[Computed tomography in the study of gastrointestinal perforation]

Plain radiography is the method of choice in suspected perforating pneumoperitoneum. Nevertheless, especially when air collections are small, the technique must be very accurate, with patient mobilization and long examination times, which may be unfeasible in acute abdomen patients. To overcome these limitations, such cross-sectional imaging methods as US and especially CT are increasingly used. Our series consisted of 38 patients with gastrointestinal tract perforation examined 1990-94; thirty-one of them had surgical confirmation. CT had high sensitivity, demonstrating the presence of free intraperitoneal gas in more patients than conventional radiography (92% vs. 74%). Pneumoperitoneum was depicted between liver surface and anterior abdominal wall in 30 cases, in the subhepatic region in 17, posterior to the abdominal wall at paraumbilical level in 14, between the mesenteric folds in 8, in the pelvis in 7 and in other locations in 11. Extraluminal fluid collections were apparent in 79% of cases and contrast agent collections in 73%. The three most common findings were: intraperitoneal gas, fluid effusion and extraluminal contrast agent leaks (61.5%), gas and effusion (29%) and gas only (16%). The origin of the perforation was demonstrated in 82% of cases and its cause in 37%. CT was particularly useful in the diagnosis of clinically occult, of early and of confined perforations. Small gas bubbles, mild fluid effusion or minimum contrast agent leaks near perforation site are valuable signs. In selected cases CT can play an integrative role, thus improving the diagnostic accuracy of plain films.