What imaging modality is able to diagnose a bowel obstruction complicated by ischemia?
Ischemia may occur when the mesentery is twisted during a closed loop obstruction in a hernia or under an adhesion, compromising venous return and arterial inflow. Ischemia may also occur during any obstruction in which luminal dilation results in decreased or absent blood flow to the mucosa. CT is the best radiologic modality to identify bowel ischemia. CT diagnosis depends on identification of thick-walled bowel that either does not enhance or has a mural stratification pattern because of marked submucosal edema ( Figure 23-13 ). In some patients, there is increased attenuation of the bowel wall on unenhanced scans because of intramural hemorrhage. Enlargement of veins in the mesentery may be present in patients with venous obstruction. The mesentery may have increased attenuation because of edema.