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Source: DiPiro JT and Howdieshell TR. Intraabdominal Infections. In: DiPiro, JT, Talbert RL, Yee GC, Matzke GR, Wells BG, Posey LM. Pharmacotherapy: A Pathophysiologic Approach. 8th ed. Accessed June 28, 2012.

  • Intra-abdominal infection
  • Spontaneous bacterial peritonitis

  • Acute, inflammatory response of peritoneal lining to microorganisms, chemicals, irradiation, or foreign body injury
    • Primary peritonitis: intra-abdominal focus may not be evident.
    • Secondary peritonitis: focal disease process evident.
    • Abscess: purulent collection of fluid separated from surrounding tissue by wall consisting of inflammatory cells and adjacent organs.
      • Usually contains necrotic debris, bacteria, and inflammatory cells.

  • Table 1 summarizes many potential causes of bacterial peritonitis.
  • Causes of intra-abdominal abscess overlap those of peritonitis.
    • May occur sequentially or simultaneously.
    • Appendicitis most frequent cause of abscess.
  • Primary peritonitis most commonly associated with end-stage alcoholic cirrhosis.

Table 1. Causes of Bacterial Peritonitis

  • Peritonitis
    • Primary peritonitis
      • Bacteria enter abdomen:
        • Via bloodstream or lymphatic system
        • By transmigration through bowel wall
        • Through indwelling peritoneal dialysis (PD) catheter
        • Via fallopian tubes
    • Secondary peritonitis
      • Bacteria enter peritoneum or retroperitoneum as result of disruption of integrity of gastrointestinal (GI) tract caused by diseases or traumatic injuries.
      • Focal disease process
    • Inflammatory process within peritoneum involves peritoneal lining.
      • Fluid and protein shift into abdomen (called “third spacing”).
      • May cause hypotension, shock, and death.
  • Abscess
    • Forms through combined action of:
      • Inflammatory cells (e.g., neutrophils)
      • Bacteria
      • Fibrin
      • Other inflammatory mediators
    • Oxygen tension low within abscess, allowing anaerobic bacteria to thrive.

  • Primary peritonitis often caused by single organism.
    • Most commonly associated with end-stage alcoholic cirrhosis and with Escherichia coli.
    • In children, pathogen usually group A Streptococcus,Streptococcus pneumoniae, E. coli, or Bacteroides species.
    • With peritoneal dialysis (PD), infection most often caused by common skin organisms: Staphylococcus epidermidis, Staphylococcusaureus, streptococci, and diphtheroids.
  • Secondary peritonitis most often polymicrobial (Table 2).

Table 2. Pathogens Isolated from Patients with Intra-Abdominal Infection

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