Intestinal ischemia is caused by a reduction in blood flow, which can be related to acute arterial occlusion (embolic, thrombotic), venous thrombosis, or hypoperfusion of the mesenteric vasculature causing nonocclusive ischemia.
Colonic ischemia is the most frequent form of intestinal ischemia, most often affecting the elderly . Approximately 15 percent of patients with colonic ischemia develop gangrene, the consequences of which can be life-threatening, making rapid diagnosis and treatment imperative. The remainder develops nongangrenous ischemia, which is usually transient and resolves without sequelae . However, some of these patients will have a more prolonged course or develop long-term complications, such as stricture or chronic ischemic colitis.
The diagnosis and treatment of patients can be challenging since colonic ischemia often occurs in patients who are debilitated and have multiple medical problems.
The clinical features, diagnosis, and treatment of ischemia affecting the colon and rectum will be reviewed here. Acute and chronic intestinal ischemia of the small intestine are discussed separately. (See "Acute mesenteric ischemia" and "Chronic mesenteric ischemia".)
BLOOD SUPPLY OF THE COLON
The circulation to the large intestine and rectum is derived from the superior mesenteric artery (SMA), inferior mesenteric artery (IMA), and internal iliac arteries (figure 1). The colorectal circulation is relatively constant except for rare individual anatomic variations . The mesenteric veins parallel the arterial circulation, draining into the portal venous system (figure 2). An extensive collateral circulation (figure 3) protects the intestines from transient periods of inadequate perfusion [4,5]. However, the "watershed" areas of the colon, which have limited collateral blood flow, such as the splenic flexure and rectosigmoid junction, are at risk for ischemia particularly related to hypoperfusion (figure 4) [6-8]. The anatomy of the intestinal circulation is discussed in detail elsewhere. (See "Acute mesenteric ischemia", section on 'Intestinal circulation'.)