In a patient with decompensated cirrhosis and ascites, which investigation is mandatory before starting empirical antibiotic treatment for suspected spontaneous bacterial peritonitis (SBP)?
- A Blood culture only
- B Diagnostic paracentesis with ascitic fluid neutrophil count (PMN ≥ 250 cells/mm³ is diagnostic) ✓
- C Serum CRP > 10 mg/L is sufficient to diagnose SBP without paracentesis
- D Urinary sodium to serum creatinine ratio to exclude hepatorenal syndrome first
Correct answer: B. Diagnostic paracentesis with ascitic fluid neutrophil count (PMN ≥ 250 cells/mm³ is diagnostic)
Explanation
Spontaneous bacterial peritonitis is diagnosed by diagnostic paracentesis showing ascitic fluid PMN ≥250 cells/mm³, which mandates empirical antibiotics (cefotaxime 2g IV q8h or ceftriaxone). Antibiotics should not be delayed pending culture results. Serum CRP or fever alone is insufficient. Paracentesis is safe and should be performed in all cirrhotics presenting with ascites and any clinical deterioration, regardless of coagulopathy.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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