For longer-term use
  • Nasogastric (NG) tube: Short-term
• Feed HIGH-PROTEIN, MODERATE-FAT diet through tube (protein stimulates lipid oxidation in cats)
• Do NOT restrict protein (despite liver disease - cats NEED protein to reverse HL)
• Supplement: Cobalamin (B12), thiamine (B1), potassium, magnesium
• IV fluids for dehydration
• Antiemetics for nausea (maropitant)
• S-Adenosylmethionine (SAMe): Antioxidant, hepatoprotectant; supports glutathione synthesis
• Vitamin E: Antioxidant
• Carnitine: Helps fat oxidation in liver
• Treat underlying cause simultaneously

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• Most common form of chronic inflammatory liver disease in cats
• Inflammation of the bile ducts (cholangitis) ± liver (cholangiohepatitis)
• THREE FORMS (important for differential diagnosis):

• Signs: Jaundice, vomiting, anorexia, weight loss, hepatomegaly, fever (neutrophilic form), abdominal pain
• Diagnosis: Chemistry (elevated ALP, ALT, GGT, bilirubin), ultrasound (thickened bile ducts, echogenic liver), liver biopsy is DEFINITIVE (tissue diagnosis essential to determine type)
• Part of Feline Triaditis with pancreatitis + IBD

• Lymphoma = most common hepatic tumor in cats (unlike dogs where hepatocellular carcinoma is #1)
• Also: bile duct carcinoma (cholangiocarcinoma), mast cell tumor, hepatocellular carcinoma

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3.5 DIAGNOSTICS FOR LIVER DISEASE (General)

Blood Biomarkers:

Imaging:

• Radiographs: Liver size and position; hepatomegaly vs. microhepatia; calcification (rare)
• Ultrasound: Parenchymal texture, echogenicity, vessel anatomy, bile duct thickness, mass lesions, ascites, PSS vessel
• Scintigraphy: Portal blood flow quantification (PSS diagnosis)
• CT angiography: Best for PSS surgical planning

Biopsy - DEFINITIVE DIAGNOSIS:

• Required to definitively diagnose type of liver disease
• Methods: Ultrasound-guided tru-cut biopsy, keyhole (laparoscopic), or exploratory laparotomy
• ALWAYS check coagulation times BEFORE biopsy (liver disease = coagulopathy = bleeding risk!)
• FNA (fine needle aspirate): Quick, minimal bleeding risk; can diagnose HL, neoplasia, but CANNOT assess architecture (can't diagnose hepatitis/fibrosis from FNA alone)

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3.6 TREATMENT OF LIVER DISEASE (General Principles)

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3.7 LIVER DISEASE COMPLICATIONS SUMMARY (Lidbury, Vet Clin North Am, 2025 [PMID: 40379581])

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3.8 EXAM / INTERVIEW QUESTIONS - LIVER DISEASE

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MASTER DIFFERENTIATION TABLE - All 3 Topics + Vomiting & Diarrhea

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REFERENCES

• Robbins & Kumar Basic Pathology - Pancreatitis pathophysiology (pages 640-641)
• Guyton & Hall Textbook of Medical Physiology - Vomiting center, GI physiology
• Armstrong PJ, Williams DA. "Pancreatitis in cats." Top Companion Anim Med. 2012 [PMID: 23148855]
• Lidbury JA, Cook AK, Steiner JM. "Hepatic encephalopathy in dogs and cats." J Vet Emerg Crit Care. 2016 [PMID: 27060899]
• Lidbury JA. "Complications of Liver Disease." Vet Clin North Am Small Anim Pract. 2025 [PMID: 40379581]
• Bexfield N. "Canine Idiopathic Chronic Hepatitis." Vet Clin North Am Small Anim Pract. 2017 [PMID: 28063746]
• DVM360: Diagnosis and Management of Megaesophagus in Dogs
• VCA Animal Hospitals: Megaesophagus
• Cornell University College of Veterinary Medicine: Liver Disorders

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Quick Summary - Kya Cover Kiya Gaya:

REGURGITATION:

• Vomiting vs. Regurgitation ka complete master table (exam mein zaroor aata hai)
• Esophageal anatomy (dogs = fully striated muscle = why MG causes megaesophagus)
• Megaesophagus - congenital + acquired causes (MG #1 cause!)
• PRAA (Persistent Right Aortic Arch) - pathognomonic for weaning-age puppies
• Bailey Chair feeding technique
• Pyridostigmine for Myasthenia Gravis

PANCREATITIS:

• Autodigestion mechanism - complete trypsin cascade
• Three pathways: Duct obstruction, Acinar cell injury, Defective intracellular transport
• Pancreatitis diagram image from Robbins & Kumar
• Prayer position in dogs = pathognomonic
• Feline Triaditis (Pancreatitis + IBD + Cholangitis)
• Miniature Schnauzer predisposition (hypertriglyceridemia)
• cPLI = gold standard diagnostic test
• Hypocalcemia = serious prognostic indicator
• Complications (EPI, DM, pseudocyst, DIC, ARDS)

LIVER DISEASE:

• Complete liver function overview
• Hepatic Encephalopathy - ammonia pathway, management (lactulose, metronidazole)
• Copper-associated hepatitis (Bedlington Terrier = COMMD1 gene)
• PSS (Portosystemic Shunt) - ammonium biurate crystals, bile acids
• Gallbladder Mucocele - "kiwi fruit" ultrasound sign
• Feline Hepatic Lipidosis - MOST IMPORTANT feline liver disease; esophagostomy tube = treatment
• Feline Cholangitis - 3 types + treatment
• Why ALP is more significant in cats than dogs
• Why protein restriction is no longer recommended in HE

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🐾 VETERINARY OPHTHALMOLOGY MASTERCLASS

CORNEAL ULCERS + KCS + ANTERIOR UVEITIS

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SECTION 1: CORNEAL ULCERS (ULCERATIVE KERATITIS)

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1.1 ANATOMY OF THE CORNEA - UNDERSTAND FIRST

OUTSIDE (Tear Film)
    ↓
1. Epithelium (5-7 cell layers thick - MOST SENSITIVE; contains pain receptors)
2. Bowman's Layer (acellular basement membrane - thin)
3. Stroma (THICKEST layer - 90% of corneal thickness; collagen fibrils + keratocytes)
4. Descemet's Membrane (basement membrane of endothelium - thin but very TOUGH)
5. Endothelium (single cell layer; contains Na-K ATPase PUMP - keeps cornea dehydrated and clear)
    ↓
INSIDE (Anterior Chamber)

• Dog cornea thickness: 0.55 mm (center), 0.65 mm (periphery)
• Cat cornea thickness: ~0.58 mm (center and periphery similar)
• The cornea is AVASCULAR (gets oxygen from tear film and aqueous humor)
• The cornea has the HIGHEST density of sensory nerve endings of any tissue in the body - this is why corneal ulcers are EXTREMELY PAINFUL
• The superficial cornea (epithelium) is the MOST sensitive layer

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1.2 DEFINITION

• An erosion = loss of only epithelium (no stromal involvement)
• An ulcer = loss of epithelium + some degree of stromal involvement

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1.3 CLASSIFICATION BY DEPTH (Most Important System!)

GRADE 1: Superficial Ulcer (Epithelial Erosion)

• Loss of epithelium ONLY
• Stroma is exposed but NOT lost
• MOST PAINFUL paradoxically - because the superficial nerve endings are exposed
• Fluorescein stain: POSITIVE (stain pools in the defect)
• Treatment: Topical antibiotics, lubricants, ± E-collar

GRADE 2: Superficial Stromal Ulcer

• Loss of epithelium + loss of superficial stroma (< 50% stromal depth)
• Risk of bacterial colonization
• Fluorescein stain: POSITIVE

GRADE 3: Deep Stromal Ulcer

• Loss of epithelium + loss of > 50% stromal depth
• THREATENS structural integrity of the eye
• Risk of rupture if progresses
• Requires aggressive treatment and possibly surgery

GRADE 4: Descemetocele

• Loss of ALL stroma - only Descemet's membrane remains as the floor of the ulcer
• Descemet's membrane does NOT absorb fluorescein dye!
• Fluorescein stain: NEGATIVE at the very center (because no stroma remains!) but POSITIVE at the edges
• This is a SURGICAL EMERGENCY - one sneeze, one paw rub, and the eye ruptures
• Pathognomonic: Negative fluorescein staining at center of deepest ulcer = Descemetocele

GRADE 5: Ruptured Globe / Corneal Perforation

• The Descemet's membrane has also ruptured
• Aqueous humor (fluid) leaks out
• Iris may prolapse through the perforation
• Globe-threatening emergency

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1.4 SPECIAL TYPES OF CORNEAL ULCERS IN VETERINARY MEDICINE

A. INDOLENT ULCER (SCCED - Spontaneous Chronic Corneal Epithelial Defect)

• Definition: A superficial ulcer that REFUSES to heal through normal wound-healing processes despite appropriate treatment, persisting for weeks to months
• Mechanism: Abnormally weak adhesion between basal epithelial cells and their basement membrane. The epithelium is present but does NOT stick down - it slides loosely over the stroma like a carpet that won't stick to the floor
• There is also an abnormal, acellular (cell-free), hyaline zone in the anterior stroma that physically prevents epithelial adhesion
• Characteristics:
  • Superficial ONLY (does not extend into stroma)
  • Has redundant, loose, non-adherent epithelial edges ("lip" of epithelium around the ulcer)
  • Characteristic "halo" staining pattern with fluorescein - the loose epithelium uptakes dye at the edges
  • May or may not have superficial corneal vascularization (blood vessels growing in)
• Affects: Middle-aged to older dogs (average 8-9 years); any breed but Boxers are classically overrepresented
• Other predisposed breeds: Golden Retriever, Labrador, Corgi, Samoyed, Poodle
• Treatment:
  1. Debridement - Gently remove all loose epithelium with a dry cotton-tipped swab or surgical sponge (don't scrape the stroma)
  2. Grid/Punctate Keratotomy - Using a 25-gauge needle, lightly score the ulcer bed in a grid pattern to break up the acellular hyaline zone and create microchannels for new blood vessels and epithelial adhesion
  3. Diamond burr keratectomy - Mechanical superficial keratectomy (preferred over grid keratotomy by ophthalmologists); removes the abnormal anterior stroma
  4. Topical broad-spectrum antibiotic (prophylactic)
  5. E-collar (Elizabethan collar - cone) - ALWAYS
  6. Oral NSAIDs for pain
  7. If grid keratotomy fails: Superficial keratectomy (surgical removal of abnormal tissue)

B. MELTING ULCER (Stromal Lysis)

• Definition: An ulcer in which bacterial-produced and host-produced enzymes (Matrix Metalloproteinases - MMPs, particularly MMP-2 and MMP-9, and bacterial proteases and collagenases) are ACTIVELY DESTROYING the corneal stroma
• The stroma dissolves like jelly - the eye can go from a small ulcer to a perforation in HOURS
• Appearance: Grey-white, gelatinous, liquefied-looking stroma at the ulcer base. Distinguished from corneal edema by its soft, jelly-like texture
• Key causative organisms: Pseudomonas aeruginosa (most aggressive collagenase producer!), Beta-hemolytic Streptococcus, Staphylococcus
• Predisposed: Brachycephalic breeds (Pugs, Bulldogs, French Bulldogs, Shih Tzu, Pekinese) due to:
  • Exophthalmos (bulging eyes) - increased exposure
  • Lagophthalmos (incomplete eyelid closure) - incomplete corneal protection
  • Macroblepharon (large palpebral fissure)
  • Reduced corneal sensation (trigeminal nerve compression)
• Why topical steroids are CONTRAINDICATED in melting ulcers:
  • Steroids INCREASE tear protease activity
  • Steroids increase collagenase activity
  • Steroids impair corneal healing
  • Using steroids on a melting ulcer = accelerating destruction
• Treatment:
  • STOP all topical steroids immediately
  • Aggressive topical antibiotics every 1-2 hours (fluoroquinolones: ciprofloxacin 0.3%, ofloxacin)
  • Antiprotease therapy: Acetylcysteine (5-10% topical solution) - N-acetylcysteine inhibits MMPs; EDTA drops; autologous serum (from the patient's own blood) - contains natural anti-proteases (alpha-2 macroglobulin)
  • Systemic doxycycline - inhibits MMPs systemically
  • Systemic NSAIDs or oral prednisolone (to reduce inflammation - NEVER topical steroids)
  • Surgical: Conjunctival pedicle graft or corneal graft if severe

C. FELINE HERPESVIRUS (FHV-1) ULCERS

• Feline Herpesvirus Type 1 is the most common cause of corneal ulcers in CATS
• FHV-1 causes direct viral lysis of corneal epithelial cells
• Initial: Dendritic (branching, tree-shaped) ulcers - pathognomonic for herpes keratitis
• Can progress to geographic (large map-like) ulcers
• May cause corneal stromal disease in chronically infected cats
• Key feature: Often BILATERAL; associated with upper respiratory signs (sneezing, nasal discharge); can be recurrent (virus stays latent in trigeminal ganglion and reactivates with stress)
• Treatment: Topical antiviral (idoxuridine 0.1%, trifluridine 1%), oral famciclovir (100-125 mg/cat every 12 hrs - drug of choice for systemic FHV treatment), L-lysine supplementation (controversial but widely used), topical lubricants

D. CORNEAL SEQUESTRUM (Feline Specific!)

• A unique condition seen ONLY in cats (not reported in dogs)
• A dark brown to black, plaque-like focus of degenerate (dead) corneal stromal tissue that forms, usually after chronic corneal trauma or FHV infection
• Appears as a brown/black opaque plaque embedded in the cornea
• Can cause chronic discomfort, tearing, blepharospasm
• Predisposed breeds: Persian, Himalayan, Siamese, Burmese (all brachycephalic cats)
• Treatment: Superficial keratectomy (surgical removal); healing usually good but recurrence possible
• Pathognomonic: Dark brown/black corneal plaque in a brachycephalic cat = Corneal Sequestrum

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1.5 CAUSES OF CORNEAL ULCERS IN DOGS AND CATS

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1.6 CLINICAL SIGNS

• Pain - blepharospasm (squinting), pawing at the eye
• Photophobia - avoiding light (due to ciliary spasm from reflex uveitis)
• Purulent/mucoid discharge
• Protrusion of nictitating membrane (third eyelid rises to protect painful eye)
• Periocular changes - conjunctival hyperemia (redness), chemosis (swollen conjunctiva)

