What are the diagnostic criteria and treatment for Spontaneous Bacterial Peritonitis (SBP)?

Diagnosis and Treatment of Spontaneous Bacterial Peritonitis (SBP)

The diagnosis of SBP is established when the ascitic fluid absolute neutrophil count is greater than 250/mm³, and treatment should be initiated immediately with third-generation cephalosporins as first-line therapy in settings where multi-drug resistant organisms are not prevalent. 1, 2

Diagnostic Criteria for SBP

Clinical Presentation

• SBP presentation is highly variable:
  • Up to one-third of patients may be asymptomatic or present only with worsening liver function or encephalopathy 2
  • Common symptoms include abdominal pain, tenderness (with or without rebound), ileus, fever, chills, and signs of systemic inflammation 1
  • May present with worsening encephalopathy and/or acute kidney injury 1

Diagnostic Paracentesis

• Diagnostic paracentesis is mandatory in the following situations:
  • All cirrhotic patients with ascites admitted to the hospital emergently (even without symptoms) 1
  • Patients with signs/symptoms of infection 1
  • Patients with gastrointestinal bleeding 1
  • Patients with worsening liver or renal function 1
  • Patients with hepatic encephalopathy 1

Laboratory Diagnosis

1. Ascitic fluid analysis must include:

   • Neutrophil count (diagnosis established when >250/mm³) 1
   • Bedside inoculation of ascitic fluid into blood culture bottles (increases culture sensitivity to >90%) 1
   • Total protein concentration 2

2. Blood cultures:

   • Should be obtained simultaneously with paracentesis to increase the possibility of isolating the causative organism 1

3. Microbiology:

   • SBP is typically monobacterial (vs. polymicrobial in secondary peritonitis) 1
   • Most common organisms (60%) are gram-negative bacteria (E. coli, Klebsiella) 1
   • Recent shift toward gram-positive organisms (S. aureus, Enterococcus) and multidrug-resistant organisms, particularly in nosocomial infections 1

Treatment of SBP

Antibiotic Therapy

1. Initiate empiric antibiotics immediately after diagnosis, before culture results are available 1

   • Each hour of delay in initiating antibiotics in patients with septic shock increases mortality by 10% 1, 2

2. First-line antibiotic therapy:

   • Third-generation cephalosporins (cefotaxime 2g IV every 12 hours or ceftriaxone) 1
   • A 5-day therapy is as effective as a 10-day treatment 1

3. Alternative regimens:

   • Amoxicillin/clavulanic acid (IV then oral) has shown similar efficacy to cefotaxime 1
   • Oral ofloxacin for uncomplicated SBP (without renal failure, encephalopathy, GI bleeding, ileus, or shock) 1
   • For nosocomial infections or settings with high prevalence of multidrug-resistant organisms, broader coverage may be needed (carbapenems) 1

Adjunctive Therapy

• Albumin administration should be considered, particularly in patients with renal dysfunction or high risk of hepatorenal syndrome 2
  • Reduces hospitalization mortality (10% vs 29%) and renal failure (10% vs 33%) 1

Monitoring Response

• Consider a second diagnostic paracentesis at 48 hours to assess treatment efficacy 2
• If ascitic fluid neutrophil count fails to decrease to less than 25% of pre-treatment value after 2 days, consider treatment failure 1

Special Considerations

Bacterascites

• Defined as positive ascitic fluid culture with neutrophil count <250/mm³ 1
• If the patient exhibits signs of systemic inflammation, treat with antibiotics 1
• Otherwise, repeat paracentesis when culture results return positive; treat if neutrophil count rises to >250/mm³ 1

Spontaneous Bacterial Pleural Empyema

• May complicate hepatic hydrothorax 1
• Diagnostic thoracocentesis should be performed in patients with pleural effusion and suspected infection 1
• Diagnosis based on positive pleural fluid culture and neutrophil count >250/mm³ or negative culture with >500 neutrophils/mm³ 1

Secondary Bacterial Peritonitis

• Consider when polymicrobial infection is present or when there's inadequate response to antibiotics 1
• Appropriate radiological investigation (CT scan) should be performed 1

Prevention

• Patients who have had a previous episode of SBP have a 69% probability of recurrence within a year and benefit from prophylactic treatment 2, 3
• Norfloxacin has been used successfully for prophylaxis in high-risk patients 3

By promptly diagnosing and treating SBP according to these guidelines, mortality can be significantly reduced from the historical 30-50% rate 4, 5.