Vomiting

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vomiting causes etiology pathophysiology

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nausea vomiting clinical assessment diagnosis management treatment

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Vomiting

Pathophysiology

Vomiting is a coordinated reflex triggered by stimulation at four main sites (Harrison's, p. 456):

Site	Key Receptors
GI tract	Mechanoreceptors, chemoreceptors, 5-HT₃ receptors
Vestibular system	Histamine (H₁), acetylcholine receptors
Chemoreceptor trigger zone (CTZ)	Dopamine D₂, 5-HT₃, chemoreceptors
Cerebral cortex	Higher cortical input (e.g., anticipatory nausea with chemotherapy)

Common Causes

Gastrointestinal

Gastroenteritis, peptic ulcer disease, gastroparesis
Bowel obstruction, appendicitis, pancreatitis, hepatitis
GERD, achalasia

Systemic / Metabolic

Diabetic ketoacidosis (DKA), uremia, hypercalcemia
Adrenal insufficiency, thyroid disease

CNS

Raised intracranial pressure (ICP), meningitis, migraine
Vestibular disorders (labyrinthitis, Meniere's disease, BPPV)

Medications / Toxins

Opioids, NSAIDs, chemotherapy, antibiotics (especially erythromycin), digoxin toxicity

Other

Pregnancy (hyperemesis gravidarum)
Cyclic vomiting syndrome
Cannabinoid hyperemesis syndrome
Psychogenic / functional (chronic nausea and vomiting syndrome)

Clinical Assessment

History — key questions:

Timing: acute vs. chronic (>4 weeks)
Pattern: episodic vs. continuous
Relation to meals, position, medications
Associated symptoms: fever, abdominal pain, headache, vertigo, weight loss
Recent travel, sick contacts

Red flag features (warrant urgent investigation):

Projectile vomiting or bilious vomiting
Blood in vomit (hematemesis)
Severe abdominal pain or rigidity
Signs of raised ICP (headache, papilledema, neurological deficits)
Significant dehydration, weight loss

Differentiating vomiting from similar conditions (Chronic Nausea and Vomiting, p. 10):

Feature	Vomiting	Regurgitation	Rumination
Retching	Yes	No	No
Effort	Active	Effortless	Effortless
Timing	Variable	Often postprandial	Shortly after meals

Diagnostic Approach

Acute vomiting:

Basic labs: BMP (electrolytes, BUN/Cr, glucose), LFTs, lipase
Urine hCG (women of childbearing age)
Imaging if obstruction or acute abdomen suspected (AXR, CT abdomen)

Chronic vomiting (>4 weeks):

Rule out secondary causes (metabolic, structural, drug-induced)
Differentiate from regurgitation and rumination
If structural/motility workup negative → consider gut-brain interaction disorders:
- Cyclic vomiting syndrome — episodic vomiting with symptom-free intervals
- Cannabinoid hyperemesis syndrome — in regular cannabis users
- Chronic nausea and vomiting syndrome — continuous, non-episodic

Management

General / Supportive:

Oral or IV rehydration; correct electrolyte imbalances (hypokalemia, metabolic alkalosis)
NPO if severe; advance diet as tolerated

Antiemetic pharmacotherapy (targeted by mechanism):

Drug Class	Examples	Best For
5-HT₃ antagonists	Ondansetron, granisetron	Chemotherapy-induced, post-op
Dopamine antagonists	Metoclopramide, prochlorperazine, haloperidol	Gastroparesis, CTZ-mediated
Antihistamines	Dimenhydrinate, meclizine	Vestibular/motion sickness
Anticholinergics	Scopolamine	Motion sickness
NK₁ antagonists	Aprepitant	Chemotherapy-induced
Corticosteroids	Dexamethasone	Chemotherapy-induced (adjunct)
Cannabinoids	Dronabinol	Refractory chemotherapy-induced

Treat the underlying cause whenever identified (e.g., prokinetics for gastroparesis, antibiotics for H. pylori, discontinue offending drug).

When to refer / admit: Signs of dehydration, inability to maintain oral intake, hematemesis, suspected surgical abdomen, or failure of outpatient management.

Loose stools history

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loose stools diarrhea history taking clinical features

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acute chronic diarrhea etiology differential diagnosis

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History Taking: Loose Stools / Diarrhea

A structured history is the cornerstone of diagnosing the cause of loose stools. The key is distinguishing acute vs. chronic, then narrowing the differential.