• Epiphora (excessive tearing/watering)
• Corneal edema (blue-white haze due to fluid entering the stroma through the damaged epithelium)
• Superficial corneal vascularization (blood vessels grow into cornea from limbus - response to chronic ulceration; superficial = pink, brush-like vessels)
• Miosis (constricted pupil) - from reflex anterior uveitis (the pain signals trigger uveitis)
• Aqueous flare (protein in anterior chamber) - from secondary uveitis

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1.7 DIAGNOSIS

Step 1: Schirmer Tear Test (STT) FIRST

• Always do STT BEFORE instilling any drops!
• Rules out KCS as the underlying cause
• Normal: > 15 mm/minute in dogs; > 10 mm/minute in cats
• If STT is low, treat KCS simultaneously

Step 2: Fluorescein Stain - THE MOST IMPORTANT TEST

• Fluorescein is a water-soluble, orange dye that is hydrophilic (water-loving)
• It is REPELLED by the intact lipid-based epithelium (normally)
• It is ATTRACTED to and pools in any area where epithelium is lost (stroma is hydrophilic = loves water = takes up dye)
• Application: Place fluorescein strip in lower conjunctival sac; flush with sterile saline; examine under cobalt blue light (dye fluoresces bright GREEN under blue light)
• Positive stain = Green fluorescence = Epithelial defect PRESENT = Ulcer confirmed
• Descemetocele: NEGATIVE at the center (no stroma to take up dye!) but POSITIVE ring at the edges
• Use cobalt blue light - routine white light examination misses subtle ulcers

Step 3: Tonometry (IOP measurement)

• Check intraocular pressure (IOP)
• Uveitis usually causes LOW IOP (ciliary body shutdown)
• If IOP is HIGH in an inflamed eye = secondary glaucoma = serious complication

Step 4: Additional Tests

• Corneal cytology: Sample from ulcer margin - look for bacteria, neutrophils, fungal hyphae
• Bacterial culture and sensitivity: From deep/infected ulcers before starting antibiotics
• Rose Bengal stain: Stains dead or devitalized epithelial cells; useful for early FHV dendritic ulcers
• Slit-lamp biomicroscopy: Detailed examination of ulcer depth, corneal layers
• Complete ocular examination: Rule out entropion, distichiasis, foreign body, ectopic cilia

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1.8 TREATMENT BY ULCER TYPE

All Corneal Ulcers - General Principles:

• Prevent/treat secondary bacterial infection
• Choices: Triple antibiotic (neomycin-polymyxin-bacitracin), tobramycin 0.3%, ofloxacin 0.3%, ciprofloxacin 0.3% (fluoroquinolones for infected/deep ulcers)
• Frequency: Every 4-6 hours for superficial; every 1-2 hours for melting ulcers
• NEVER use aminoglycosides (gentamicin, tobramycin) as SOLE treatment - Pseudomonas can be resistant

• Use when REFLEX UVEITIS is present (miosis, aqueous flare, severe photophobia)
• Mechanism: Parasympatholytic → dilates pupil (mydriasis) + paralyzes ciliary muscle (cycloplegia)
• Benefits: Relieves pain from ciliary spasm; prevents posterior synechiae (iris sticking to lens)
• Frequency: Every 8-24 hours until pupil dilated, then taper
• CONTRAINDICATED if IOP is elevated (will worsen glaucoma!)
• CONTRAINDICATED if KCS is present (decreases tear production further)
• In cats: Use atropine OINTMENT only (not drops) - drops drain to nasopharynx → extremely bitter taste → excessive salivation, frothing, vomiting

• Prevents self-trauma (pawing, rubbing)
• Most critical single instruction to give the owner!
• "If you take the cone off, the eye will get worse."

• Meloxicam or carprofen for pain
• Corneal ulcers are very painful

• Topical corticosteroids on any ulcer - impair healing, increase risk of infection, worsen melting
• Topical anesthetics (proxymetacaine, tetracaine) as dispensed medications - epitheliotoxic; delay healing; mask pain that protects the eye

Surgical Options for Deep/Non-Healing Ulcers:

• Conjunctival pedicle graft: Brings blood supply and antiproteases to the ulcer; preferred for deep/melting ulcers
• Corneoconjunctival transposition
• Corneal graft (when > 50% stromal depth lost)
• Temporary tarsorrhaphy (sewing eyelids partially together) - provides protection for healing
• Enucleation (eye removal) - for ruptured globes with no vision potential

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1.9 KEY DIFFERENTIATIONS

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SECTION 2: KERATOCONJUNCTIVITIS SICCA (KCS) - DRY EYE SYNDROME

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2.1 DEFINITION

• KCS = "Kera" (cornea) + "to" + "conjunctivitis" (conjunctival inflammation) + "Sicca" (Latin for DRY)
• Also known simply as "Dry Eye Syndrome"
• Very common in dogs (annual incidence 0.3-1.52% in North America)
• Uncommon in cats (cats have primarily lipid-deficient tear film disease instead)

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2.2 THE TEAR FILM - UNDERSTAND THOROUGHLY

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2.3 PATHOPHYSIOLOGY

1. CD4+ T-lymphocytes (helper T-cells) infiltrate the lacrimal gland tissue
2. They attack and destroy lacrimal acinar cells (the secretory cells that make aqueous tears)
3. Progressive glandular atrophy and fibrosis
4. Tear production drops → aqueous layer becomes insufficient
5. Corneal surface dries → epithelial cell death, corneal ulceration, chronic inflammation
6. Goblet cells (mucin producers) also affected → mucin becomes thick and stringy
7. Result: thick, ropy, mucopurulent (mucous + pus) discharge

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2.4 CAUSES OF KCS IN DOGS

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2.5 BREED PREDISPOSITIONS

• English Bulldog, American Cocker Spaniel - highest prevalence (up to 30% lifetime risk!)
• West Highland White Terrier
• Yorkshire Terrier (also congenital alacrima)
• Shih Tzu, Lhasa Apso, Pekingese
• Cavalier King Charles Spaniel
• Pug
• Boston Terrier
• Miniature Schnauzer
• Bloodhound

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2.6 CLINICAL SIGNS

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2.7 DIAGNOSIS

Schirmer Tear Test (STT) - THE DIAGNOSTIC TEST

1. Before ANY eye drops, without topical anesthetic
2. Fold standardized Whatman filter paper strip at notch
3. Place hooked end in LOWER conjunctival sac (not touching cornea)
4. Close eyelids gently around strip
5. Wait EXACTLY 60 seconds
6. Read wetted length in millimeters

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2.8 TREATMENT

First-Line: Immunomodulatory Therapy (Tear Stimulants)

• Calcineurin inhibitor (blocks calcineurin enzyme in T-cells)
• Blocks transcription of cytokine genes (IL-2, IL-4, IFN-gamma) in activated T-cells
• Prevents T-cell activation and proliferation
• Reduces T-cell-mediated destruction of lacrimal gland
• ALSO directly stimulates lacrimogenesis (tear production) - possibly via effects on prolactin receptors
• Isolated from fungus Tolypocladium inflatum (1976)

• 0.2% ointment (Optimmune) - twice daily (every 12 hours)
• Compounded 1-2% cyclosporine in olive/corn oil if 0.2% insufficient
• Allow 30-45 days minimum for full response
• If STT improves > 20 mm/min: can reduce to once daily for maintenance
• Lifelong treatment required (stopping causes relapse)

• 50-80% of dogs respond to 0.2% CsA
• Severely affected dogs (STT 0-5 mm/min) may respond less well
• Must evaluate after 6-8 weeks before declaring failure

• 100 times MORE POTENT than cyclosporine
• Used as 0.02%-0.03% ophthalmic solution or ointment
• Dogs that fail cyclosporine may respond to tacrolimus
• Studies show tacrolimus is as effective as cyclosporine; some suggest superior in non-responders
• Compounded in olive oil for better bioavailability

• Macrolide immunosuppressant; similar mechanism to tacrolimus
• Less commonly used in veterinary medicine

• Newer option; 0.02% aqueous topical solution
• Different mechanism (mTOR inhibition, not calcineurin)
• Has shown increased tear production in dogs

Second-Line: Tear Film Supplementation

• Methylcellulose, carbomer, hyaluronic acid (sodium hyaluronate) - based ocular lubricants
• Provide temporary relief; do NOT treat underlying cause
• Must be used frequently (every 1-4 hours) - impractical as sole treatment
• Use as ADJUNCT to immunomodulators, especially initially when tear stimulants haven't started working yet

Third-Line: Additional Medications

• SPECIFICALLY for NEUROGENIC KCS (nerve damage causing reduced lacrimation)
• Stimulates the parasympathetic receptors on lacrimal gland to secrete tears
• Oral pilocarpine: 1-2 drops of 2% solution on food, 2-3x daily
• Topical: 0.1-0.2% dilute pilocarpine ophthalmic drops
• Side effects: vomiting, diarrhea, salivation (if too high a dose)

• Break up thick, ropy mucoid discharge
• Make it easier to clear

• For secondary bacterial conjunctivitis and corneal ulceration

• Used short-term if no ulcer present - reduces conjunctival inflammation
• Prednisolone acetate 1% or dexamethasone 0.1%
• NEVER use if corneal ulcer is present

Surgical Options (Refractory Cases)

• Surgically redirect the parotid salivary gland duct to open in the conjunctival sac instead of the mouth
• Saliva then wets the eye!
• Works reasonably well but complications include:
  • Mineral deposits on cornea (calcium salts in saliva) especially when animal eats/drinks
  • Overflow when eating (food smell stimulates salivation → eye wets excessively)
  • Requires careful client education

• Slow-release CsA implant placed under conjunctiva
• Provides 18 months of tear stimulation from single procedure

• For end-stage, blind, painful eyes that cannot be managed medically

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2.9 PROGNOSIS

• Early diagnosis + lifelong cyclosporine: EXCELLENT - vision preserved, comfort maintained
• Delayed treatment: Risk of permanent corneal scarring, pigmentation, and BLINDNESS
• Neurogenic KCS (pilocarpine-responsive): Variable; depends on whether nerve damage recovers
• Drug-induced (sulfonamides): May be irreversible even after stopping the drug

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SECTION 3: ANTERIOR UVEITIS (IRIDOCYCLITIS)

═══════════════════════════════════════

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3.1 ANATOMY OF THE UVEAL TRACT

ANTERIOR UVEA:
  ├── Iris (colored ring around pupil; contains sphincter and dilator pupillae muscles)
  └── Ciliary Body (produces aqueous humor; controls lens accommodation; contains ciliary muscle)

POSTERIOR UVEA:
  └── Choroid (vascular layer between retina and sclera; nourishes retina)

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3.2 PATHOPHYSIOLOGY

1. The trigger (trauma, infection, immune activation, tumor) causes inflammation
2. Prostaglandins (PGE2), histamine, cytokines, and leukotrienes are released
3. These inflammatory mediators BREAK DOWN the Blood-Aqueous Barrier
4. Blood vessels become hyperpermeable (leaky)
5. Plasma PROTEINS leak into the anterior chamber → Aqueous Flare (cloudy, hazy aqueous)
6. White blood cells (WBCs) migrate into the anterior chamber → Aqueous Cells
7. Fibrin may leak in → Fibrin clots in anterior chamber
8. If severe: WBCs settle gravitationally → Hypopyon (white layer of cells at bottom of anterior chamber)
9. If blood vessels rupture: Hyphema (blood in anterior chamber - red)

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3.3 CLINICAL SIGNS - "THE UVEITIS SIGN GRID"

MUST KNOW: 8 Classic Signs of Anterior Uveitis

Additional Signs:

• Keratic precipitates (KPs): WBC aggregates deposited on the posterior corneal endothelium; appear as white dots on back of cornea (especially in cats)
  • Fine KPs = lymphocytes, plasma cells (chronic, immune-mediated)
  • Mutton-fat KPs (large, greasy) = macrophages + epithelioid cells (granulomatous uveitis - FIP, blastomycosis)
• Hypopyon (white cells layer at bottom of anterior chamber) - severe inflammation
• Hyphema (blood in anterior chamber) - rupture of inflamed iris vessels
• Rubeosis iridis (new blood vessels on iris surface) - chronic uveitis
• Iris color change (darker, "muddy" iris) - inflamed iris changes appearance
• Posterior synechiae (iris adheres to anterior lens capsule) - inflammatory fibrin glues iris to lens
• Iris bombe - complete 360° posterior synechiae → aqueous humor cannot flow through pupil → builds up behind iris → pushes iris forward → acute angle closure glaucoma
• Secondary glaucoma - trabecular meshwork blocked by inflammatory cells and debris

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3.4 CAUSES OF ANTERIOR UVEITIS

OCULAR (Primary / Reflex) CAUSES

SYSTEMIC (Infectious) CAUSES

IMMUNE-MEDIATED CAUSES

• Autoimmune attack against melanocytes (pigment-containing cells) in uvea AND skin
• Bilateral granulomatous panuveitis + depigmentation of skin/nose/lips/eyelids
• Most commonly affected: Akita Inu, Siberian Husky, Samoyed, Chow Chow, Shetland Sheepdog
• Treatment: Aggressive, long-term immunosuppression (prednisolone + azathioprine)
• Pathognomonic: Bilateral panuveitis + vitiligo (depigmentation) of nose/lips in an Akita = Uveodermatologic syndrome

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3.5 DIAGNOSIS

Step 1: Complete Ophthalmic Examination

• Slit-lamp biomicroscopy - gold standard for detecting flare, cells, KPs, synechiae
• Tonometry - check IOP (LOW = uveitis; HIGH = secondary glaucoma)
• Indirect ophthalmoscopy - examine retina (choroidal lesions, retinal detachment)
• Fluorescein stain - rule out concurrent corneal ulcer

Step 2: Minimum Database (Blood Work)

• CBC: Lymphocytosis (viral), thrombocytopenia (tick-borne diseases - Ehrlichia!), anemia
• Chemistry panel: BUN/creatinine (leptospirosis), liver enzymes
• Urinalysis: Proteinuria (leptospirosis, FIP)

Step 3: Disease-Specific Tests

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3.6 COMPLICATIONS OF UNTREATED/CHRONIC UVEITIS

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3.7 TREATMENT

1. Relieve pain (blepharospasm, photophobia, ciliary spasm)
2. Reduce inflammation (prevent BAB breakdown)
3. Prevent synechiae (iris-lens adhesion)
4. Prevent secondary glaucoma
5. Treat the underlying cause

