PNEUMOPERITONEUM IN PERITONEAL-DIALYSIS PATIENTS - SIGNIFICANCE OF DIAGNOSIS BY CT

Objective: Pneumoperitoneum diagnosed by plain radiography is often a sign of gastrointestinal perforation and is unusual (0.17%) in patient s on continuous ambulatory peritoneal dialysis (CAPD). These patients are prone to bacterial peritonitis, which can have overlapping clinica l findings with perforated viscus. Because CT is often used to screen symptomatic CAPD patients, the reliability of pneumoperitoneum as a di agnostic sign is examined. Materials and Methods: Records of 433 CAPD patients were examined; of these, 56 patients had had CT while on CAPD (rupture, 6; nonrupture, 50). Plain radiography and CT were examined for free air and fluid. Patients were classified according to the amou nt of free air detected. Results: Patients with ruptured viscus had pn eumoperitoneum in 5 of 6 cases by CT and 4 of 6 by plain radiography. Excluding free air, ruptured viscus could only be diagnosed in 1 of th e 6 patients by CT. Patients without rupture had pneumoperitoneum in 1 5 of 50 cases by CT and 2 of 46 by plain radiography. No instance of p neumoperitoneum was discovered on plain radiography and not CT. Conclu sion: Pneumoperitoneum was found by CT in 30% of nonrupture CAPD patie nts, therefore, CT appeared to be more sensitive than plain radiograph y for its detection. The presence, quantity, and distribution of free air are not helpful in separating perforations from nonperforations. T he lack of pneumoperitoneum on CT was found to be a useful but not abs olute diagnostic sign to exclude gastrointestinal rupture.