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PERITONITIS - Complete Exam Notes for Final Year MBBS

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DEFINITION

• Localised or diffuse
• Acute or chronic
• Bacterial, chemical, or sterile

The most clinically useful classification is localised vs. diffuse.

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CLASSIFICATION / TYPES

A. By Extent

B. By Aetiology / Cause

• No obvious intra-abdominal source of infection
• Infection reaches peritoneum via haematogenous or lymphatic spread
• Subtypes:
  • Spontaneous Bacterial Peritonitis (SBP) - in cirrhosis/ascites
  • Primary Pneumococcal Peritonitis - in children (girls via vagina/Fallopian tubes)
  • TB Peritonitis - chronic form

• Results from perforation or breach of an abdominal viscus
• Causes include:
  • Perforated peptic ulcer
  • Perforated appendix
  • Perforated diverticulum
  • Anastomotic leak
  • Gangrenous bowel
  • Pelvic inflammatory disease (PID)
  • Biliary peritonitis (post-cholecystectomy)

• Persistent peritonitis after adequate treatment of secondary peritonitis
• Often involves low-virulence organisms (fungi, coagulase-negative staphylococci)
• Associated with high mortality in ICU patients

C. By Causative Agent

D. Routes of Peritoneal Infection (Exam Favourite)

1. GI tract perforation - perforated ulcer, appendix, diverticulum
2. Transmural translocation (without perforation) - pancreatitis, ischaemic bowel, SBP
3. Exogenous contamination - drains, open surgery, trauma, peritoneal dialysis
4. Female genital tract - PID, salpingitis
5. Haematogenous spread (rare) - septicaemia

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CLINICAL PRESENTATION

Symptoms

Signs

Localised vs. Diffuse Peritonitis - Key Differences

Exam tip: In obese patients or those on immunosuppressants, signs of peritonitis may be significantly masked.

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SPECIFIC TYPES IN DETAIL

1. Spontaneous Bacterial Peritonitis (SBP)

• Definition: Acute bacterial infection of ascitic fluid WITHOUT an identifiable intra-abdominal source
• Setting: Cirrhosis + ascites (most common), nephrotic syndrome
• Organisms: E. coli (Gram-negative, most common), Streptococci and Enterococci (Gram-positive)
• Presentation: Highly variable - patient may be asymptomatic, or have fever, abdominal pain, altered consciousness
• Diagnosis:
  • Paracentesis (diagnostic tap) - ESSENTIAL
  • PMN (Polymorphonuclear) neutrophil count ≥250 cells/mm³ in ascitic fluid = diagnostic
  • Culture positive in only 40% of cases (negative in up to 60%)
• Treatment:
  • 3rd generation cephalosporin (e.g. cefotaxime) - first line
  • Alternatives: Amoxicillin/clavulanic acid, Ciprofloxacin
  • Empirical treatment must start BEFORE culture results return

2. Primary Pneumococcal Peritonitis (Primary Peritonitis)

• Who: Children (especially girls), nephrotic syndrome, cirrhosis
• Route: Via vagina and Fallopian tubes (girls); blood-borne from respiratory or middle-ear disease
• Organisms: Haemophilus spp., Group A streptococci, pneumococci, rare Gram-negative bacteria
• Onset: Usually sudden
• Features:
  • Pain localised to lower abdomen initially
  • High fever (39°C or more)
  • Frequent vomiting
  • After 24-48 hours: profuse diarrhoea (characteristic) due to severe pelvic peritonitis
  • Increased urinary frequency
  • Peritonism less prominent than perforated viscus
• Management: Antibiotics + rehydration + surgery (laparotomy/laparoscopy) to confirm diagnosis and lavage

3. Biliary Peritonitis

• Causes: Post-cholecystectomy clip slippage from cystic duct, accessory duct bile leak, CBD/hepatic duct perforation
• Management:
  • Localised: Percutaneous drain + ERCP (stent across leak)
  • Diffuse/high-volume: Surgical exploration + lavage + drainage

4. Tuberculous (TB) Peritonitis

• Epidemiology: Common in resource-poor countries; rising in rich countries (migration, immunosuppression, HIV + Mycobacterium avium intracellulare)
• Routes of spread: Via GI tract (ileocaecal region) → mesenteric lymph nodes → peritoneum; or blood-borne (miliary TB)
• Forms:
  • Wet/Ascitic type (90%): Generalised or loculated ascites; multiple tubercle deposits on peritoneum
  • Dry/Plastic type (fibrotic): Loops of bowel/omentum matted together; may cause subacute intestinal obstruction; NO ascites
• Presentation: Insidious - abdominal pain, weight loss, abdominal distension, night sweats, malaise
• Diagnosis:
  • CT/ultrasound: ascites, lymphadenopathy, peritoneal/mesenteric/omental thickening
  • Ascitic fluid: Straw-coloured exudate, protein >25-30 g/L, WBC >500/mL, lymphocytes >40%
  • AFB smear: Often NOT diagnostic
  • Culture: Takes 4-8 weeks
  • Adenosine deaminase (ADA) activity in ascitic fluid - high sensitivity and specificity
  • Laparoscopy + peritoneal biopsy - gold standard (couples appearance + histology)
• Management: Nutritional/hydration support + systemic anti-TB therapy (4-drug regimen); surgery for complications (intestinal obstruction)
• Key point: TB peritonitis often diagnosed late. Must distinguish from peritoneal metastases (carcinomatosis) - may need biopsy.

5. Familial Mediterranean Fever (FMF)

• Autosomal recessive, autoinflammatory
• MEFV gene mutation (Arabs, Armenians, Turkish, Sephardic Jews)
• Episodic diffuse abdominal pain + tenderness + mild pyrexia + joint pain
• Symptoms resolve within 24-72 hours
• Long-term complication: Amyloidosis

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DIAGNOSIS

Investigations

• FBC - raised WBC (neutrophilia)
• CRP, ESR - elevated
• LFT, RFT, serum amylase (to exclude pancreatitis)
• Blood cultures
• Urine routine (exclude UTI)
• Pregnancy test in women of reproductive age

Exam pearl: CT abdomen is the investigation of choice for peritonitis. A lateral decubitus film can substitute for erect CXR when patient cannot stand.

Intraoperative Findings

• Peritoneum: Reddened, thickened, velvety texture
• Yellow/white fibrin plaques causing bowel loops to adhere
• Reactionary serous exudate (leukocytes + plasma proteins) → turbid → frank pus

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COMPLICATIONS

Early Complications

Late Complications

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MANAGEMENT (Summary)

Non-Surgical / Resuscitation

1. IV access + resuscitation - correct fluid/electrolyte imbalance
2. IV broad-spectrum antibiotics - cover Gram-negative, Gram-positive, anaerobes
3. Nasogastric tube - decompress bowel
4. Urinary catheter - monitor urine output
5. Analgesia (IV opioids)
6. Vital system support - ICU if septic shock/MODS

Surgical

1. Source control - remove/exclude the cause (close perforation, resect gangrenous bowel)
2. Peritoneal lavage ± drainage
3. Laparoscopy (preferred) or laparotomy depending on severity and cause

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HIGH-YIELD EXAM POINTS

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