Topical Therapy:

• Prednisolone acetate 1% (best penetration - lipophilic; passes through cornea efficiently) - FIRST LINE
• Dexamethasone 0.1% - alternative
• Dosing: Every 3-6 hours initially (severe); taper over weeks as inflammation resolves
• CONTRAINDICATED if corneal ulcer present (will prevent healing and worsen ulcer)

• Diclofenac 0.1%, flurbiprofen 0.03%, ketorolac 0.5%
• Use when steroids contraindicated (concurrent corneal ulcer)
• Less potent than steroids but safe with ulcers

• Mechanism:
  • Cycloplegia (paralyzes ciliary muscle) → relieves pain from ciliary spasm
  • Mydriasis (dilates pupil) → breaks early posterior synechiae; prevents new synechiae formation
  • Stabilizes blood-aqueous barrier (reduces permeability of iris vessels)
• Dosing: Every 8-24 hours; reduce to every 24-48 hours when pupil fully dilated
• Monitor IOP - if IOP rises, STOP atropine (mydriasis worsens glaucoma by crowding the drainage angle)
• Use ointment in cats - avoid bitter drops draining to pharynx (salivation, nausea)
• AVOID in KCS - reduces already deficient tear production
• AVOID in secondary glaucoma - will worsen the pressure

Systemic Therapy:

• Prednisolone 1-2 mg/kg/day orally
• Indicated for: severe anterior uveitis, posterior uveitis, panuveitis, immune-mediated causes (uveodermatologic syndrome)
• AVOID or use cautiously if systemic infectious disease suspected (leptospirosis, brucellosis, systemic fungal) - will worsen infection
• Start topical steroids even in suspected infections - protect the eye

• Meloxicam, carprofen, aspirin
• For mild-moderate uveitis, especially if systemic steroids contraindicated
• Aspirin in cats: Use with EXTREME CAUTION - toxic at high doses; low-dose only

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MASTER COMPARISON TABLE - ALL 3 DISEASES

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IMPORTANT EXAM & INTERVIEW QUESTIONS

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• 15 mm/min = Normal

• 11-14 = Borderline
• 6-10 = Mild-moderate KCS
• 0-5 = SEVERE KCS Diagnosis of KCS requires STT-I < 10 mm/min combined with compatible clinical signs.

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• Dogs: Bacterial most common: Staphylococcus pseudintermedius, Streptococcus, Pseudomonas aeruginosa (most dangerous - produces collagenase, causes melting ulcers)
• Cats: Feline Herpesvirus-1 (FHV-1) is the most common cause of corneal ulcers in cats; also bacteria (Staphylococcus, Streptococcus), Mycoplasma
• Fungal ulcers are uncommon in both species but seen in immune-suppressed patients or those on chronic topical steroids

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REFERENCES

• Tintinalli's Emergency Medicine - Corneal Ulcer section
• Kanski's Clinical Ophthalmology 10th Edition - KCS, Anterior Uveitis
• Merck Veterinary Manual - Anterior Uveitis in Small Animals; KCS; Equine Recurrent Uveitis
• Today's Veterinary Practice - "When Is It Indolent? Diagnosis and Treatment of Indolent Corneal Ulcers" (2023)
• University of Florida Small Animal Hospital - Corneal Ulceration handout
• PMC: "Immune-mediated KCS in dogs: current perspectives on management" [PMC6067592]
• PMC: "Tacrolimus vs Cyclosporine in KCS dogs" [PMC3103853]
• MedVet - Uveitis in Dogs and Cats
• Today's Veterinary Practice - "Managing Uveitis in Dogs and Cats"
• Vettimes - "Corneal Ulcers Update in Canine and Feline Pets" (2023)
• Belknap EB. "Corneal Emergencies." Top Companion Anim Med. 2015 [PMID: 26494498]Yeh complete masterclass guide hai! Quick summary of what's covered:

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✅ Coverage Summary

🔵 CORNEAL ULCERS:

• 5 layers of cornea explained with diagram
• 4 grades by depth - Superficial → Stromal → Descemetocele → Perforation
• Special types: SCCED/Indolent (Boxer Ulcer), Melting Ulcer (Pseudomonas!), FHV-1 Dendritic Ulcers (cats), Corneal Sequestrum (cats only - black plaque)
• Fluorescein stain - how it works, why Descemetocele is NEGATIVE center
• Why NEVER give topical anesthetics home
• Brachycephalic breed predisposition
• Treatment: antibiotics, atropine, E-collar, anti-proteases for melting

🟡 KCS (DRY EYE):

• 3-layer tear film explained
• Immune-mediated T-cell destruction of lacrimal gland = main cause
• Schirmer Tear Test - values, technique, normal vs. abnormal
• Cyclosporine A (Optimmune) - mechanism (calcineurin inhibitor), dosing, brand name
• Tacrolimus - 100x more potent than CsA
• Breed predispositions (Cocker Spaniel, Bulldog)
• Sulfonamide drugs as a cause
• Parotid duct transposition surgery

🔴 ANTERIOR UVEITIS:

• Uveal tract anatomy (iris + ciliary body + choroid)
• Blood-Aqueous Barrier breakdown = core pathophysiology
• 8 classic signs including MIOSIS + LOW IOP + AQUEOUS FLARE
• KPs (Keratic Precipitates) - fine vs. mutton-fat
• Causes in dogs (Leptospira, Brucella, tick-borne) vs. cats (FIP, FeLV, FIV, Toxoplasma)
• Uveodermatologic Syndrome (Akita + vitiligo = pathognomonic)
• Lens-Induced Uveitis (cataracts leak protein)
• Treatment: prednisolone acetate 1% + atropine (ointment in cats!)
• Complications: Synechiae → Iris Bombe → Glaucoma → Phthisis Bulbi

CKD study map

1. Core concepts and renal physiology
   What CKD means, nephron loss, glomerular filtration rate (GFR), azotemia, uremia, and why CKD is progressive.
2. Causes and risk factors in dogs and cats
   Congenital disease, chronic interstitial nephritis, pyelonephritis, glomerular disease, toxins, hypertension, breed risks, and age-related disease.
3. Clinical signs and pathophysiology
   Polyuria-polydipsia (PU/PD), weight loss, dehydration, vomiting, anemia, hypertension, proteinuria, metabolic acidosis, hyperphosphatemia, hypokalemia, and uremic oral ulcers.
4. Diagnostic approach and differentials
   Urinalysis, urine specific gravity, SDMA, creatinine, UPC ratio, blood pressure, ultrasound, culture, and differentiation from acute kidney injury, pre-renal azotemia, post-renal obstruction, diabetes, and hyperthyroidism.
5. IRIS staging and substaging
   How to stage stable CKD using creatinine or SDMA, then substage by proteinuria and systemic blood pressure.
6. Treatment plan by problem
   Renal diet, hydration, antiemetics, phosphate binders, potassium, antihypertensives, antiproteinuric drugs, anemia management, acid-base correction, and treatment of urinary infection.
7. Species-specific CKD
   Important differences between dogs and cats, including feline hypokalemia and hypertension, and canine protein-losing nephropathy.
8. Monitoring, prognosis, client communication, and cases
   Recheck plans, quality-of-life assessment, emergency red flags, practical client advice, and exam/interview questions.

High-level overview

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🐾 VOMITING & DIARRHEA IN VETERINARY MEDICINE

A Complete Conceptual Guide for Veterinary Students & Practitioners

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PART 1: VOMITING (EMESIS)

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1.1 DEFINITION

• Vomiting - active process, preceded by nausea and retching
• Regurgitation - passive process, no abdominal effort, no nausea (covered in differentiation section)

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1.2 ANATOMY OF THE VOMITING REFLEX - PATHOPHYSIOLOGY

The "Vomiting Center" (Emetic Center)

The Chemoreceptor Trigger Zone (CTZ)

• It lies OUTSIDE the blood-brain barrier (BBB) - so blood-borne toxins, drugs, and metabolic waste products can reach it directly
• Dogs have a very sensitive CTZ (dogs vomit easily; cats are more resistant)
• Key receptors: D2 (dopamine), 5-HT3 (serotonin), NK1 (neurokinin/substance P), alpha-2 adrenergic, opioid receptors

Step-by-Step Mechanism of the Vomiting Act

1. Antiperistalsis begins - Retrograde peristalsis starting as far down as the ileum pushes contents back to stomach/duodenum in 3-5 minutes
2. Distension of duodenum triggers the actual vomiting act
3. Deep breath is taken
4. Hyoid bone and larynx rise - opens upper esophageal sphincter
5. Glottis closes - prevents aspiration of vomitus into lungs
6. Soft palate rises - closes posterior nares (prevents nasal expulsion)
7. Diaphragm contracts downward simultaneously with abdominal wall muscles - squeezes stomach like a vice
8. Lower esophageal sphincter (cardia) relaxes completely
9. Gastric contents expelled through esophagus and out

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1.3 CLASSIFICATION OF VOMITING

By Duration

By Timing/Character (Clinically Important!)

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1.4 CAUSES OF VOMITING IN DOGS AND CATS

PRIMARY (GI) CAUSES

• Dietary indiscretion (garbage eating, coprophagia) - most common cause in dogs
• Rapid eating / overeating
• Sudden diet change
• Food intolerance / food allergy

• Canine Parvovirus (CPV-2) - most serious viral cause in young dogs; hemorrhagic vomiting + diarrhea
• Canine Distemper Virus
• Feline Panleukopenia (feline parvovirus) - cats
• Canine Coronavirus
• Rotavirus
• Salmonella, Campylobacter, Clostridium perfringens (bacterial)
• Helicobacter pylori (gastric spiral bacteria)
• Giardia, Cryptosporidium, Toxocara (roundworms), Hookworms

• Foreign body (linear or non-linear)
• Gastric Dilatation-Volvulus (GDV) - emergency in large breed dogs
• Intussusception (telescoping of intestine into itself)
• Pyloric stenosis / hypertrophic pyloric gastropathy
• Intestinal obstruction
• Mesenteric volvulus

• Gastritis (acute or chronic)
• Gastric ulceration (NSAID-induced, mast cell tumor, Helicobacter)
• Inflammatory Bowel Disease (IBD)
• Pancreatitis (very common in dogs, particularly Miniature Schnauzers)
• Cholangiohepatitis (cats)
• Peritonitis

SECONDARY (EXTRA-GI / SYSTEMIC) CAUSES

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1.5 CLINICAL SIGNS / HISTORY TO COLLECT

• Nausea: drooling (hypersalivation), lip-licking, repeated swallowing, restlessness, grass eating
• Retching: rhythmic abdominal contractions before expulsion

1. When did it start? (acute vs. chronic)
2. How often? (frequency)
3. What does the vomit look like? (content, color, blood?)
4. Relation to feeding?
5. Access to garbage, toxins, foreign objects?
6. Other signs? (diarrhea, weight loss, PU/PD [polyuria/polydipsia], lethargy)
7. Vaccination status?
8. Current medications?
9. Deworming history?
10. Travel history / exposure to other animals?

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1.6 PHYSICAL EXAMINATION

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1.7 DIAGNOSTICS FOR VOMITING

Minimum Database

• CBC (Complete Blood Count): Leukocytosis (infection/inflammation), neutropenia (parvovirus!), anemia (GI blood loss), thrombocytopenia
• Biochemistry panel: BUN/creatinine (renal), ALT/ALP (hepatic), glucose (DKA), calcium, electrolytes
• Urinalysis: Isosthenuria (renal), glucosuria (DKA), proteinuria
• Fecal exam: Parasites, parvovirus antigen test
• Electrolytes: Hyponatremia + hyperkalemia = classic Addison's pattern; Na:K ratio < 27:1 is suspicious

Advanced Diagnostics

• Abdominal radiographs (X-rays): Foreign body, gas patterns, obstruction, GDV ("double-bubble" sign), intussusception
• Abdominal ultrasound: Mass lesions, pancreatic changes, intussusception (target sign), wall thickening, lymphadenopathy, free fluid
• Gastroscopy/endoscopy: Direct visualization, biopsy
• SNAP Parvo test: Rapid fecal antigen test for CPV
• Serum cPLI (canine Pancreatic Lipase Immunoreactivity): For pancreatitis
• ACTH stimulation test: For hypoadrenocorticism
• Serum T4: Hyperthyroidism (cats > 8 years)
• Bile acids (pre- and post-prandial): Portosystemic shunt, hepatic dysfunction
• Serum B12 (cobalamin) / folate: Chronic GI malabsorption

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1.8 TREATMENT OF VOMITING

Immediate Stabilization

1. IV fluid therapy - correct dehydration, electrolyte imbalances, acid-base disturbances
   • Use Lactated Ringer's (LR) or Normal Saline based on electrolyte status
   • Hypokalemia: add KCl supplementation to fluids
   • Metabolic alkalosis (from pyloric obstruction): correct with NS + KCl

Antiemetics (Anti-vomiting drugs)

Gastroprotectants

• Omeprazole (PPI): Best gastric acid suppression; prevents ulcers
• Famotidine (H2 blocker): Less potent than PPI
• Sucralfate: Coats ulcers; excellent for gastric/esophageal ulcers (give separately from other meds - binds them!)

Dietary Management

• NPO (Nil Per Os - nothing by mouth): Short fasts (2-4 hours) then bland diet (boiled chicken + rice)
• Early enteral nutrition is now preferred over prolonged fasting - supports gut mucosal integrity
• Avoid in obstruction (must be ruled out first!)

