Ischemic colitis is defined by a compromise in blood flow to the colon that leads to ischemic injury, which can result in mucosal ulceration, hemorrhage, and potentially perforation. Hypoperfusion is the most common etiology, leading to nonocclusive colonic ischemia. This occurs most frequently in the watershed regions, which have limited collateral blood supply. Ischemic colitis may also be due to occlusive thrombi in the mesenteric arteries or veins, especially in older individuals with comorbidities such as cardiovascular disease.

The incidence of ischemic colitis is at least 16 per 100 000 people / year; however, the true incidence is likely greater, as many people may not recognize the transient symptoms of ischemic colitis. It is believed that colonic ischemia may be more prevalent in women.

Typical presenting symptoms include lower abdominal pain and bloody diarrhea. The presentation can be acute or chronic (more often involving the rectum). Risk factors for the development of ischemic colitis include smoking, atherosclerosis, aortoiliac surgery, myocardial infarction, hemodialysis, and hypercoagulable state.