Definition

Loose stool: defecated material that takes the shape of its container (Prevention and Treatment of OI in HIV, p. 16)
Diarrhea: ≥3 loose/watery stools per day, or increased frequency beyond the patient's normal (Harrison's, p. 299)
Acute: <4 weeks | Chronic: ≥4 weeks

History Framework

1. Onset & Duration

Sudden vs. gradual onset
Exact duration — separates acute from chronic
Any previous similar episodes

2. Stool Characteristics

Feature	Clinical Relevance
Watery, large volume	Small bowel / secretory cause
Small volume, frequent, urgent	Large bowel / colonic cause
Bloody (hematochezia)	Infectious colitis, IBD, ischemic colitis, colorectal malignancy
Pale/fatty/oily (steatorrhea)	Malabsorption (celiac, pancreatic exocrine insufficiency)
Mucus	IBD, irritable bowel syndrome (IBS)
Nocturnal diarrhea	Organic disease (IBD, microscopic colitis) — rules against IBS

3. Frequency & Severity

Number of stools per day
Severe: ≥6 loose stools/day ± systemic signs (fever, orthostatic hypotension, blood in stool)

4. Associated Symptoms

Fever → infectious, IBD
Abdominal pain / cramping → location, relation to defecation (relieved = IBS; worsened = IBD/infection)
Nausea/vomiting → gastroenteritis, toxin-mediated
Tenesmus (feeling of incomplete evacuation) → rectal/sigmoid pathology
Weight loss → malignancy, malabsorption, chronic infection, IBD
Bloating / flatulence → malabsorption, IBS, SIBO

5. Epidemiological / Exposure History

Travel (within last 4 weeks) → traveler's diarrhea (E. coli, Giardia, Campylobacter, Salmonella)
Contaminated food/water intake; sick contacts → foodborne illness
Antibiotic use (within 8–12 weeks) → Clostridioides difficile (CDI)
Hospital or healthcare exposure → CDI, nosocomial pathogens
Raw/undercooked meat, eggs, seafood → Salmonella, Vibrio, Campylobacter

6. Past Medical History

Diabetes (diabetic diarrhea — autonomic neuropathy)
IBD, celiac disease, IBS
Previous GI surgery (e.g., cholecystectomy → bile acid diarrhea; bowel resection → short bowel)
HIV / immunosuppression (higher risk of opportunistic infections, more severe course)
Thyroid disease (hyperthyroidism → diarrhea)
Malignancy (carcinoid syndrome, colorectal cancer)

7. Medications

Antibiotics → CDI, direct GI side effects
Magnesium-containing antacids, laxatives (factitious or iatrogenic diarrhea)
Metformin, colchicine, SSRIs, proton pump inhibitors → diarrhea as side effect
Chemotherapy → chemotherapy-related diarrhea
Immunosuppressants → opportunistic GI infections

8. Dietary History

Lactose-containing foods (lactose intolerance)
Fructose, sorbitol (sugar alcohols in diet foods/chewing gum)
Gluten (celiac screening)
High-fat diet

9. Social History

Sexual history: anal intercourse → proctitis (Neisseria gonorrhoeae, Chlamydia, HSV)
Alcohol use: alcoholic diarrhea, liver disease
Occupation / animal contact: zoonotic infections (Brucella, Cryptosporidium)
Recreational drugs

10. Family History

IBD (Crohn's disease, ulcerative colitis)
Colorectal cancer / polyps
Celiac disease

Red Flag Features (Warrant Urgent Investigation)

Blood or pus in stool
Fever >38.5°C
Signs of dehydration / orthostatic hypotension
Age >50 with new-onset change in bowel habits
Nocturnal diarrhea
Significant unintentional weight loss
Immunocompromised state
Recent antibiotic use (CDI risk)

Quick Differential by Pattern

Pattern	Consider
Acute watery, no fever	Viral gastroenteritis, toxin-mediated food poisoning
Acute bloody + fever	Bacterial colitis (Salmonella, Campylobacter, Shigella, STEC)
Post-antibiotic	C. difficile
Post-travel	Traveler's diarrhea, Giardia, amoebiasis
Chronic fatty/oily	Malabsorption (celiac, pancreatic insufficiency)
Chronic bloody ± mucus	IBD (Crohn's / UC)
Chronic with no organic findings	IBS, microscopic colitis, functional diarrhea
Immunocompromised	Cryptosporidium, CMV, MAC, Isospora

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