Transmural Bowel Necrosis From Acute Mesenteric Ischemia and Strangulated Small-Bowel Obstruction: Distinctive CT Features

OBJECTIVE. The purpose of this study was to assess whether transmural bowel necrosis has distinct CT features based on the three main causes: occlusive acute mesenteric ischemia (AMI), nonocclusive AMI, and strangulated small-bowel obstruction (SBO). MATERIALS AND METHODS. From January 2010 to December 2017, the records of all patients with a pathologic diagnosis of transmural bowel necrosis were extracted from the pathology department database of a university hospital. The inclusion criteria for the study were presence of transmural bowel necrosis at pathologic examination and available contrast-enhanced CT images obtained within the 24 hours before surgery. Seventy-seven patients were finally included. The CT scans were retrospectively independently reviewed by two abdominal radiologists to identify the classic CT findings of transmural bowel necrosis. Statistical analyses were performed. RESULTS. Pneumatosis intestinalis was statistically more frequent in nonocclusive AMI (59%) than in occlusive AMI (29%) and strangulated SBO (7% (p < 0.01), as were superior mesenteric venous gas (55%, 29%, and 0%; p < 0.01) and portal venous gas (48%, 10%, and 0%; p < 0.01). Decreased or absent bowel wall enhancement was more frequent in AMI than in SBO (nonocclusive AMI, 83%; occlusive AMI, 81%; SBO, 56%; p = 0.02), as was thinned bowel wall (nonocclusive AMI, 52%; occlusive AMI, 48%; SBO, 18%; p = 0.02). Spontaneous hyperattenuation of the bowel wall was more frequent in strangulated SBO (41%) than in nonocclusive AMI (10%) and occlusive AMI (14%) (p < 0.01). CONCLUSION. Transmural bowel necrosis has distinct CT findings according to its three main causes. Occlusive AMI is characterized by an absence of bowel wall enhancement and less mesenteric fat stranding, nonocclusive AMI by a high prevalence of pneumatosis intestinalis and portal venous gas, and strangulated SBO by spontaneous hyperattenuation of the bowel wall and an absence of pneumatosis intestinalis and portal venous gas.