Intra-abdominal abscesses are localized collections of pus that are confined in the peritoneal cavity by an inflammatory barrier. This barrier may include the omentum, inflammatory adhesions, or contiguous viscera. The abscesses usually contain a mixture of aerobic and anaerobic bacteria from the gastrointestinal (GI) tract.
Bacteria in the peritoneal cavity, in particular those arising from the large intestine, stimulate an influx of acute inflammatory cells. The omentum and viscera tend to localize the site of infection, producing a phlegmon. The resulting hypoxia in the area facilitates the growth of anaerobes and impairs the bactericidal activity of granulocytes. The phagocytic activity of these cells degrades cellular and bacterial debris, creating a hypertonic milieu that expands and enlarges the abscess cavity in response to osmotic forces.
If untreated, the process continues until bacteremia develops, which then progresses to generalized sepsis with shock.
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Percutaneous computed tomography (CT) scan–guided drainage of postoperative subhepatic collection.
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Contrast-enhanced computed tomography (CT) scan of infected pancreatic pseudocyst (which can develop from acute necrotizing pancreatitis and give rise to an abscess).
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A 35-year-old man with a history of Crohn disease presented with pain and swelling in the right abdomen. Figure A shows a thickened loop of terminal ileum adherent to the right anterior abdominal wall. In figure B, the right anterior abdominal wall, adjacent to the inflamed terminal ileum, is markedly thickened and edematous. Figure C shows a right lower quadrant abdominal wall abscess and enteric fistula (confirmed by the presence of enteral contrast in the abdominal wall).
