What is the recommended diagnostic and treatment approach for suspected spontaneous bacterial peritonitis (SBP)?

Diagnostic and Treatment Approach for Suspected Spontaneous Bacterial Peritonitis (SBP)

A diagnostic paracentesis must be performed immediately in all patients with cirrhosis and ascites who are suspected of having SBP, with empiric antibiotic therapy initiated promptly after diagnosis based on an ascitic fluid neutrophil count >250/mm³, regardless of culture results. 1

Diagnostic Approach

When to Perform Diagnostic Paracentesis

• Mandatory scenarios for immediate paracentesis:
  • All cirrhotic patients with ascites at hospital admission, even without symptoms 1
  • Patients with signs of infection (fever, chills, abdominal pain/tenderness)
  • Patients with GI bleeding
  • Patients with shock or hemodynamic instability
  • Patients with worsening liver function
  • Patients with hepatic encephalopathy
  • Patients with acute kidney injury
  • Patients with worsening or refractory ascites 1

Paracentesis Procedure and Sample Collection

1. Ascitic fluid analysis must include:

   • Cell count with differential (neutrophil count is diagnostic)
   • Inoculation of at least 10 mL into blood culture bottles at bedside (before antibiotics)
   • Total protein and albumin for SAAG calculation
   • Gram stain 1

2. Concurrent blood cultures:

   • Draw blood cultures simultaneously with paracentesis to increase pathogen identification 1

Diagnostic Criteria

• Definitive SBP diagnosis: Ascitic fluid neutrophil count ≥250/mm³ 1
• Bacterascites: Positive culture with neutrophil count <250/mm³
  • If symptomatic or signs of infection: treat as SBP
  • If asymptomatic: repeat paracentesis; treat if repeat culture positive 1

Differentiating Secondary Bacterial Peritonitis

Secondary peritonitis (from perforated viscus) should be suspected if:

• Multiple organisms on culture
• Very high neutrophil count
• High ascitic protein concentration
• Localized abdominal symptoms/signs
• Inadequate response to therapy 1

Action: Obtain prompt CT scan and surgical consultation if secondary peritonitis is suspected 1

Treatment Approach

Empiric Antibiotic Therapy

• Start immediately after diagnosis (before culture results) 1

• First-line options:

  • Third-generation cephalosporins: Cefotaxime 2g IV every 8-12 hours or Ceftriaxone 1-2g IV daily 1
  • Alternative: Amoxicillin-clavulanic acid (IV then oral) 1

• Duration: 5-7 days is typically sufficient 1

Special Considerations for Antibiotic Selection

• For healthcare-associated/nosocomial SBP:
  • Consider broader coverage due to higher risk of multidrug-resistant organisms (MDROs)
  • Piperacillin-tazobactam or carbapenems may be needed 1
  • Tailor therapy based on local resistance patterns 1

Adjunctive Albumin Therapy

• Indicated in patients with:

  • Renal dysfunction
  • High risk of hepatorenal syndrome
  • Serum creatinine >1 mg/dL
  • BUN >30 mg/dL
  • Total bilirubin >4 mg/dL 1

• Dosing: 1.5 g/kg at diagnosis and 1 g/kg on day 3 1

Monitoring and Follow-up

Response Assessment

• Consider repeat paracentesis at 48 hours if:
  • No clinical improvement
  • Worsening clinical status
  • Suspicion of secondary peritonitis 1

Treatment Failure

• Defined as persistent symptoms and elevated neutrophil count after 48 hours of therapy
• Actions:
  • Broaden antibiotic coverage
  • Rule out secondary peritonitis with imaging
  • Consider fungal infection (rare but associated with high mortality) 1

Common Pitfalls to Avoid

1. Delaying paracentesis - Should be performed immediately upon admission or suspicion of SBP
2. Waiting for culture results - Start antibiotics based on neutrophil count >250/mm³
3. Missing secondary peritonitis - Consider when multiple organisms, very high neutrophil count, or poor response to therapy
4. Overlooking asymptomatic SBP - Up to 30% of SBP cases may be asymptomatic 2
5. Inadequate culture technique - Bedside inoculation into blood culture bottles increases yield to >90% 1
6. Neglecting to reassess - Failure to improve within 48 hours requires reevaluation and possible change in management

SBP carries significant mortality risk (approximately 20%) even with appropriate treatment 1, and survivors should be considered for liver transplantation evaluation as SBP indicates poor prognosis in cirrhotic patients 3.