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Intraperitoneal infections result when normal anatomic barriers are disrupted. Organisms contained within the bowel or an intraabdominal organ enter the sterile peritoneal cavity, causing peritonitis and—if the infection goes untreated and the pt survives—abscesses.


Peritonitis is a life-threatening event that is often accompanied by bacteremia and sepsis. Primary peritonitis has no apparent source, whereas secondary peritonitis is caused by spillage from an intraabdominal viscus; the etiologic organisms and the clinical presentations of these two processes are different.


  • 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.


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.


  • Pathogenesis: Secondary peritonitis develops when bacteria contaminate the peritoneum as a result of spillage from an intraabdominal viscus.

  • Microbiology: Infection almost always involves a mixed flora in which gram-negative bacilli and anaerobes predominate, especially when the contaminating ...

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