Acute Mesenteric Ischemia: Imaging Findings and Mimics

Acute mesenteric ischemia is a rapidly life-threatening condition in which the radiologist may play a crucial role in early diagnosis and thus improve patient outcomes. Acute mesenteric ischemia can occur from arterial embolism or thrombosis, venous occlusive, or nonocclusive etiologies. Key findings for acute arterial occlusion include hypoenhancing bowel, which is usually not thickened or dilated. Venous occlusion often results in a hyperenhancing, thickened, and dilated bowel. Nonocclusive mesenteric ischemia should be considered in the appropriate clinical context, when there is no vascular occlusion on CT, and when there is involvement of watershed regions without specific vascular territory abnormalities. Venous congestion and increased vascular permeability can result in mesenteric edema and ascites; however, it is not predictive of mesenteric ischemia severity. Pneumatosis alone may not indicate presence of nonviable bowel; however, pneumatosis with portal venous gas or pneumoperitoneum has high sensitivity for nonviable bowel. Clinical history and laboratory results can often help differentiate between acute mesenteric ischemia and its mimics, such as inflammatory bowel disease, enteritis, and radiation injury.