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PART 2: DIARRHEA

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2.1 DEFINITION

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2.2 PATHOPHYSIOLOGY - THE 4 MECHANISMS OF DIARRHEA

Mechanism 1: OSMOTIC DIARRHEA

• Mechanism: Non-absorbed osmotically active substances remain in the intestinal lumen, drawing water in by osmosis
• Causes: Lactose intolerance, maldigestion (exocrine pancreatic insufficiency - EPI), malabsorption, overfeeding of fermentable carbohydrates, lactulose
• Key feature: Stops when animal fasts (stops eating) - "fast-responsive diarrhea"
• Fecal osmolar gap: HIGH (measured osmolarity much higher than calculated)

Mechanism 2: SECRETORY DIARRHEA

• Mechanism: Active secretion of water and electrolytes INTO the lumen by enterocytes, driven by bacterial toxins, bile acids, fatty acids, or inflammatory mediators (e.g., prostaglandins, VIP)
• Causes: Cholera toxin (activates adenylyl cyclase -> cAMP -> Cl- secretion), E. coli enterotoxin, Clostridium perfringens, bile acid malabsorption, VIPoma (rare)
• Key feature: Does NOT stop with fasting (secretion continues even on empty gut)
• Produces large volumes of watery diarrhea

Mechanism 3: INCREASED MUCOSAL PERMEABILITY (Exudative / Protein-losing)

• Mechanism: Damage to the intestinal epithelium allows leakage of plasma proteins, blood, and inflammatory cells into the lumen
• Causes: Parvovirus, IBD, intestinal lymphoma, ulceration, intussusception, severe parasitism, Protein-Losing Enteropathy (PLE)
• Key feature: Hypoproteinemia (low albumin + low globulins - pan-hypoproteinemia), possible edema, ascites
• Diarrhea is often bloody or contains mucus

Mechanism 4: ABNORMAL MOTILITY

• Mechanism: Either too fast (hypermotility) - reduced contact time, inadequate absorption; or too slow (hypomotility/ileus) - bacterial overgrowth, fermentation, gas
• Causes (hypermotility): Psychogenic stress, hyperthyroidism (cats), irritable bowel syndrome (IBS)
• Causes (hypomotility): Post-operative ileus, peritonitis, hypokalemia, opioid use

Note from Today's Veterinary Practice: In most small animal diseases, MULTIPLE mechanisms contribute simultaneously, and osmotic forces plus mucosal permeability changes are the most common in dogs and cats.

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2.3 SMALL BOWEL vs. LARGE BOWEL DIARRHEA - CRITICAL DIFFERENTIATION

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2.4 CAUSES OF DIARRHEA IN DOGS AND CATS

DIETARY

• Dietary indiscretion (most common acute cause)
• Sudden diet change
• Food intolerance / allergy (beef, dairy, wheat most common)
• Garbage intoxication (enterotoxins from spoiled food)
• Overfeeding

INFECTIOUS

• Canine Parvovirus (CPV-2): Hemorrhagic diarrhea, vomiting, severe leukopenia (neutropenia!), panleukopenia in puppies; targets rapidly dividing crypt cells of intestine
• Feline Panleukopenia Virus (FPV): Cats; same parvovirus family; similar clinical signs
• Canine Coronavirus (CCV): Milder than parvovirus; often concurrent
• Rotavirus: Young animals mainly

• Salmonella spp.: Zoonotic! Bloody diarrhea, fever, septicemia risk
• Campylobacter jejuni: Common in puppies/kittens from shelters; watery to bloody diarrhea; zoonotic!
• Clostridium perfringens: Produces CPE and NetF toxins; associated with AHDS in dogs
• Clostridium difficile: Similar to humans; especially after antibiotic use
• E. coli (pathogenic strains)
• Yersinia enterocolitica

• Giardia: Pale, greasy, soft stools; small bowel; very common in young animals and shelters; zoonotic!
• Cryptosporidium: Watery diarrhea; immunocompromised risk; zoonotic!
• Toxocara canis/cati (Roundworms): Young animals; pot-bellied appearance
• Ancylostoma (Hookworms): Blood-sucking; anemia + bloody diarrhea; zoonotic!
• Trichuris vulpis (Whipworms): Large bowel diarrhea + hematochezia in dogs; typically not in cats
• Tritrichomonas foetus: Cats (especially Bengals); large bowel diarrhea; resistant to many drugs

• Histoplasma capsulatum (endemic regions)
• Pythium insidiosum (pythiosis - subtropical regions)

INFLAMMATORY / IMMUNE-MEDIATED

• Inflammatory Bowel Disease (IBD): Lymphoplasmacytic, eosinophilic, or granulomatous infiltration; chronic, often concurrent vomiting; requires biopsy for diagnosis
• Protein-Losing Enteropathy (PLE): End-result of severe intestinal disease (IBD, lymphoma, lymphangiectasia); marked hypoproteinemia, edema, ascites
• Lymphocytic-Plasmacytic Enteritis: Most common form of IBD
• Eosinophilic Gastroenteritis: Often food-triggered; eosinophilia may be present

STRUCTURAL / MECHANICAL

• Intussusception (telescoping of bowel - classic in puppies after parvovirus infection!)
• Foreign body (linear: string in cats is CLASSIC; causes plication of intestines)
• Intestinal volvulus
• Rectal polyps (large bowel)

MALABSORPTIVE / MALDIGESTIVE

• Exocrine Pancreatic Insufficiency (EPI): Insufficient digestive enzymes; classic signs = profuse, yellowish, greasy, voluminous diarrhea, weight loss despite ravenous appetite; common in German Shepherds
• Small Intestinal Bacterial Overgrowth (SIBO): Now termed Antibiotic-Responsive Diarrhea (ARD); deconjugated bile acids cause osmotic + secretory diarrhea; responds to tylosin or metronidazole
• Intestinal lymphangiectasia (protein-losing; dilated lymphatics; chylous ascites)

SYSTEMIC / METABOLIC

• Hypoadrenocorticism (Addison's): Chronic intermittent diarrhea + vomiting; Na:K ratio < 27:1; "great imitator"
• Renal failure (uremic enteritis)
• Liver failure (bile acid dysregulation)
• Hyperthyroidism (cats) - hypermotility
• DKA (osmotic diarrhea from glycosuria)

NEOPLASTIC

• Intestinal lymphoma (most common GI tumor in cats!)
• Adenocarcinoma
• Mast cell tumor (histamine causes gastric hypersecretion and diarrhea)
• Leiomyosarcoma, GIST

SPECIAL ENTITY: Acute Hemorrhagic Diarrhea Syndrome (AHDS)

• Sudden onset of severe hemorrhagic diarrhea (often "raspberry jam" consistency)
• Marked hemoconcentration: PCV (packed cell volume) can reach 60-75%+ while total protein remains NORMAL (plasma protein stays in vessels but fluid leaks out)
• Associated with netF-positive Clostridium perfringens type A
• Predilection for small/toy breeds (Miniature Poodle, Miniature Schnauzer, Yorkshire Terrier)
• Treatment: IV fluids (primary), antibiotics (ampicillin or metronidazole); antiemetics; most recover within 24-48 hours
• Key differentiator: PCV very high but TP normal (vs. hemorrhage where both drop!)

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2.5 CLINICAL SIGNS AND HISTORY

• Character of stool: watery, soft, mucoid, bloody?
• Small bowel vs. large bowel signs (use the table above)
• Tenesmus vs. polyuria/polydipsia
• Weight loss (suggests chronic / malabsorptive disease)
• Appetite: increased with EPI (ravenous but losing weight); decreased with IBD/neoplasia
• Other animals or humans affected? (suggests zoonotic cause - Salmonella, Campylobacter, Giardia)
• Deworming / vaccination history

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2.6 METABOLIC CONSEQUENCES OF DIARRHEA

Metabolic acidosis develops from: (1) loss of bicarbonate-rich intestinal secretions, (2) hypovolemia causing anaerobic metabolism and lactic acidosis. - (Ngwenyama, Vet Clin North Am Small Anim Pract, 2026)

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2.7 DIAGNOSTICS FOR DIARRHEA

Minimum Database

• CBC: Leukocytosis (bacterial/inflammatory), neutropenia + lymphopenia (parvovirus!), eosinophilia (parasites, eosinophilic enteritis), anemia (chronic blood loss - hookworms, IBD)
• Biochemistry: Total protein/albumin (low = PLE), glucose, BUN, liver enzymes, electrolytes
• Urinalysis
• Fecal flotation + direct smear: Parasites (ova, larvae, trophozoites)
• Fecal culture: Salmonella, Campylobacter
• SNAP Giardia antigen test
• SNAP Parvo antigen test

Advanced

• Serum TLI (Trypsin-Like Immunoreactivity): Diagnostic test for EPI - low TLI = EPI; high = pancreatitis
• Serum cPLI/fPLI: Pancreatitis
• Serum cobalamin (B12) and folate: B12 low = terminal ileal disease or SIBO; folate high = SIBO; both low = diffuse small bowel disease
• Serum albumin: PLE (< 2.0 g/dL severe)
• Abdominal radiographs + ultrasound
• Endoscopy + biopsy: Definitive for IBD, lymphoma (requires FULL-THICKNESS biopsy for diffuse infiltrative lymphoma)
• PARR (PCR for Antigen Receptor Rearrangements): Differentiates IBD from alimentary lymphoma

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2.8 TREATMENT OF DIARRHEA

Fluid Therapy - Phased Approach (2026, Ngwenyama)

1. Resuscitation: Rapid IV fluid boluses for hypovolemic shock (crystalloids - LRS, NS, or Plasma-Lyte)
2. Optimization: Correct remaining deficits over 12-24 hours; add KCl to fluids for hypokalemia
3. Stabilization: Maintenance rate; monitor electrolytes frequently
4. De-escalation: Transition to oral intake when tolerated

Antidiarrheal / Supportive Medications

Dietary Management

• Bland diet: Easily digestible, low fat, low fiber - boiled chicken/white fish + white rice
• Hydrolyzed protein diet: Food allergy / adverse food reaction
• High-fiber diet: Large bowel diarrhea, fiber-responsive diarrhea (trichuris, idiopathic colitis)
• Highly digestible / EPI diet: Enzyme supplementation (Viokase, pancreatic enzyme powder)
• Withhold food 12-24 hours (acute mild diarrhea only - do NOT fast severely ill animals)

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PART 3: DIFFERENTIATION OF KEY DISEASES

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3.1 VOMITING vs. REGURGITATION vs. RETCHING (Must Know!)

3.2 KEY DISEASE DIFFERENTIATIONS

Parvovirus vs. AHDS (Hemorrhagic Gastroenteritis)

IBD vs. Alimentary Lymphoma (Cats - Very Common Exam Topic)

EPI vs. IBD/PLE (Small Bowel Malabsorption)

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PART 4: PATHOGNOMONIC SIGNS

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PART 5: IMPORTANT EXAM / INTERVIEW / CLIENT QUESTIONS

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Q1. What is the most common cause of acute vomiting and diarrhea in adult dogs?

Q2. What is the most dangerous cause of acute vomiting and diarrhea in puppies?

Q3. How do you differentiate small bowel from large bowel diarrhea?

Q4. What is the Na:K ratio and what does a low ratio mean?

Q5. What antiemetic is the gold standard in small animal veterinary medicine?

Q6. Why should you NOT use metoclopramide in suspected GI obstruction?

Q7. What is the pathognomonic CBC finding in canine parvovirus?

Q8. What is AHDS and how is it different from parvovirus?

Q9. What is the diagnostic test for Exocrine Pancreatic Insufficiency (EPI)?

Q10. What is a linear foreign body and why is it dangerous in cats?

Q11. What is PLE and what are its hallmarks?

Q12. What emetic do you use in dogs vs. cats?

• Dogs: Apomorphine (D2 agonist; given subconjunctivally or IV; fast acting)
• Cats: Xylazine (alpha-2 agonist; IM or SQ; also causes sedation)
• Alternative (both): 3% hydrogen peroxide (dogs only - irritant; not in cats - toxic!)

Q13. When is vomiting induction CONTRAINDICATED?

• Caustic/corrosive ingestion (acids, alkalis) - re-exposure burns esophagus
• Petroleum products
• Already unconscious or seizuring patient
• Respiratory compromise
• Foreign body that could cause more trauma on the way back up
• More than 2-4 hours after ingestion (already absorbed)

Q14. How do you treat GDV (Gastric Dilatation-Volvulus)?

1. Stabilize first - IV fluids, oxygen, pain relief, treat shock
2. Decompress stomach - pass orogastric tube OR trocharize (needle through flank)
3. Surgical correction - detort stomach + gastropexy (to prevent recurrence)
4. Monitor for cardiac arrhythmias (ventricular premature contractions - common post-GDV)

Q15. What are the 4 mechanisms of diarrhea?

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PART 6: QUICK SUMMARY FLOWCHART

VOMITING / DIARRHEA PATIENT
          |
    ┌─────┴─────┐
Is it VOMITING    Is it DIARRHEA
or REGURGITATION? Small vs. Large Bowel?
          |              |
   [History + PE]   [Character of stool]
          |
   Acute (< 7 days) → Dietary? Infectious? Toxin? Obstruction?
   Chronic (> 7 days) → IBD? Neoplasia? EPI? Systemic disease?
          |
   [MINIMUM DATABASE: CBC, CHEM, UA, FECAL]
          |
   ┌──────────────┐
   Parvo test?       Na:K ratio?     Ultrasound?
   PCV/TP?           TLI?            Radiographs?
          |
   [TREATMENT: Fluids, Antiemetics, Antibiotics if indicated,
    Bland diet, Treat underlying cause]

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REFERENCES & SOURCES

• Guyton & Hall Textbook of Medical Physiology (physiology of vomiting/diarrhea, mechanisms)
• Sleisenger & Fordtran's Gastrointestinal and Liver Disease (GI pathophysiology)
• Ngwenyama TT. "Fluid and Electrolyte Therapy in the Patient with Vomiting and Diarrhea." Vet Clin North Am Small Anim Pract. 2026 [PMID: 41162294]
• Mazzaferro EM. "Update on Canine Parvoviral Enteritis." Vet Clin North Am Small Anim Pract. 2025 [PMID: 40044515]
• Dupont N, et al. "Retrospective study of 237 dogs with AHDS." J Vet Intern Med. 2021 [PMID: 33638574]
• Today's Veterinary Practice: "Approach to Diagnosis and Therapy of the Patient with Acute Diarrhea" (2013)
• Washington State University Veterinary Teaching Hospital - Diarrhea in Dogs and Cats

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1. Vomiting ki complete neurology - CTZ, vagal afferents, vomiting center
2. Diarrhea ke 4 mechanisms - osmotic, secretory, permeability, motility
3. Small vs. large bowel diarrhea differentiation (exam mein zaroor aata hai)
4. Key diseases ki differentiation - parvovirus vs. AHDS, IBD vs. lymphoma, EPI vs. PLE
5. Pathognomonic signs jo seedha diagnosis batate hain
6. Treatment protocols - antiemetics, fluid therapy, dietary management
7. Interview/exam questions with complete answers

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🐾 VETERINARY MASTERCLASS GUIDE

REGURGITATION + PANCREATITIS + LIVER DISEASE

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SECTION 1: REGURGITATION

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1.1 DEFINITION

Key concept to remember: Regurgitation is an ESOPHAGEAL problem. Vomiting is a GASTRIC problem. This is the most fundamental distinction in veterinary gastroenterology.

