Ischemic colitis (IC) is inflammation and injury to the colon caused by a temporary reduction in blood supply (ischemia). This lack of oxygen leads to cellular damage. The colon is susceptible to this injury because its blood flow can be diverted to other organs during systemic stress, such as low blood pressure. IC is the most frequent form of intestinal ischemia, often affecting people over age 60. While most cases are mild and resolve without permanent damage, severe episodes can cause tissue death and necessitate emergency surgery.
The Mechanism of Colonic Injury
The colon receives its blood supply primarily from the superior and inferior mesenteric arteries, which form a network of connecting vessels to ensure continuous flow. Ischemic colitis often develops when this network fails to compensate for a drop in blood pressure or a partial blockage of a vessel. The most vulnerable areas are called “watershed zones,” which are regions at the border between the territories supplied by two major arteries. The splenic flexure and the rectosigmoid junction are the two most common sites for ischemic injury because they have fewer collateral blood vessels to reroute flow.
Blood flow reduction is categorized as either occlusive or non-occlusive ischemia. Non-occlusive ischemia is the more common type, involving a temporary reduction in systemic blood pressure due to shock, heart failure, or dehydration, leading to a “low-flow state.” Occlusive ischemia, in contrast, involves a physical blockage of a major blood vessel, usually by an arterial blood clot or severe atherosclerosis, which directly cuts off the supply.
Advanced age and a history of cardiovascular disease, such as atherosclerosis, diabetes mellitus, and heart failure, are significant risk factors. Certain medications that constrict blood vessels, chronic constipation, and clotting disorders can also increase susceptibility to ischemic events.
Recognizing the Symptoms
Ischemic colitis typically begins with a sudden onset of abdominal discomfort and cramping pain. This pain is most often felt in the lower left side of the abdomen, corresponding to the splenic flexure and descending colon. Patients frequently experience a strong, urgent need to move their bowels shortly after the pain begins.
This initial pain is generally followed within 24 hours by bloody diarrhea, medically known as hematochezia. The blood passed is often bright red or maroon, and the amount is usually mild to moderate. Other symptoms can include nausea, a low-grade fever, and tenderness when pressure is applied to the abdomen.
The severity and location of the pain influence the prognosis. Pain that is disproportionately severe or localized to the right side of the abdomen is often associated with a more severe form of ischemia and a higher risk of complications. Any sudden, severe abdominal pain that prevents sitting still warrants immediate medical attention.
Diagnostic Procedures and Treatment Options
Diagnosing ischemic colitis requires clinical suspicion because its symptoms overlap with many other gastrointestinal conditions, such as infectious colitis or inflammatory bowel disease. A medical workup often begins with a computed tomography (CT) scan of the abdomen to rule out other acute emergencies. The CT scan may show segmental thickening of the colon wall, a common finding in IC.
A colonoscopy or flexible sigmoidoscopy is frequently performed to directly visualize the colon and confirm the diagnosis. This procedure can show characteristic signs of ischemic injury, such as ulcers, inflammation, and pale or bluish tissue. A biopsy may be taken during the endoscopy to differentiate IC from other forms of colitis.
Treatment depends on the severity of the injury. Most mild, transient cases are managed with supportive care, as the condition often resolves spontaneously. Supportive measures include resting the bowel by temporarily restricting food and drink, administering intravenous fluids, and treating any underlying conditions contributing to the low-flow state. Broad-spectrum antibiotics may also be given to prevent infection.
Surgical intervention is reserved for the minority of patients who develop severe complications. These cases involve tissue death (gangrene), a perforation in the colon wall, or the formation of a blockage. Surgery involves removing the irreversibly damaged section of the colon to prevent life-threatening sepsis.
Recovery and Reducing Future Risk
The prognosis for the majority of individuals who experience ischemic colitis is favorable, with about 80% to 85% of cases being transient and non-gangrenous. Symptoms typically begin to improve within 2 to 3 days, and the colonic tissue usually heals completely within one to two weeks. However, about 10% of patients may develop a long-term complication known as a colonic stricture.
A colonic stricture is a narrowing of the colon that occurs as scar tissue forms during the healing process, potentially leading to an intestinal obstruction. Follow-up imaging or endoscopy is often necessary to monitor for these strictures, which may require surgical resection if they cause significant symptoms.
Preventing a recurrence involves proactively managing the underlying conditions that compromise blood flow. This includes aggressive control of vascular risk factors such as high blood pressure, elevated cholesterol levels, and diabetes. Smoking cessation is also highly recommended. Additionally, physicians will review a patient’s medication list to identify and potentially discontinue drugs that restrict blood flow, such as certain vasoconstrictors.