Primary (Spontaneous) Bacterial Peritonitis

Epidemiology: Primary bacterial peritonitis (PBP) is most common among pts with cirrhosis (usually due to alcoholism) and preexisting ascites, but ≤10% of these pts develop PBP. PBP is also described in other settings (e.g., malignancy, hepatitis).
Pathogenesis: PBP is due to hematogenous spread of organisms to ascitic fluid in pts in whom a diseased liver and altered portal circulation compromise the liver's filtration function.
Microbiology: Enteric gram-negative bacilli such as Escherichia coli or gram-positive organisms such as streptococci, enterococci, and pneumococci are the most common etiologic agents.
- - A single organism is typically isolated.
- - If a polymicrobial infection including anaerobes is identified, the diagnosis of PBP should be reconsidered and a source of secondary peritonitis sought.
Clinical manifestations: Although some pts experience acute-onset abdominal pain or signs of peritoneal irritation, other pts have only nonspecific and nonlocalizing manifestations (e.g., malaise, fatigue, encephalopathy). Fever is common (~80% of pts).
Diagnosis: PBP is diagnosed if peritoneal fluid is sampled and contains >250 PMNs/µL.
- - Culture yield is improved if a 10-mL volume of peritoneal fluid is placed directly into blood culture bottles.
- - Blood cultures should be performed because bacteremia is common.
Prevention: Up to 70% of pts have a recurrence of PBP within 1 year. Prophylaxis with fluoroquinolones (e.g., ciprofloxacin, 750 mg weekly) or trimethoprim-sulfamethoxazole (TMP-SMX; one double-strength tablet daily) reduces this rate to 20%, but increases the risk of serious staphylococcal infections over time.

Treatment: Primary (Spontaneous) Bacterial Peritonitis

A third-generation cephalosporin (e.g., ceftriaxone, 2 g q24h IV; or cefotaxime, 2 g q8h IV) or piperacillin/tazobactam (3.375 g qid IV) constitutes appropriate empirical treatment.

The regimen should be narrowed after the etiology is identified.
Treatment should continue for at least 5 days, but longer courses (up to 2 weeks) may be needed for pts with coexisting bacteremia or for those whose improvement is slow.
Albumin (1.5 g/kg of body weight within 6 h of detection and 1.0 g/kg on day 3) improves survival rates among pts with serum creatinine levels ≥1 mg/dL, BUN levels ≥30 mg/dL, or total bilirubin levels ≥4 mg/dL.

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