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1.2 VOMITING vs. REGURGITATION - MASTER TABLE

Pathognomonic clue:

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1.3 ANATOMY - WHY REGURGITATION HAPPENS

• Upper Esophageal Sphincter (UES): At pharyngo-esophageal junction; striated muscle; prevents air entry
• Lower Esophageal Sphincter (LES) / Cardia: At gastroesophageal junction; prevents gastric reflux

• Dogs: Entirely STRIATED (voluntary) muscle throughout the whole esophagus
• Cats: Striated in upper 2/3, smooth muscle in lower 1/3

1. Coordinated peristalsis (primary and secondary waves)
2. Intact vagal innervation (CN X)
3. Normal neuromuscular junction (acetylcholine release)
4. Normal smooth/striated muscle function

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1.4 CAUSES OF REGURGITATION

ESOPHAGEAL CAUSES (Primary)

• Megaesophagus = generalized dilation and loss of peristalsis of the entire esophagus
• Food accumulates and cannot move to the stomach - it sits, ferments, and is regurgitated
• Can be congenital (present at birth) or acquired (develops later in life)

• Seen in puppies when weaning begins (~ 3 months of age)
• Pathophysiology: defect in vagal afferent innervation or esophageal muscle abnormality
• Predisposed breeds: Wire Fox Terrier (autosomal recessive), Miniature Schnauzer (autosomal dominant/recessive), Great Dane, German Shepherd, Labrador Retriever, Newfoundland, Irish Setter, Chinese Shar-Pei

• Foreign bodies (bones most common in dogs; sewing needles in cats)
• Esophageal stricture (post-esophagitis scarring; post-vomiting; pill esophagitis from doxycycline in cats!)
• Esophageal neoplasia (squamous cell carcinoma, leiomyoma, GIST)
• Extraluminal compression (lymph nodes, mediastinal masses, lung tumors)

• Developmental anomaly where the aortic arch forms on the RIGHT instead of left
• Creates a fibrous ring that encircles and compresses the esophagus at the heart base
• Classic presentation: puppy/kitten that regurgitates when starting solid food (weaning age)
• Diagnosis: Radiography (dilation of esophagus CRANIAL to heart base)
• Treatment: SURGICAL LIGATION and cutting of the ligamentum arteriosum
• Pathognomonic: Regurgitation in young animal + esophageal dilation cranial to heart on X-ray

• Causes: Gastroesophageal reflux (GERD), anesthesia (acid reflux during GA), vomiting, foreign bodies, doxycycline capsules (cats - pill burns), feeding tubes
• Signs: Regurgitation, hypersalivation, odynophagia (painful swallowing), repeated swallowing
• Can progress to esophageal stricture if chronic

• Stomach acid refluxes into esophagus (especially during anesthesia - animals positioned in Trendelenburg/head-down)
• Causes esophagitis, pain, regurgitation

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1.5 CLINICAL SIGNS

• Regurgitation (hallmark sign) - passive, tubular food
• Dysphagia (difficulty swallowing) - repeated swallowing attempts
• Odynophagia - painful swallowing (esophagitis)
• Hypersalivation / ptyalism (drooling)
• Halitosis (bad breath from fermented food in esophagus)
• Weight loss / failure to thrive (food never reaches stomach)
• Aspiration pneumonia - MOST DANGEROUS COMPLICATION
  • Regurgitated material enters airway
  • Signs: cough, dyspnea, fever, nasal discharge, crackles on auscultation
  • Cranioventral lung lobe consolidation on X-ray
  • Can be FATAL

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1.6 DIAGNOSTICS

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1.7 TREATMENT

Underlying Cause Treatment (MOST IMPORTANT)

• Myasthenia Gravis: Pyridostigmine (AChE inhibitor) - prolongs ACh action at NMJ; ± immunosuppression (prednisolone)
• Hypothyroidism: Levothyroxine (L-thyroxine) supplementation
• Addison's disease: Fludrocortisone (mineralocorticoid) + prednisolone
• PRAA: Surgical ligation of ligamentum arteriosum
• Foreign body: Endoscopic retrieval or surgery
• Esophageal stricture: Balloon dilation (endoscopic)
• Esophagitis: PPIs (omeprazole), sucralfate, feeding management

Supportive Management for Megaesophagus

• "Bailey Chair" feeding: Feed the dog in an UPRIGHT position (45-90 degrees, like a human) so gravity helps food fall into the stomach; dog must remain upright for 15-30 minutes after eating
• Multiple small meals daily - easier to swallow in smaller amounts
• Food texture modification - some dogs do better with liquids (water + kibble slurry), others with solid food (trial and error)
• Elevated food bowl - less beneficial than upright positioning
• Nasogastric (NG) or esophagostomy tube - if severe malnutrition
• Sildenafil (phosphodiesterase-5 inhibitor) - one study showed some improvement in LES relaxation and esophageal function; experimental
• Aspiration pneumonia treatment: Antibiotics (broad-spectrum), oxygen, nebulization

Prognosis

• Congenital megaesophagus: Variable - some puppies improve as the nervous system matures; others have lifelong disease
• Secondary megaesophagus (MG, Addison's, hypothyroid): GOOD if underlying disease is treated early
• Idiopathic megaesophagus: POOR prognosis; aspiration pneumonia is major mortality cause (VCA Animal Hospitals)

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SECTION 2: PANCREATITIS

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2.1 DEFINITION

• Acute Pancreatitis = Reversible inflammatory episode; function can return to normal if cause is removed
• Chronic Pancreatitis = Repeated episodes; causes irreversible destruction of exocrine pancreas; leads to fibrosis and loss of acinar cells

"Acute pancreatitis is caused by autodigestion of the pancreas by intraacinara (within acinar cells) activation of pancreatic enzymes." - Robbins & Kumar Basic Pathology

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2.2 NORMAL PANCREATIC PHYSIOLOGY (Review)

1. Exocrine function (acinar cells - 80% of pancreas): Produce digestive enzymes (amylase, lipase, trypsin, chymotrypsin, elastase, phospholipase) as INACTIVE PROENZYMES (zymogens) to prevent self-digestion
2. Endocrine function (islets of Langerhans - 20%): Produce insulin (beta cells), glucagon (alpha cells), somatostatin (delta cells)

The Safety Mechanism That Prevents Autodigestion:

• Enzymes are stored as INACTIVE zymogens in secretory granules
• They are only activated in the DUODENUM by enteropeptidase (enterokinase), which converts trypsinogen → TRYPSIN
• Trypsin then activates ALL other proenzymes
• Intracellular trypsin inhibitors (PSTI/SPINK1) neutralize any accidentally activated trypsin

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2.3 PATHOPHYSIOLOGY OF PANCREATITIS

THREE PATHWAYS OF INITIATION (Robbins & Kumar):

• Gallstone or biliary sludge blocks the common bile duct / ampulla of Vater
• Intraductal pressure rises → enzyme-rich interstitial fluid accumulates
• Lipase (already active) causes local fat necrosis
• Inflammatory cytokines released → edema, impaired blood flow → ischemia → acinar cell injury

• Direct damage to acinar cells by:
  • High-fat diet / dietary indiscretion (most common in dogs)
  • Hypertriglyceridemia (Miniature Schnauzer predisposition!)
  • Ischemia
  • Drugs (azathioprine, bromides, potassium bromide, L-asparaginase, sulfonamides, zinc, tetracyclines)
  • Toxins
  • Trauma
• Injured cells release proenzymes → intracellular activation

• Normally, digestive enzymes and lysosomal hydrolases travel in SEPARATE pathways
• When packaging goes wrong (metabolic injury), they merge → proenzymes activate inside lysosomes → lysosomal rupture → enzyme release

Cascade of Damage Once Trypsin Activates:

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2.4 CAUSES OF PANCREATITIS IN DOGS AND CATS

IN DOGS:

IN CATS: (Different and important!)

"FELINE TRIADITIS" (Unique to Cats!)

The simultaneous presence of:

1. Pancreatitis
2. Inflammatory Bowel Disease (IBD)
3. Cholangitis (liver/bile duct inflammation)

Because in cats, the bile duct and pancreatic duct share a COMMON OPENING into the duodenum (unlike dogs where they open separately). So infection/inflammation can spread between all three organs easily. Armstrong & Williams, Top Companion Anim Med, 2012 [PMID: 23148855]

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2.5 CLINICAL SIGNS

In Dogs (more classic presentation):

• Vomiting - common, often the presenting complaint
• Abdominal pain - dog adopts "prayer position" (front legs down, hindquarters up) to relieve abdominal discomfort - this is nearly PATHOGNOMONIC!
• Anorexia / inappetence
• Lethargy, depression
• Diarrhea (less consistent)
• Fever
• Dehydration
• Cranial abdominal pain on palpation
• Severe cases: jaundice (biliary obstruction), ascites, respiratory distress (ARDS), collapse (shock)

In Cats (MUCH more subtle - that's why it's frequently missed!):

• Anorexia (most common sign - 87%)
• Lethargy
• Dehydration
• Hypothermia (unusual - cats can be COLD, not hot!)
• Vomiting (less common than dogs - only ~50%)
• Abdominal pain (often absent or hard to detect)
• Jaundice (from concurrent cholangitis)
• Weight loss

"Few of the diagnostic tests of value in the dog were helpful in cats." - Armstrong & Williams (2012)

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2.6 DIAGNOSTICS

Blood Tests:

Imaging:

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2.7 TREATMENT

1. Rest the pancreas (NPO initially)
2. Correct fluid and electrolyte deficits
3. Control pain and vomiting
4. Prevent complications

Step-by-Step Treatment Protocol:

• Correct dehydration and hypovolemia
• Lactated Ringer's Solution (LRS) or Plasma-Lyte as first choice
• Add KCl if hypokalemia present
• Avoid overhydration (can worsen pancreatic edema)

• Pancreatitis is VERY PAINFUL
• Buprenorphine (partial opioid agonist) - excellent for moderate pain
• Fentanyl CRI (constant rate infusion) - for severe pain
• Maropitant (Cerenia) - also has visceral analgesic properties; useful concurrently
• Avoid NSAIDs (worsen renal perfusion and GI issues)

• Maropitant (Cerenia) - first-line; NK1 antagonist
• Metoclopramide CRI - prokinetic, helps gastric emptying; also antiemetic
• Ondansetron - for severe/refractory vomiting

• Old teaching: "NPO for 24-48 hours to rest the pancreas"
• New evidence: Early enteral feeding (naso-esophageal or naso-gastric tube) IMPROVES outcomes; reduces bacterial translocation; supports gut integrity; prevents muscle wasting
• Begin small amounts of low-fat, highly digestible diet ASAP
• Cats: MUST be fed early to prevent hepatic lipidosis!
• If can't eat voluntarily: nasogastric tube or esophagostomy tube placement

• NOT routinely recommended (pancreatitis is mostly sterile initially)
• Use only if evidence of infection: fever, positive blood cultures, sepsis, aspiration pneumonia
• If needed: ampicillin/sulbactam, metronidazole, or enrofloxacin

• Gastroprotectants: Omeprazole (PPIs) if vomiting, gastric ulceration risk
• Plasma transfusion: Provides alpha-macroglobulins that neutralize proteases; used in severe cases
• Dopamine: Low-dose to maintain splanchnic blood flow (controversial)
• Surgery: For pancreatic abscess, pseudocyst, necrosis debridement

• DIC: Fresh frozen plasma, heparin (controversial)
• Hypocalcemia: Slow IV calcium gluconate supplementation
• Hyperglycemia/DKA: Insulin therapy
• ARDS: Oxygen therapy, mechanical ventilation
• Hepatic lipidosis (cats): Aggressive enteral nutrition

• Low-fat diet PERMANENTLY
• Omega-3 fatty acid supplementation
• Cobalamin (B12) supplementation if deficient (common with EPI)
• If leads to EPI: Pancreatic enzyme supplementation
• If leads to diabetes mellitus: Insulin therapy
• Cats with chronic pancreatitis: Often benefit from prednisolone (has anti-inflammatory effect in cats)

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2.8 COMPLICATIONS

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2.9 PANCREATITIS EXAM QUESTIONS

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SECTION 3: LIVER DISEASE (HEPATIC DISEASE)

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3.1 OVERVIEW OF LIVER FUNCTION

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3.2 CLINICAL SIGNS OF LIVER DISEASE

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3.3 HEPATIC ENCEPHALOPATHY (HE) - Key Topic

• Gut bacteria (especially urease-producing bacteria) convert protein → ammonia (NH3)
• Normally: portal blood carries ammonia to liver → converted to urea (urea cycle) → excreted by kidneys
• In liver failure or PSS: ammonia bypasses or overwhelms the liver → reaches the brain
• Ammonia → enters astrocytes (brain support cells) → converted to glutamine → astrocyte SWELLING → cerebral edema → neurological signs

• Manganese (deposited in basal ganglia)
• Endogenous benzodiazepines (GABA-A receptor agonists → sedation)
• Mercaptans (sulfur compounds from gut bacteria)
• Aromatic amino acids

• Head pressing against walls
• Aimless wandering / circling
• Ataxia (stumbling, wobbling)
• Blindness (cortical)
• Behavioral changes (aggression, confusion, depression)
• Hypersalivation
• Seizures (terminal sign)
• Signs often EPISODIC and worsen after protein-rich meals

• Lactulose: Laxative disaccharide that:
  1. Traps ammonia in the colon (acidifies colon → NH3 + H+ → NH4+ which cannot be absorbed)
  2. Speeds intestinal transit (flushes ammonia out)
  3. Reduces ammonia-producing bacteria
• Antibiotics (metronidazole, neomycin, rifaximin): Reduce gut bacteria that produce ammonia
• Dietary protein modification: Use HIGH-QUALITY, digestible protein (soy protein or dairy protein in dogs - soy-based diet shown beneficial); severe protein restriction is NO LONGER recommended (causes muscle wasting → more endogenous ammonia from muscle breakdown)
• Lactulose enemas: For acute HE crisis
• Treat precipitating factors: GI bleeding (blood = protein load), infection, constipation, azotemia

