Intra-abdominal Infections

Three basic types of Intra-Abdominal Infections:

  1. Individual organ infections
  2. Generalized peritonitis
  3. Abscesses

Organ specific infections (these infections are the result of primary or secondary bacterial infections caused by enteric organisms in the hepatobiliary tree or intestinal tract):

  1. Appendicitis (appendix)
    1. Appendix removal remains the primary treatment.
      1. Preoperative prophylaxis:  Cefoxitin or Cefotetan
    2. If the appendix is perforated or is gangrenous, use broad spectrum antibiotic capable of covering both enteric gram-negative and anaerobe organisms
  2. Cholangitis (bile duct)
    1. Use broad spectrum antibiotic capable of covering both gram-negative and anaerobic pathogens
  3. Cholecystitis (gall bladder)
    1. Treatment should target gram-negative aerobes (ex. E. Coli & Klebsiella pneumoniae);  Use cefuroxime or ceftriaxone
    2. Severe cholecystitis:  use broader spectrum antibiotics that are capable of covering anaerobic pathogens
  4. Pancreatitis (Pancreas)
    1. Only infected necrotic pancreatitis requires treatment (most pancreatitis is not associated with an infectious process)

Patient-specific factors that increase susceptibility to infections in the peritoneal cavity:  hepatic failure, peritoneal dialysis, peritoneal trauma, & surgery.


  • Primary: occurs via direct introduction into the peritoneum (ex. peritoneal dialysis infection) or translocation into the peritoneal fluid (ex. hepatic failure)
    • Typically caused by a single pathogen
    • Antibiotic should have both gram-positive and gram-negative aerobic pathogens
      • Staphylococci are the main pathogen but gram-negative pathogens are increasing
    • Treatment is typically 5 days in patients with cirrhosis and ascites
    • Treatment is typically at least 14 days in patients peritoneal dialysis
      • Longer therapies have been suggested in infections associated with resistant pathogens
  • Secondary:  occurs from perforation of the GI tract
    • Abscess treatment:  drainage + antibiotics
      • Antibiotic should be broad spectrum have activity against gram-negative enteric pathogens and anaerobes (should cover Bacteroides fragilis)
      • If the abscess can’t be drained (due to location, size or the number of abscesses), antibiotic treatment alone may be used
    • Hospital-acquired infections are more likely to be caused by resistant-pathogens than community-acquired infections
      • Hospital acquired infections should be treated with antibiotics that have activity against Pseudomonas aeurginosa or methicillin resistant staph aureus (MRSA)
    • Treatment is typically 4-7 days (based on individual patient response)
      • Treatment has been continued for up to several weeks in some patients depending on the severity of infection, response to antimicrobial therapy, patient-specific conditions, etc
  • Tertiary:  persistent or severe recurrent peritonitis

Common pathogens responsible for intra-abdominal infections:

  • Gram-negative aerobes:  E. Coli
  • Gram-positive aerobes:  Streptococcus spp.
  • Anaerobes:  Bacteroides

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