Spontaneous Bacterial Peritonitis



  • Infection of ascitic fluid without an evident intra-abdominal surgically treatable source:
    • Ascitic fluid polymorphonuclear leukocyte count (PMN) >250/mL with a positive bacterial peritoneal fluid culture
  • Must be distinguished from secondary bacterial peritonitis (from an intra-abdominal visceral infection):
    • Nonsurgical management of secondary bacterial peritonitis carries 100% mortality
    • Surgical management of spontaneous bacterial peritonitis (SBP) carries 80% mortality
  • Up to 30% yearly incidence of SBP in patients with ascites


  • Mechanism:
    • Portal hypertension causes translocation of intestinal bacteria through edematous gut mucosa to the peritoneal cavity
    • Variceal bleeding increases the risk of SBP due to a compromised barrier between the gastrointestinal (GI) tract and blood stream
    • Transient bacteremia with low serum complement
    • Decreased host defense mechanisms
    • Impaired activity of reticuloendothelial system phagocytosis and opsonization
    • Can also seed ascitic fluid via bacteremia from extra-abdominal infections
  • Usually seen in the setting of cirrhosis:
    • Rare in other conditions causing ascites (e.g., nephrotic syndrome, CHF)
  • Predominant organisms:
    • 63% aerobic gram-negative (Escherichia coli, Klebsiella, others)
    • 15% gram-positive (Streptococci/Staphylococci)
    • 6–10% enterococci
    • <1% anaerobic
  • Gram-positives account for 50% of cases in patients who are on prophylactic therapy with fluoroquinolones

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