Although multiple causes of intra-abdominal abscesses exist, the following are the most common:
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Perforation of viscus, which includes peptic ulcer perforation [2]
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Perforated appendicitis and diverticulitis
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Gangrenous cholecystitis
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Mesenteric ischemia with bowel infarction
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Pancreatitis or pancreatic necrosis progressing to pancreatic abscess [3]
Other causes include untreated penetrating trauma to the abdominal viscera and postoperative complications, such as anastomotic leakage [1, 4] or missed gallstones during laparoscopic cholecystectomy.
Microbiology includes a mixture of aerobic and anaerobic organisms. The most commonly isolated aerobic organism is Escherichia coli, and the most commonly observed anaerobic organism is Bacteroides fragilis. [5] A synergistic relationship exists between these organisms. In patients who receive prolonged antibiotic therapy, yeast colonies (eg, candidal species) or a variety of nosocomial pathogens may be recovered from abscess fluids.
Skin flora may be responsible for abscesses after a penetrating abdominal injury. Neisseria gonorrhoeae and chlamydial species are the most common organisms involved in pelvic abscesses in females as part of pelvic inflammatory disease. The type and density of aerobic and anaerobic bacteria isolated from intra-abdominal abscesses depend upon the nature of the microflora associated with the diseased or injured organ.
Microbial flora of the GI tract shifts from small numbers of aerobic streptococci, including enterococci and facultative gram-negative bacilli in the stomach and proximal small bowel, to larger numbers of these species, with an excess of anaerobic gram-negative bacilli (particularly Bacteroides species) and anaerobic gram-positive flora (streptococci and clostridia) in the terminal ileum and colon.
Differences in microorganisms observed from the upper portion of the GI tract to the lower portion partially account for differences in septic complications associated with injuries or diseases to the upper and lower gut. Sepsis occurring after upper GI perforations or leaks causes less morbidity and mortality than sepsis after leaks from colonic insults.
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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).