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3.4 MAJOR LIVER DISEASES BY SPECIES

A. CANINE LIVER DISEASES

• Progressive inflammatory disease → hepatocellular necrosis + fibrosis → eventually cirrhosis
• Causes:
  • Copper accumulation (most important recognized cause!)
  • Infectious: Leptospira interrogans (highly zoonotic!), Adenovirus type 1 (CAV-1 - Canine Infectious Hepatitis)
  • Drugs: Phenobarbital, carprofen, trimethoprim-sulfonamide
  • Idiopathic (most common after copper ruled out) - Bexfield (2017) [PMID: 28063746]
• COPPER-ASSOCIATED HEPATITIS - VERY IMPORTANT:
  • Copper normally excreted in bile; defective biliary excretion leads to hepatic accumulation
  • Bedlington Terrier - autosomal recessive mutation in COMMD1 gene → classic breed; most severe copper accumulation
  • Other predisposed breeds: Labrador Retriever, Doberman Pinscher, Dalmatian, Skye Terrier, West Highland White Terrier
  • Copper is hepatotoxic (oxidative damage) → inflammation → fibrosis → cirrhosis
  • Diagnosis: Liver biopsy with Rhodanine stain (copper stain - shows orange-red granules in hepatocytes) + quantitative copper measurement (> 2000 µg/g DW = toxic)
  • Treatment: D-penicillamine (chelates and promotes urinary excretion of copper), low-copper diet, zinc supplementation (induces metallothionein in gut, blocks copper absorption)
• Histologic criteria for CH (WSAVA Liver Standardization Group):
  • Hepatocellular apoptosis OR necrosis
  • Mononuclear or mixed inflammatory cell infiltrate
  • Regeneration
  • Fibrosis

• Hepatocytes become swollen with glycogen or fat vacuoles
• Associated with hyperadrenocorticism (Cushing's), chronic steroid use (iatrogenic Cushing's), stress
• ALP markedly elevated (often > 1000 IU/L!) while ALT is mildly elevated
• Typically benign unless underlying Cushing's is severe
• Diagnosis: Biopsy (pale vacuolated hepatocytes), low-dose dexamethasone suppression test for Cushing's

• Abnormal vessel that connects the portal circulation DIRECTLY to the systemic circulation, BYPASSING the liver
• Portal blood (full of ammonia and gut-absorbed toxins) goes straight to brain = hepatic encephalopathy
• Congenital PSS (single shunting vessel):
  • Small breeds: Yorkshire Terrier, Maltese, Shih Tzu, Miniature Schnauzer - extrahepatic shunt (outside liver)
  • Large breeds: Irish Wolfhound, German Shepherd - intrahepatic shunt (inside liver - ductus venosus fails to close)
• Acquired PSS (multiple small vessels): Develop due to chronic portal hypertension (cirrhosis)
• Classic presentation of PSS:
  • Young animal (< 2 years for congenital)
  • Small stature / failure to thrive despite eating well
  • Post-prandial (after eating) neurological signs
  • Urinary signs (ammonium biurate crystals, urolithiasis)
  • Hepatic encephalopathy signs
• Diagnosis:
  • Pre- and post-prandial bile acids - most useful screening test; very elevated (> 25 µmol/L fasted, > 50 µmol/L post-prandial)
  • Ammonia tolerance test (risky - can precipitate HE!)
  • Ultrasound: Abnormal vessel, small liver (microhepatia), diminished portal vasculature
  • Scintigraphy (nuclear scan): > 15% of portal blood going direct to systemic = significant shunting
  • CT angiography (best for surgical planning)
  • Ammonium biurate crystals in urine sediment
• Treatment:
  • Surgical (definitive): Ameroid constrictor or cellophane banding to gradually occlude the shunting vessel; allows portal blood to gradually readjust; preferred for extrahepatic shunts
  • Medical management: For poor surgical candidates, pre-surgical stabilization; lactulose + antibiotics + dietary management
  • Prognosis: GOOD with successful surgery (especially extrahepatic shunts - 85%+ long-term success)

• Unique to dogs - not reported in cats
• Accumulation of abnormally viscous bile within the gallbladder, forming a star-shaped or kiwi-shaped mucocele
• Associated with Shetland Sheepdog, Cocker Spaniel, Miniature Schnauzer, hypothyroidism, hyperadrenocorticism, dyslipidemia
• Signs: Vomiting, anorexia, jaundice, abdominal pain; can rupture → bile peritonitis (EMERGENCY!)
• Diagnosis: Ultrasound - "kiwi fruit" or "stellate" (star-shaped) pattern in gallbladder
• Treatment: Cholecystectomy (surgical gallbladder removal) before rupture; medical with ursodeoxycholic acid in stable cases
• Pathognomonic: "Kiwi fruit" sign on ultrasound

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B. FELINE LIVER DISEASES

This is arguably the most important feline liver disease to know completely.

• Cats have UNIQUE metabolic vulnerability: obligate carnivores; high protein metabolism; low capacity for hepatic lipid oxidation
• When a cat STOPS EATING (anorexia from ANY cause) for even 2-5 days:
  • Body fat stores are mobilized → triglycerides flood the bloodstream
  • Liver is overwhelmed → cannot process all the fat → fat ACCUMULATES in hepatocytes
  • Hepatocytes become bloated with fat → cannot function → cholestasis → jaundice → liver failure
  • This is the only disease where being OBESE makes you MORE vulnerable (obese cats have more fat to mobilize!)

• Any cause of anorexia in a cat: stress, pain, other illness (pancreatitis, IBD, renal disease), travel, change in environment, new pet in house
• Obesity is the #1 risk factor
• Concurrent pancreatitis very common

• Jaundice (icterus) - hallmark
• Anorexia (the cause AND the perpetuating factor)
• Vomiting
• Lethargy, depression
• Weight loss
• Hepatomegaly (enlarged liver)
• Neurological signs if HE develops
• Drooling, nausea
• Muscle wasting (hepatic failure)

• History of anorexia (2+ days in obese cat)
• Blood tests: Markedly elevated ALP (very high ALP in a CAT is SIGNIFICANT - unlike dogs, cats have low baseline ALP); elevated ALT; hyperbilirubinemia; hypokalemia; hypomagnesemia
• Ultrasound: Hyperechoic (bright white) liver - fat makes liver echogenic; hepatomegaly
• FNA (Fine Needle Aspirate) of liver - DIAGNOSTIC: shows hepatocytes stuffed with lipid vacuoles (lipid vacuolation); simple and safe to perform with ultrasound guidance
• Rule out underlying cause (blood glucose, T4, urinalysis, thoracic X-ray)

• Feeding tube placement is the cornerstone of treatment! Cat must receive adequate calories
  • Esophagostomy tube (E-tube): Preferred; easy to place, can go home with tube
  • PEG tube (Percutaneous Endoscopic Gastrostomy): For longer-term use
  • Nasogastric (NG) tube: Short-term
• Feed HIGH-PROTEIN, MODERATE-FAT diet through tube (protein stimulates lipid oxidation in cats)
• Do NOT restrict protein (despite liver disease - cats NEED protein to reverse HL)
• Supplement: Cobalamin (B12), thiamine (B1), potassium, magnesium
• IV fluids for dehydration
• Antiemetics for nausea (maropitant)
• S-Adenosylmethionine (SAMe): Antioxidant, hepatoprotectant; supports glutathione synthesis
• Vitamin E: Antioxidant
• Carnitine: Helps fat oxidation in liver
• Treat underlying cause simultaneously

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• Most common form of chronic inflammatory liver disease in cats
• Inflammation of the bile ducts (cholangitis) ± liver (cholangiohepatitis)
• THREE FORMS (important for differential diagnosis):

• Signs: Jaundice, vomiting, anorexia, weight loss, hepatomegaly, fever (neutrophilic form), abdominal pain
• Diagnosis: Chemistry (elevated ALP, ALT, GGT, bilirubin), ultrasound (thickened bile ducts, echogenic liver), liver biopsy is DEFINITIVE (tissue diagnosis essential to determine type)
• Part of Feline Triaditis with pancreatitis + IBD

• Lymphoma = most common hepatic tumor in cats (unlike dogs where hepatocellular carcinoma is #1)
• Also: bile duct carcinoma (cholangiocarcinoma), mast cell tumor, hepatocellular carcinoma

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3.5 DIAGNOSTICS FOR LIVER DISEASE (General)

Blood Biomarkers:

Imaging:

• Radiographs: Liver size and position; hepatomegaly vs. microhepatia; calcification (rare)
• Ultrasound: Parenchymal texture, echogenicity, vessel anatomy, bile duct thickness, mass lesions, ascites, PSS vessel
• Scintigraphy: Portal blood flow quantification (PSS diagnosis)
• CT angiography: Best for PSS surgical planning

Biopsy - DEFINITIVE DIAGNOSIS:

• Required to definitively diagnose type of liver disease
• Methods: Ultrasound-guided tru-cut biopsy, keyhole (laparoscopic), or exploratory laparotomy
• ALWAYS check coagulation times BEFORE biopsy (liver disease = coagulopathy = bleeding risk!)
• FNA (fine needle aspirate): Quick, minimal bleeding risk; can diagnose HL, neoplasia, but CANNOT assess architecture (can't diagnose hepatitis/fibrosis from FNA alone)

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3.6 TREATMENT OF LIVER DISEASE (General Principles)

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3.7 LIVER DISEASE COMPLICATIONS SUMMARY (Lidbury, Vet Clin North Am, 2025 [PMID: 40379581])

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3.8 EXAM / INTERVIEW QUESTIONS - LIVER DISEASE

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MASTER DIFFERENTIATION TABLE - All 3 Topics + Vomiting & Diarrhea

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REFERENCES

• Robbins & Kumar Basic Pathology - Pancreatitis pathophysiology (pages 640-641)
• Guyton & Hall Textbook of Medical Physiology - Vomiting center, GI physiology
• Armstrong PJ, Williams DA. "Pancreatitis in cats." Top Companion Anim Med. 2012 [PMID: 23148855]
• Lidbury JA, Cook AK, Steiner JM. "Hepatic encephalopathy in dogs and cats." J Vet Emerg Crit Care. 2016 [PMID: 27060899]
• Lidbury JA. "Complications of Liver Disease." Vet Clin North Am Small Anim Pract. 2025 [PMID: 40379581]
• Bexfield N. "Canine Idiopathic Chronic Hepatitis." Vet Clin North Am Small Anim Pract. 2017 [PMID: 28063746]
• DVM360: Diagnosis and Management of Megaesophagus in Dogs
• VCA Animal Hospitals: Megaesophagus
• Cornell University College of Veterinary Medicine: Liver Disorders

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Quick Summary - Kya Cover Kiya Gaya:

REGURGITATION:

• Vomiting vs. Regurgitation ka complete master table (exam mein zaroor aata hai)
• Esophageal anatomy (dogs = fully striated muscle = why MG causes megaesophagus)
• Megaesophagus - congenital + acquired causes (MG #1 cause!)
• PRAA (Persistent Right Aortic Arch) - pathognomonic for weaning-age puppies
• Bailey Chair feeding technique
• Pyridostigmine for Myasthenia Gravis

PANCREATITIS:

• Autodigestion mechanism - complete trypsin cascade
• Three pathways: Duct obstruction, Acinar cell injury, Defective intracellular transport
• Pancreatitis diagram image from Robbins & Kumar
• Prayer position in dogs = pathognomonic
• Feline Triaditis (Pancreatitis + IBD + Cholangitis)
• Miniature Schnauzer predisposition (hypertriglyceridemia)
• cPLI = gold standard diagnostic test
• Hypocalcemia = serious prognostic indicator
• Complications (EPI, DM, pseudocyst, DIC, ARDS)

LIVER DISEASE:

• Complete liver function overview
• Hepatic Encephalopathy - ammonia pathway, management (lactulose, metronidazole)
• Copper-associated hepatitis (Bedlington Terrier = COMMD1 gene)
• PSS (Portosystemic Shunt) - ammonium biurate crystals, bile acids
• Gallbladder Mucocele - "kiwi fruit" ultrasound sign
• Feline Hepatic Lipidosis - MOST IMPORTANT feline liver disease; esophagostomy tube = treatment
• Feline Cholangitis - 3 types + treatment
• Why ALP is more significant in cats than dogs
• Why protein restriction is no longer recommended in HE

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🐾 VETERINARY OPHTHALMOLOGY MASTERCLASS

CORNEAL ULCERS + KCS + ANTERIOR UVEITIS

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SECTION 1: CORNEAL ULCERS (ULCERATIVE KERATITIS)

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1.1 ANATOMY OF THE CORNEA - UNDERSTAND FIRST

OUTSIDE (Tear Film)
    ↓
1. Epithelium (5-7 cell layers thick - MOST SENSITIVE; contains pain receptors)
2. Bowman's Layer (acellular basement membrane - thin)
3. Stroma (THICKEST layer - 90% of corneal thickness; collagen fibrils + keratocytes)
4. Descemet's Membrane (basement membrane of endothelium - thin but very TOUGH)
5. Endothelium (single cell layer; contains Na-K ATPase PUMP - keeps cornea dehydrated and clear)
    ↓
INSIDE (Anterior Chamber)

• Dog cornea thickness: 0.55 mm (center), 0.65 mm (periphery)
• Cat cornea thickness: ~0.58 mm (center and periphery similar)
• The cornea is AVASCULAR (gets oxygen from tear film and aqueous humor)
• The cornea has the HIGHEST density of sensory nerve endings of any tissue in the body - this is why corneal ulcers are EXTREMELY PAINFUL
• The superficial cornea (epithelium) is the MOST sensitive layer

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1.2 DEFINITION

• An erosion = loss of only epithelium (no stromal involvement)
• An ulcer = loss of epithelium + some degree of stromal involvement

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1.3 CLASSIFICATION BY DEPTH (Most Important System!)

