. Only 40% of the computed tomographic scans were diagnostic for bowel perforations: 50% of them showed suggestive signs, and 10% were considered as negative. Persistence of abdominal signs indicated peritoneal lavage. By using cell count ratio in diagnostic peritoneal lavage and/or increased lavage amylase activity, presence of particulate matter and/or bacteria in the lavage fluid, all patients with intraperitoneal bowel perforation were diagnosed accurately before operation.