Spontaneous bacterial peritonitis

Background

• Primary infection of the ascitic fluid, diagnosed by ascites fluid with positive culture or with neutrophil count greater than 250

Microbiology

• Escherichia coli (43%)
• Klebsiella pneumoniae (11%)
• Streptococcus pneumoniae (9%), particularly affecting people with HIV and prepubertal girls
• Other streptococcal species (19%)
• Enterobacteriaceae (4%)
• Staphylococcus (3%)
• Pseudomonas (1%)
• Miscellaneous (10%)
  • Aeromonas hydrophila, in Korea
  • Peritoneal tuberculosis
  • Dimorphic fungi

Pathophysiology

• Intestinal bacterial overgrowth with increased intestinal permeability leads to translocation to intestinal lymph notes and bloodstream, which results in hematogenous seeding to ascitic fluid
• Only occurs in portal hypertension, not in other causes of ascites

Risk Factors

• Previous history of SBP
• Upper GI bleed
• Low sciatic protein
• Child-Pugh class

Clinical Manifestations

• Asymptomatic in 10%
• Fever (70%)
• Abdominal pain (60%)
• Hepatic encephalopathy (50%)
• Abdominal tenderness, usually without rigidity (50%)
• Diarrhea (30%)
• Ileus (30%)
• Shock (20%)
• Hypothermia (15%)

Variants

• Culture-negative neutrocytic ascites: usually caused by difficult-to-treat organisms like tuberculosis, and non-infective sources
• Monomicrobial non-neutrocytic bacterascites: early bacterial colonization
• Polymicrobial bacterascites: usually from traumatic paracentesis

Prognosis and Complications

• In-hospital mortality of about 33% in hospital
• 58% 6-month mortality

Investigations

• Diagnostic paracentesis with ascitic fluid sent for cell count with differential and culture
  • Neutrophil count < 250 rules it out
  • Culture usually monomicrobial
• Repeat paracentesis at 48h if ongoing concern

Management

• Ceftriaxone 1-2g IV q24h

Prevention

• Prophylaxis is indicated after even a single episode of SBP
  • TMP-SMX SS PO daily
  • Norfloxacin
• Possibly a role for primary prophylaxis