GRADE 1: Superficial Ulcer (Epithelial Erosion)

• Loss of epithelium ONLY
• Stroma is exposed but NOT lost
• MOST PAINFUL paradoxically - because the superficial nerve endings are exposed
• Fluorescein stain: POSITIVE (stain pools in the defect)
• Treatment: Topical antibiotics, lubricants, ± E-collar

GRADE 2: Superficial Stromal Ulcer

• Loss of epithelium + loss of superficial stroma (< 50% stromal depth)
• Risk of bacterial colonization
• Fluorescein stain: POSITIVE

GRADE 3: Deep Stromal Ulcer

• Loss of epithelium + loss of > 50% stromal depth
• THREATENS structural integrity of the eye
• Risk of rupture if progresses
• Requires aggressive treatment and possibly surgery

GRADE 4: Descemetocele

• Loss of ALL stroma - only Descemet's membrane remains as the floor of the ulcer
• Descemet's membrane does NOT absorb fluorescein dye!
• Fluorescein stain: NEGATIVE at the very center (because no stroma remains!) but POSITIVE at the edges
• This is a SURGICAL EMERGENCY - one sneeze, one paw rub, and the eye ruptures
• Pathognomonic: Negative fluorescein staining at center of deepest ulcer = Descemetocele

GRADE 5: Ruptured Globe / Corneal Perforation

• The Descemet's membrane has also ruptured
• Aqueous humor (fluid) leaks out
• Iris may prolapse through the perforation
• Globe-threatening emergency

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1.4 SPECIAL TYPES OF CORNEAL ULCERS IN VETERINARY MEDICINE

A. INDOLENT ULCER (SCCED - Spontaneous Chronic Corneal Epithelial Defect)

• Definition: A superficial ulcer that REFUSES to heal through normal wound-healing processes despite appropriate treatment, persisting for weeks to months
• Mechanism: Abnormally weak adhesion between basal epithelial cells and their basement membrane. The epithelium is present but does NOT stick down - it slides loosely over the stroma like a carpet that won't stick to the floor
• There is also an abnormal, acellular (cell-free), hyaline zone in the anterior stroma that physically prevents epithelial adhesion
• Characteristics:
  • Superficial ONLY (does not extend into stroma)
  • Has redundant, loose, non-adherent epithelial edges ("lip" of epithelium around the ulcer)
  • Characteristic "halo" staining pattern with fluorescein - the loose epithelium uptakes dye at the edges
  • May or may not have superficial corneal vascularization (blood vessels growing in)
• Affects: Middle-aged to older dogs (average 8-9 years); any breed but Boxers are classically overrepresented
• Other predisposed breeds: Golden Retriever, Labrador, Corgi, Samoyed, Poodle
• Treatment:
  1. Debridement - Gently remove all loose epithelium with a dry cotton-tipped swab or surgical sponge (don't scrape the stroma)
  2. Grid/Punctate Keratotomy - Using a 25-gauge needle, lightly score the ulcer bed in a grid pattern to break up the acellular hyaline zone and create microchannels for new blood vessels and epithelial adhesion
  3. Diamond burr keratectomy - Mechanical superficial keratectomy (preferred over grid keratotomy by ophthalmologists); removes the abnormal anterior stroma
  4. Topical broad-spectrum antibiotic (prophylactic)
  5. E-collar (Elizabethan collar - cone) - ALWAYS
  6. Oral NSAIDs for pain
  7. If grid keratotomy fails: Superficial keratectomy (surgical removal of abnormal tissue)

B. MELTING ULCER (Stromal Lysis)

• Definition: An ulcer in which bacterial-produced and host-produced enzymes (Matrix Metalloproteinases - MMPs, particularly MMP-2 and MMP-9, and bacterial proteases and collagenases) are ACTIVELY DESTROYING the corneal stroma
• The stroma dissolves like jelly - the eye can go from a small ulcer to a perforation in HOURS
• Appearance: Grey-white, gelatinous, liquefied-looking stroma at the ulcer base. Distinguished from corneal edema by its soft, jelly-like texture
• Key causative organisms: Pseudomonas aeruginosa (most aggressive collagenase producer!), Beta-hemolytic Streptococcus, Staphylococcus
• Predisposed: Brachycephalic breeds (Pugs, Bulldogs, French Bulldogs, Shih Tzu, Pekinese) due to:
  • Exophthalmos (bulging eyes) - increased exposure
  • Lagophthalmos (incomplete eyelid closure) - incomplete corneal protection
  • Macroblepharon (large palpebral fissure)
  • Reduced corneal sensation (trigeminal nerve compression)
• Why topical steroids are CONTRAINDICATED in melting ulcers:
  • Steroids INCREASE tear protease activity
  • Steroids increase collagenase activity
  • Steroids impair corneal healing
  • Using steroids on a melting ulcer = accelerating destruction
• Treatment:
  • STOP all topical steroids immediately
  • Aggressive topical antibiotics every 1-2 hours (fluoroquinolones: ciprofloxacin 0.3%, ofloxacin)
  • Antiprotease therapy: Acetylcysteine (5-10% topical solution) - N-acetylcysteine inhibits MMPs; EDTA drops; autologous serum (from the patient's own blood) - contains natural anti-proteases (alpha-2 macroglobulin)
  • Systemic doxycycline - inhibits MMPs systemically
  • Systemic NSAIDs or oral prednisolone (to reduce inflammation - NEVER topical steroids)
  • Surgical: Conjunctival pedicle graft or corneal graft if severe

C. FELINE HERPESVIRUS (FHV-1) ULCERS

• Feline Herpesvirus Type 1 is the most common cause of corneal ulcers in CATS
• FHV-1 causes direct viral lysis of corneal epithelial cells
• Initial: Dendritic (branching, tree-shaped) ulcers - pathognomonic for herpes keratitis
• Can progress to geographic (large map-like) ulcers
• May cause corneal stromal disease in chronically infected cats
• Key feature: Often BILATERAL; associated with upper respiratory signs (sneezing, nasal discharge); can be recurrent (virus stays latent in trigeminal ganglion and reactivates with stress)
• Treatment: Topical antiviral (idoxuridine 0.1%, trifluridine 1%), oral famciclovir (100-125 mg/cat every 12 hrs - drug of choice for systemic FHV treatment), L-lysine supplementation (controversial but widely used), topical lubricants

D. CORNEAL SEQUESTRUM (Feline Specific!)

• A unique condition seen ONLY in cats (not reported in dogs)
• A dark brown to black, plaque-like focus of degenerate (dead) corneal stromal tissue that forms, usually after chronic corneal trauma or FHV infection
• Appears as a brown/black opaque plaque embedded in the cornea
• Can cause chronic discomfort, tearing, blepharospasm
• Predisposed breeds: Persian, Himalayan, Siamese, Burmese (all brachycephalic cats)
• Treatment: Superficial keratectomy (surgical removal); healing usually good but recurrence possible
• Pathognomonic: Dark brown/black corneal plaque in a brachycephalic cat = Corneal Sequestrum

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1.5 CAUSES OF CORNEAL ULCERS IN DOGS AND CATS

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1.6 CLINICAL SIGNS

• Pain - blepharospasm (squinting), pawing at the eye
• Photophobia - avoiding light (due to ciliary spasm from reflex uveitis)
• Purulent/mucoid discharge
• Protrusion of nictitating membrane (third eyelid rises to protect painful eye)
• Periocular changes - conjunctival hyperemia (redness), chemosis (swollen conjunctiva)

• Epiphora (excessive tearing/watering)
• Corneal edema (blue-white haze due to fluid entering the stroma through the damaged epithelium)
• Superficial corneal vascularization (blood vessels grow into cornea from limbus - response to chronic ulceration; superficial = pink, brush-like vessels)
• Miosis (constricted pupil) - from reflex anterior uveitis (the pain signals trigger uveitis)
• Aqueous flare (protein in anterior chamber) - from secondary uveitis

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1.7 DIAGNOSIS

Step 1: Schirmer Tear Test (STT) FIRST

• Always do STT BEFORE instilling any drops!
• Rules out KCS as the underlying cause
• Normal: > 15 mm/minute in dogs; > 10 mm/minute in cats
• If STT is low, treat KCS simultaneously

Step 2: Fluorescein Stain - THE MOST IMPORTANT TEST

• Fluorescein is a water-soluble, orange dye that is hydrophilic (water-loving)
• It is REPELLED by the intact lipid-based epithelium (normally)
• It is ATTRACTED to and pools in any area where epithelium is lost (stroma is hydrophilic = loves water = takes up dye)
• Application: Place fluorescein strip in lower conjunctival sac; flush with sterile saline; examine under cobalt blue light (dye fluoresces bright GREEN under blue light)
• Positive stain = Green fluorescence = Epithelial defect PRESENT = Ulcer confirmed
• Descemetocele: NEGATIVE at the center (no stroma to take up dye!) but POSITIVE ring at the edges
• Use cobalt blue light - routine white light examination misses subtle ulcers

Step 3: Tonometry (IOP measurement)

• Check intraocular pressure (IOP)
• Uveitis usually causes LOW IOP (ciliary body shutdown)
• If IOP is HIGH in an inflamed eye = secondary glaucoma = serious complication

Step 4: Additional Tests

• Corneal cytology: Sample from ulcer margin - look for bacteria, neutrophils, fungal hyphae
• Bacterial culture and sensitivity: From deep/infected ulcers before starting antibiotics
• Rose Bengal stain: Stains dead or devitalized epithelial cells; useful for early FHV dendritic ulcers
• Slit-lamp biomicroscopy: Detailed examination of ulcer depth, corneal layers
• Complete ocular examination: Rule out entropion, distichiasis, foreign body, ectopic cilia

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1.8 TREATMENT BY ULCER TYPE

All Corneal Ulcers - General Principles:

• Prevent/treat secondary bacterial infection
• Choices: Triple antibiotic (neomycin-polymyxin-bacitracin), tobramycin 0.3%, ofloxacin 0.3%, ciprofloxacin 0.3% (fluoroquinolones for infected/deep ulcers)
• Frequency: Every 4-6 hours for superficial; every 1-2 hours for melting ulcers
• NEVER use aminoglycosides (gentamicin, tobramycin) as SOLE treatment - Pseudomonas can be resistant

• Use when REFLEX UVEITIS is present (miosis, aqueous flare, severe photophobia)
• Mechanism: Parasympatholytic → dilates pupil (mydriasis) + paralyzes ciliary muscle (cycloplegia)
• Benefits: Relieves pain from ciliary spasm; prevents posterior synechiae (iris sticking to lens)
• Frequency: Every 8-24 hours until pupil dilated, then taper
• CONTRAINDICATED if IOP is elevated (will worsen glaucoma!)
• CONTRAINDICATED if KCS is present (decreases tear production further)
• In cats: Use atropine OINTMENT only (not drops) - drops drain to nasopharynx → extremely bitter taste → excessive salivation, frothing, vomiting

• Prevents self-trauma (pawing, rubbing)
• Most critical single instruction to give the owner!
• "If you take the cone off, the eye will get worse."

• Meloxicam or carprofen for pain
• Corneal ulcers are very painful

• Topical corticosteroids on any ulcer - impair healing, increase risk of infection, worsen melting
• Topical anesthetics (proxymetacaine, tetracaine) as dispensed medications - epitheliotoxic; delay healing; mask pain that protects the eye

Surgical Options for Deep/Non-Healing Ulcers:

• Conjunctival pedicle graft: Brings blood supply and antiproteases to the ulcer; preferred for deep/melting ulcers
• Corneoconjunctival transposition
• Corneal graft (when > 50% stromal depth lost)
• Temporary tarsorrhaphy (sewing eyelids partially together) - provides protection for healing
• Enucleation (eye removal) - for ruptured globes with no vision potential

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1.9 KEY DIFFERENTIATIONS

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SECTION 2: KERATOCONJUNCTIVITIS SICCA (KCS) - DRY EYE SYNDROME

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2.1 DEFINITION

• KCS = "Kera" (cornea) + "to" + "conjunctivitis" (conjunctival inflammation) + "Sicca" (Latin for DRY)
• Also known simply as "Dry Eye Syndrome"
• Very common in dogs (annual incidence 0.3-1.52% in North America)
• Uncommon in cats (cats have primarily lipid-deficient tear film disease instead)

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2.2 THE TEAR FILM - UNDERSTAND THOROUGHLY

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2.3 PATHOPHYSIOLOGY

1. CD4+ T-lymphocytes (helper T-cells) infiltrate the lacrimal gland tissue
2. They attack and destroy lacrimal acinar cells (the secretory cells that make aqueous tears)
3. Progressive glandular atrophy and fibrosis
4. Tear production drops → aqueous layer becomes insufficient
5. Corneal surface dries → epithelial cell death, corneal ulceration, chronic inflammation
6. Goblet cells (mucin producers) also affected → mucin becomes thick and stringy
7. Result: thick, ropy, mucopurulent (mucous + pus) discharge

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2.4 CAUSES OF KCS IN DOGS

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2.5 BREED PREDISPOSITIONS

• English Bulldog, American Cocker Spaniel - highest prevalence (up to 30% lifetime risk!)
• West Highland White Terrier
• Yorkshire Terrier (also congenital alacrima)
• Shih Tzu, Lhasa Apso, Pekingese
• Cavalier King Charles Spaniel
• Pug
• Boston Terrier
• Miniature Schnauzer
• Bloodhound

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2.6 CLINICAL SIGNS

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2.7 DIAGNOSIS

Schirmer Tear Test (STT) - THE DIAGNOSTIC TEST

1. Before ANY eye drops, without topical anesthetic
2. Fold standardized Whatman filter paper strip at notch
3. Place hooked end in LOWER conjunctival sac (not touching cornea)
4. Close eyelids gently around strip
5. Wait EXACTLY 60 seconds
6. Read wetted length in millimeters

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2.8 TREATMENT

First-Line: Immunomodulatory Therapy (Tear Stimulants)

• Calcineurin inhibitor (blocks calcineurin enzyme in T-cells)
• Blocks transcription of cytokine genes (IL-2, IL-4, IFN-gamma) in activated T-cells
• Prevents T-cell activation and proliferation
• Reduces T-cell-mediated destruction of lacrimal gland
• ALSO directly stimulates lacrimogenesis (tear production) - possibly via effects on prolactin receptors
• Isolated from fungus Tolypocladium inflatum (1976)

• 0.2% ointment (Optimmune) - twice daily (every 12 hours)
• Compounded 1-2% cyclosporine in olive/corn oil if 0.2% insufficient
• Allow 30-45 days minimum for full response
• If STT improves > 20 mm/min: can reduce to once daily for maintenance
• Lifelong treatment required (stopping causes relapse)

• 50-80% of dogs respond to 0.2% CsA
• Severely affected dogs (STT 0-5 mm/min) may respond less well
• Must evaluate after 6-8 weeks before declaring failure

