How should spontaneous bacterial peritonitis be diagnosed and managed in a cirrhotic patient with ascites?

Diagnosis and Management of Spontaneous Bacterial Peritonitis in Cirrhotic Patients with Ascites

Perform diagnostic paracentesis immediately in all cirrhotic patients with ascites at hospital admission, and diagnose SBP when ascitic fluid neutrophil count exceeds 250 cells/mm³, then start empirical antibiotics without waiting for culture results. 1, 2

When to Perform Diagnostic Paracentesis

Paracentesis must be performed urgently in the following situations:

• All cirrhotic patients with ascites at hospital admission (even without symptoms, as 10% of hospitalized patients have SBP) 1
• Gastrointestinal bleeding (25-65% develop bacterial infections including SBP) 1
• Fever or signs of systemic inflammation (hypothermia, chills, tachycardia, tachypnea) 1
• Abdominal pain or tenderness 1, 3
• Hepatic encephalopathy 1
• Worsening liver or renal function 1
• Shock or hemodynamic instability 1, 2

Critical timing consideration: Each hour of delay in performing paracentesis increases in-hospital mortality by 3.3%. 3

Diagnostic Criteria for SBP

Gold Standard Test

• Ascitic fluid polymorphonuclear (PMN) neutrophil count >250 cells/mm³ is diagnostic of SBP 1, 2
• This can be performed by manual microscopy or automated flow cytometry 1
• Do not wait for culture results to initiate treatment 1, 2

Essential Ascitic Fluid Tests

Send ascitic fluid for:

• Cell count with differential (most critical test) 1, 2, 3
• Culture in blood culture bottles at bedside (improves yield but frequently negative) 1
• Total protein concentration 1
• Glucose, LDH (to differentiate secondary peritonitis) 1, 2
• Gram stain 4

Blood Cultures

• Obtain blood cultures before starting antibiotics in all patients with suspected SBP 1

Differentiating Secondary Bacterial Peritonitis from SBP

Secondary peritonitis requires surgical intervention and must be identified promptly. Suspect secondary peritonitis when:

• Multiple organisms on Gram stain or culture 1
• PMN count >1,000 cells/mm³ 4, 2
• At least 2 of the following "Runyon criteria":
  • Ascitic total protein ≥1 g/dL 2
  • Ascitic LDH > upper limit of normal 2
  • Ascitic glucose <50 mg/dL 2
• Localized abdominal symptoms or inadequate response to antibiotics 1

If secondary peritonitis is suspected, obtain CT scan immediately to identify perforation or abscess requiring surgery. 1

Empirical Antibiotic Treatment

First-Line Therapy

Start antibiotics immediately after diagnostic paracentesis if PMN >250 cells/mm³, without waiting for culture results. 1

• Cefotaxime 2g IV every 12 hours (most extensively studied, 77-98% resolution rate) 1
  • Alternative dosing: 4g/day is as effective as 8g/day 1
  • Duration: 5 days is as effective as 10 days 1

Alternative Regimens

• Amoxicillin-clavulanic acid (IV then oral) has similar efficacy to cefotaxime 1
• Ciprofloxacin (7 days IV, or 2 days IV followed by 5 days oral) 1
• Levofloxacin for uncomplicated cases not on fluoroquinolone prophylaxis 5

Antibiotic Selection Considerations

• Community-acquired SBP: Third-generation cephalosporin (cefotaxime) 1
• Healthcare-associated or nosocomial SBP: Consider broader coverage (piperacillin-tazobactam or carbapenem) due to increasing multidrug-resistant organisms 1, 6, 5
• Avoid aminoglycosides (nephrotoxic) 1

Albumin Administration

All patients with SBP should receive intravenous albumin in addition to antibiotics. 1

Dosing Protocol

• 1.5 g/kg body weight at diagnosis 1
• 1.0 g/kg on day 3 1

Evidence and Benefits

• Albumin reduces hepatorenal syndrome (HRS) from 30% to 10% 1
• Reduces mortality from 29% to 10% compared to antibiotics alone 1
• Most beneficial in patients with:
  • Serum bilirubin ≥68 μmol/L (4 mg/dL) 1
  • Serum creatinine ≥88 μmol/L (1 mg/dL) 1

The benefit is less clear in patients with bilirubin <68 μmol/L and creatinine <88 μmol/L, but current guidelines recommend albumin for all SBP patients until further data are available. 1

Monitoring Response to Treatment

• Consider repeat paracentesis at 48 hours if inadequate clinical response or if secondary peritonitis is suspected 1
• Expect clinical improvement within 48 hours in 94% of patients 7

Prophylaxis Strategies

Secondary Prophylaxis (After SBP Episode)

Patients who recover from SBP have 69% recurrence risk within one year and should receive long-term prophylaxis: 8

• Norfloxacin 400 mg once daily orally 1
• Ciprofloxacin 500 mg once daily orally 1
• Co-trimoxazole 800/160 mg once daily orally 1

Primary Prophylaxis in High-Risk Patients

Gastrointestinal bleeding:

• All cirrhotic patients with ascites and GI bleeding should receive prophylactic antibiotics (cefotaxime preferred, based on local resistance patterns) 1
• This prevents SBP development and reduces rebleeding rates 1

Low ascitic protein:

• Consider primary prophylaxis in patients with ascitic total protein <1.5 g/dL who have never had SBP 1

Common Pitfalls to Avoid

• Do not delay paracentesis for coagulation studies or platelet transfusion - routine correction is not recommended 6
• Do not rely solely on culture results - culture-negative neutrocytic ascites (CNNA) with PMN >250/mm³ should be treated identically to culture-positive SBP 1, 3
• Do not miss bacterascites - if PMN <250/mm³ but culture is positive and patient has signs of infection, treat with antibiotics 1
• Do not forget albumin - antibiotics alone are insufficient; albumin significantly improves outcomes 1
• Do not continue beta-blockers in patients with refractory ascites - these increase SBP risk 5
• Do not use acid suppressive medications unnecessarily - strongly associated with increased SBP risk 5

Prognosis

• Mortality with early diagnosis and treatment: approximately 20% 1, 3
• Treatment resolution rate: 73-77% with appropriate antibiotics 1, 7
• Patients who develop SBP should be evaluated for liver transplantation 5