AIM: To evaluate the positive predictive value of abdominal non-prepared computed tomography (CT) for diagnosing intestinal lumen or wall lesions in patients presenting to the emergency room (ER) with abdominal complaints. METHODS: For 1-year we prospectively evaluated all ER patients hospitalized after abdominal CT scan detected either intraluminal or intestinal wall lesions. These patients underwent colonoscopy serving as gold standard. Patients with prior abdominal pathology or CT findings of appendicitis or diverticulitis were excluded. RESULTS: Five hundred and sixty-eight abdominopelvic CT scans were performed in the ER, 96 had positive colonic findings. Sixty-two patients were excluded, 46 because of diverticulitis or appendicitis, 16 because of prior abdominal pathology. Of the remaining 34 patients, 14 did not undergo colonoscopy during hospitalization. Twenty eligible patients were included in the study. The positive predictive value of the CT scans performed in the ER was calculated to be 45% (95% CI 25-67). CONCLUSION: CT findings correlated with colonoscopic findings only in approximately half of the cases. Relying on non-prepared CT scan findings in planning patient management and colonoscopy may lead to unnecessary diagnostic work-ups. AIM: To evaluate the positive predictive value of abdominal non-prepared computed tomography (CT) for diagnosing intestinal lumen or wall lesions in patients presenting to the emergency room (ER) with abdominal complaints. METHODS: For 1-year we prospectively evaluated all ER patients hospitalized after abdominal CT scan detected either intraluminal or intestinal wall lesions. These patients underwent colonoscopy serving as gold standard. Patients with prior abdominal pathology or CT findings of appendicitis or diverticulitis were excluded. RESULTS: Five hundred and sixty-eight abdominopelvic CT scans were Sixty-two patients were excluded, 46 because of diverticulitis or appendicitis, 16 because of prior abdominal pathology. Of the remaining 34 patients, 14 did not undergo colonoscopy during hospitalization. Twenty eligible patients were The positive predictive value of the CT scans performed in the ER was ca lculated to be 45% (95% CI 25-67). CONCLUSION: CT findings correlated with colonoscopic findings only in approximately half of the cases. Relying on non-prepared CT scan findings in planning patient management and colonoscopy may lead to unnecessary diagnostic work -ups.