• 100 times MORE POTENT than cyclosporine
• Used as 0.02%-0.03% ophthalmic solution or ointment
• Dogs that fail cyclosporine may respond to tacrolimus
• Studies show tacrolimus is as effective as cyclosporine; some suggest superior in non-responders
• Compounded in olive oil for better bioavailability

• Macrolide immunosuppressant; similar mechanism to tacrolimus
• Less commonly used in veterinary medicine

• Newer option; 0.02% aqueous topical solution
• Different mechanism (mTOR inhibition, not calcineurin)
• Has shown increased tear production in dogs

Second-Line: Tear Film Supplementation

• Methylcellulose, carbomer, hyaluronic acid (sodium hyaluronate) - based ocular lubricants
• Provide temporary relief; do NOT treat underlying cause
• Must be used frequently (every 1-4 hours) - impractical as sole treatment
• Use as ADJUNCT to immunomodulators, especially initially when tear stimulants haven't started working yet

Third-Line: Additional Medications

• SPECIFICALLY for NEUROGENIC KCS (nerve damage causing reduced lacrimation)
• Stimulates the parasympathetic receptors on lacrimal gland to secrete tears
• Oral pilocarpine: 1-2 drops of 2% solution on food, 2-3x daily
• Topical: 0.1-0.2% dilute pilocarpine ophthalmic drops
• Side effects: vomiting, diarrhea, salivation (if too high a dose)

• Break up thick, ropy mucoid discharge
• Make it easier to clear

• For secondary bacterial conjunctivitis and corneal ulceration

• Used short-term if no ulcer present - reduces conjunctival inflammation
• Prednisolone acetate 1% or dexamethasone 0.1%
• NEVER use if corneal ulcer is present

Surgical Options (Refractory Cases)

• Surgically redirect the parotid salivary gland duct to open in the conjunctival sac instead of the mouth
• Saliva then wets the eye!
• Works reasonably well but complications include:
  • Mineral deposits on cornea (calcium salts in saliva) especially when animal eats/drinks
  • Overflow when eating (food smell stimulates salivation → eye wets excessively)
  • Requires careful client education

• Slow-release CsA implant placed under conjunctiva
• Provides 18 months of tear stimulation from single procedure

• For end-stage, blind, painful eyes that cannot be managed medically

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2.9 PROGNOSIS

• Early diagnosis + lifelong cyclosporine: EXCELLENT - vision preserved, comfort maintained
• Delayed treatment: Risk of permanent corneal scarring, pigmentation, and BLINDNESS
• Neurogenic KCS (pilocarpine-responsive): Variable; depends on whether nerve damage recovers
• Drug-induced (sulfonamides): May be irreversible even after stopping the drug

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SECTION 3: ANTERIOR UVEITIS (IRIDOCYCLITIS)

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3.1 ANATOMY OF THE UVEAL TRACT

ANTERIOR UVEA:
  ├── Iris (colored ring around pupil; contains sphincter and dilator pupillae muscles)
  └── Ciliary Body (produces aqueous humor; controls lens accommodation; contains ciliary muscle)

POSTERIOR UVEA:
  └── Choroid (vascular layer between retina and sclera; nourishes retina)

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3.2 PATHOPHYSIOLOGY

1. The trigger (trauma, infection, immune activation, tumor) causes inflammation
2. Prostaglandins (PGE2), histamine, cytokines, and leukotrienes are released
3. These inflammatory mediators BREAK DOWN the Blood-Aqueous Barrier
4. Blood vessels become hyperpermeable (leaky)
5. Plasma PROTEINS leak into the anterior chamber → Aqueous Flare (cloudy, hazy aqueous)
6. White blood cells (WBCs) migrate into the anterior chamber → Aqueous Cells
7. Fibrin may leak in → Fibrin clots in anterior chamber
8. If severe: WBCs settle gravitationally → Hypopyon (white layer of cells at bottom of anterior chamber)
9. If blood vessels rupture: Hyphema (blood in anterior chamber - red)

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3.3 CLINICAL SIGNS - "THE UVEITIS SIGN GRID"

MUST KNOW: 8 Classic Signs of Anterior Uveitis

Additional Signs:

• Keratic precipitates (KPs): WBC aggregates deposited on the posterior corneal endothelium; appear as white dots on back of cornea (especially in cats)
  • Fine KPs = lymphocytes, plasma cells (chronic, immune-mediated)
  • Mutton-fat KPs (large, greasy) = macrophages + epithelioid cells (granulomatous uveitis - FIP, blastomycosis)
• Hypopyon (white cells layer at bottom of anterior chamber) - severe inflammation
• Hyphema (blood in anterior chamber) - rupture of inflamed iris vessels
• Rubeosis iridis (new blood vessels on iris surface) - chronic uveitis
• Iris color change (darker, "muddy" iris) - inflamed iris changes appearance
• Posterior synechiae (iris adheres to anterior lens capsule) - inflammatory fibrin glues iris to lens
• Iris bombe - complete 360° posterior synechiae → aqueous humor cannot flow through pupil → builds up behind iris → pushes iris forward → acute angle closure glaucoma
• Secondary glaucoma - trabecular meshwork blocked by inflammatory cells and debris

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3.4 CAUSES OF ANTERIOR UVEITIS

OCULAR (Primary / Reflex) CAUSES

SYSTEMIC (Infectious) CAUSES

IMMUNE-MEDIATED CAUSES

• Autoimmune attack against melanocytes (pigment-containing cells) in uvea AND skin
• Bilateral granulomatous panuveitis + depigmentation of skin/nose/lips/eyelids
• Most commonly affected: Akita Inu, Siberian Husky, Samoyed, Chow Chow, Shetland Sheepdog
• Treatment: Aggressive, long-term immunosuppression (prednisolone + azathioprine)
• Pathognomonic: Bilateral panuveitis + vitiligo (depigmentation) of nose/lips in an Akita = Uveodermatologic syndrome

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3.5 DIAGNOSIS

Step 1: Complete Ophthalmic Examination

• Slit-lamp biomicroscopy - gold standard for detecting flare, cells, KPs, synechiae
• Tonometry - check IOP (LOW = uveitis; HIGH = secondary glaucoma)
• Indirect ophthalmoscopy - examine retina (choroidal lesions, retinal detachment)
• Fluorescein stain - rule out concurrent corneal ulcer

Step 2: Minimum Database (Blood Work)

• CBC: Lymphocytosis (viral), thrombocytopenia (tick-borne diseases - Ehrlichia!), anemia
• Chemistry panel: BUN/creatinine (leptospirosis), liver enzymes
• Urinalysis: Proteinuria (leptospirosis, FIP)

Step 3: Disease-Specific Tests

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3.6 COMPLICATIONS OF UNTREATED/CHRONIC UVEITIS

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3.7 TREATMENT

1. Relieve pain (blepharospasm, photophobia, ciliary spasm)
2. Reduce inflammation (prevent BAB breakdown)
3. Prevent synechiae (iris-lens adhesion)
4. Prevent secondary glaucoma
5. Treat the underlying cause

Topical Therapy:

• Prednisolone acetate 1% (best penetration - lipophilic; passes through cornea efficiently) - FIRST LINE
• Dexamethasone 0.1% - alternative
• Dosing: Every 3-6 hours initially (severe); taper over weeks as inflammation resolves
• CONTRAINDICATED if corneal ulcer present (will prevent healing and worsen ulcer)

• Diclofenac 0.1%, flurbiprofen 0.03%, ketorolac 0.5%
• Use when steroids contraindicated (concurrent corneal ulcer)
• Less potent than steroids but safe with ulcers

• Mechanism:
  • Cycloplegia (paralyzes ciliary muscle) → relieves pain from ciliary spasm
  • Mydriasis (dilates pupil) → breaks early posterior synechiae; prevents new synechiae formation
  • Stabilizes blood-aqueous barrier (reduces permeability of iris vessels)
• Dosing: Every 8-24 hours; reduce to every 24-48 hours when pupil fully dilated
• Monitor IOP - if IOP rises, STOP atropine (mydriasis worsens glaucoma by crowding the drainage angle)
• Use ointment in cats - avoid bitter drops draining to pharynx (salivation, nausea)
• AVOID in KCS - reduces already deficient tear production
• AVOID in secondary glaucoma - will worsen the pressure

Systemic Therapy:

• Prednisolone 1-2 mg/kg/day orally
• Indicated for: severe anterior uveitis, posterior uveitis, panuveitis, immune-mediated causes (uveodermatologic syndrome)
• AVOID or use cautiously if systemic infectious disease suspected (leptospirosis, brucellosis, systemic fungal) - will worsen infection
• Start topical steroids even in suspected infections - protect the eye

• Meloxicam, carprofen, aspirin
• For mild-moderate uveitis, especially if systemic steroids contraindicated
• Aspirin in cats: Use with EXTREME CAUTION - toxic at high doses; low-dose only

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MASTER COMPARISON TABLE - ALL 3 DISEASES

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IMPORTANT EXAM & INTERVIEW QUESTIONS

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• 15 mm/min = Normal

• 11-14 = Borderline
• 6-10 = Mild-moderate KCS
• 0-5 = SEVERE KCS Diagnosis of KCS requires STT-I < 10 mm/min combined with compatible clinical signs.

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• Dogs: Bacterial most common: Staphylococcus pseudintermedius, Streptococcus, Pseudomonas aeruginosa (most dangerous - produces collagenase, causes melting ulcers)
• Cats: Feline Herpesvirus-1 (FHV-1) is the most common cause of corneal ulcers in cats; also bacteria (Staphylococcus, Streptococcus), Mycoplasma
• Fungal ulcers are uncommon in both species but seen in immune-suppressed patients or those on chronic topical steroids

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REFERENCES

• Tintinalli's Emergency Medicine - Corneal Ulcer section
• Kanski's Clinical Ophthalmology 10th Edition - KCS, Anterior Uveitis
• Merck Veterinary Manual - Anterior Uveitis in Small Animals; KCS; Equine Recurrent Uveitis
• Today's Veterinary Practice - "When Is It Indolent? Diagnosis and Treatment of Indolent Corneal Ulcers" (2023)
• University of Florida Small Animal Hospital - Corneal Ulceration handout
• PMC: "Immune-mediated KCS in dogs: current perspectives on management" [PMC6067592]
• PMC: "Tacrolimus vs Cyclosporine in KCS dogs" [PMC3103853]
• MedVet - Uveitis in Dogs and Cats
• Today's Veterinary Practice - "Managing Uveitis in Dogs and Cats"
• Vettimes - "Corneal Ulcers Update in Canine and Feline Pets" (2023)
• Belknap EB. "Corneal Emergencies." Top Companion Anim Med. 2015 [PMID: 26494498]Yeh complete masterclass guide hai! Quick summary of what's covered:

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✅ Coverage Summary

🔵 CORNEAL ULCERS:

• 5 layers of cornea explained with diagram
• 4 grades by depth - Superficial → Stromal → Descemetocele → Perforation
• Special types: SCCED/Indolent (Boxer Ulcer), Melting Ulcer (Pseudomonas!), FHV-1 Dendritic Ulcers (cats), Corneal Sequestrum (cats only - black plaque)
• Fluorescein stain - how it works, why Descemetocele is NEGATIVE center
• Why NEVER give topical anesthetics home
• Brachycephalic breed predisposition
• Treatment: antibiotics, atropine, E-collar, anti-proteases for melting

🟡 KCS (DRY EYE):

• 3-layer tear film explained
• Immune-mediated T-cell destruction of lacrimal gland = main cause
• Schirmer Tear Test - values, technique, normal vs. abnormal
• Cyclosporine A (Optimmune) - mechanism (calcineurin inhibitor), dosing, brand name
• Tacrolimus - 100x more potent than CsA
• Breed predispositions (Cocker Spaniel, Bulldog)
• Sulfonamide drugs as a cause
• Parotid duct transposition surgery

🔴 ANTERIOR UVEITIS:

• Uveal tract anatomy (iris + ciliary body + choroid)
• Blood-Aqueous Barrier breakdown = core pathophysiology
• 8 classic signs including MIOSIS + LOW IOP + AQUEOUS FLARE
• KPs (Keratic Precipitates) - fine vs. mutton-fat
• Causes in dogs (Leptospira, Brucella, tick-borne) vs. cats (FIP, FeLV, FIV, Toxoplasma)
• Uveodermatologic Syndrome (Akita + vitiligo = pathognomonic)
• Lens-Induced Uveitis (cataracts leak protein)
• Treatment: prednisolone acetate 1% + atropine (ointment in cats!)
• Complications: Synechiae → Iris Bombe → Glaucoma → Phthisis Bulbi

CKD study map

1. Core concepts and renal physiology
   What CKD means, nephron loss, glomerular filtration rate (GFR), azotemia, uremia, and why CKD is progressive.
2. Causes and risk factors in dogs and cats
   Congenital disease, chronic interstitial nephritis, pyelonephritis, glomerular disease, toxins, hypertension, breed risks, and age-related disease.
3. Clinical signs and pathophysiology
   Polyuria-polydipsia (PU/PD), weight loss, dehydration, vomiting, anemia, hypertension, proteinuria, metabolic acidosis, hyperphosphatemia, hypokalemia, and uremic oral ulcers.
4. Diagnostic approach and differentials
   Urinalysis, urine specific gravity, SDMA, creatinine, UPC ratio, blood pressure, ultrasound, culture, and differentiation from acute kidney injury, pre-renal azotemia, post-renal obstruction, diabetes, and hyperthyroidism.
5. IRIS staging and substaging
   How to stage stable CKD using creatinine or SDMA, then substage by proteinuria and systemic blood pressure.
6. Treatment plan by problem
   Renal diet, hydration, antiemetics, phosphate binders, potassium, antihypertensives, antiproteinuric drugs, anemia management, acid-base correction, and treatment of urinary infection.
7. Species-specific CKD
   Important differences between dogs and cats, including feline hypokalemia and hypertension, and canine protein-losing nephropathy.
8. Monitoring, prognosis, client communication, and cases
   Recheck plans, quality-of-life assessment, emergency red flags, practical client advice, and exam/interview questions.

High-level overview

1. Core concepts and pathophysiology
2. Diagnosis, differentials, and IRIS staging
3. Treatment by problem, including carefully checked dose ranges
4. Dog versus cat CKD differences
5. Monitoring, prognosis, clinical cases, and exam questions