Spontaneous bacterial peritonitis

Section: Emergency Curriculum: Curriculum, page 27

Definition

• Acute bacterial infection of peritoneal fluid

Epidemiology

• Can affect any age and gender
• Common associated with ascites

Aetiology

• Peritoneal dialysate
• Ascites

Risk factors

• Cirrhosis
• Prior SBP
• Ascitic fluid total protein concentrations <1g/dL
• Serum total bilirubin >2.5mg/dL
• Variceal haemorrhage
• PPI

Pathophysiology

• Proposed theory
  • Portal HTN leads to intestinal bacterial overgrowth and translocation
  • Via entry to mesenteric LNs this leads to bacteremia and ascitic fluid seeding
• Cause of bacterial inoculum not truly known
  • ?bacterial translocation from bowel lumen
  • Haematogenous in a immunocompromised patient

Bacteria

• Usually aerobic GN organisms (75%)
  • E.coli most common 50%
  • Gram positives - strep, enterobacter
  • Anaerobes uncommon - high oxygen tension of ascitic fluid
• Common SBP pathogens
  • E.coli
  • Klebsiella pneumo
  • Strep pneumo
  • Other strep
  • Enterobacter
  • Staph
  • Pseudomonas
  • Misc

Clinical

• High suspicion in patients with cirrhosis/ascites that are unwell
• AP and fevers/rigors
• Encephalopathy or impaired mental state
• Ascites
• Diarrhoea
• Tender and hypotensive with signs of hepatic failure

Investigations

• FBC/U+E/CRP/LFTs/Coags/blood cultures
• Urinalysis
• Diagnostic paracentesis - either aspirate direct or via Tenchkoff
  • Before commencing abx ideally
  • Ascitic fluid analysis
    • Cell count - neuts >500
    • Differential
    • Culture
  • If done early and early abx = reduced LOS and 3 month mortality
• USS - to facilitate paracentesis
• CT - to R/O hollow viscous perforation

Diagnosis

• Three things requried
  • Paracentesis neutrophils >250 cells/mm3
  • Positive paracentesis cultures
  • Exclusion of secondary cause
    • Differential Diagnosis
      • Secondary peritonitis → all the causes

Management

• Principles
  • Resuscitation - IVF
  • Confirm diagnosis - investigations
  • Source control - IV abx
• Emperic antibiotics
  • If >250 neutrophils
  • Start abx while awaiting blood cultures
• Adjust abx as per culture
• Permanently stop non selective beta blocker - has increased risk of mortality

Prognosis

• Higher risk of death with liver or renal disease
• Improved with early identification and abx

Exam Algorithm

• Paracentesis!!!
• Neuts >250 (cell differential and count)
• Culture (to facilitate narrowing abx spectrum later)
• Early abx if neuts >250 and clinical suspicion
• Complete 1-2/52 abx total - more important if positive count and culture