Intraabdominal abscess is a recurrent problem that deserves attention. Some use the term “subphrenic” synonymously with intraabdominal, although most use the term subphrenic to refer only to abscess just below the diaphragm. The most common etiologies are postoperative complications of biliary tract or peptic ulcer surgery, penetrating abdominal trauma, and perforated appendix. Some 80%-90% of cases occur intraperitoneally. The spaces above and below the liver are the most common locations. About 25% of abscesses are located on the left side. The percentage of multiple abscesses ranges from 5%-40%. Bacteroides, E. coli, S. aureus, and streptococci are the most frequent organisms.
X-ray film shows pleural effusion in about 60%-80% of cases (range, 43%-89%), elevated diaphragm in about 70% (range, 34%-82%), and gas in the abscess in about 25%-50% (range, 9%-61%). Atelectasis and pneumonia are frequent in the closest lung base.
Computerized tomography (CT), gallium radioisotope scanning, and B-mode gray scale ultrasound may assist in diagnosis and localization of intraabdominal abscess. Of these, CT is probably the most sensitive, with approximately 90%-93% success rate (literature range, 82%-99%). Gallium 67 scanning has about 85% overall sensitivity (literature range, 75%-95%). The great advantage of gallium is total body scan capability with detection of inflammatory lesions located anyplace in the body (e.g., dental abscess, acute cholecystitis, or arthritis and osteomyelitis) rather than only intraabdominal infection when the scan is ordered for suspicion of intraabdominal abscess. There are major disadvantages, however. Gallium is excreted in the feces beginning about 12 hours after injection, so that bowel cleansing by laxatives and enemas (similar to barium enema preparation) is necessary and may have to be repeated. Scanning is usually performed 48 hours after injection, and the scan may have to be repeated if residual isotope is detected in the colon. This means that the study may take several days to complete. A certain percentage of various tumors may concentrate gallium and simulate abscess. There is normal uptake of isotope by the skeleton, liver, and spleen. B-mode gray scale ultrasound also has about 85% accuracy in detection of abdominal abscess and is less expensive than CT or gallium scanning. However, ultrasound in general gives better results in examining relatively small areas than in screening the entire abdomen. Ribs and air within the intestines may interfere.