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Ischemic colitis is a disorder in which part of your colon (large intestine) becomes inflamed and injured. The cause is usually a disruption or decline in blood flow to your colon, which can interfere with its normal functions.

Impaired blood flow to your colon can be either sudden and brief, or long-term. While ischemic colitis causes mild symptoms in many cases, the condition can become severe. If the deprivation of oxygen-rich blood is chronic, serious damage can result, with ulcers along the lining of your colon. The condition can even become life-threatening. Although this condition can affect any part of your colon, it involves pain on the left side of the abdomen in most people with the condition.

Also known as colonic ischemia, ischemic colitis occurs most often in people age 50 and older. In older adults, ischemic colitis is one of the most common medical conditions affecting the large bowel. Because ischemic colitis can be serious, see your doctor as soon as possible if you have serious bowel symptoms.

Common signs and symptoms of ischemic colitis include:

• Abdominal pain, tenderness or cramping, usually localized to the lower left side of your abdomen; the onset can be sudden or gradual
• Low-grade fever
• Bright red or maroon-colored blood in your stool or, at times, passage of blood without stool
• A feeling of urgency to move your bowels
• Diarrhea
• Nausea
• Vomiting

Ischemic colitis involves inadequate blood supply reaching your colon. In acute cases, the most frequent cause is blood clots in the arteries leading to your colon. Chronic cases are usually associated with the buildup of fatty deposits (atherosclerosis) in the blood vessels leading to your colon.

In some people, ischemic colitis may be caused by or related to other medical conditions, including:

• Inflammation of the blood vessels (vasculitis)
• Protrusion of an organ or tissue into the surrounding tissue, interfering with the arterial as well as the venous blood supply to the intestine (hernia)
• Elevated sugar, or glucose, levels in the blood (diabetes mellitus)
• Easy blood clotting (hypercoagulable state)
• Radiation treatment to the abdomen

The role of medications
Certain medicines — for example, nonsteroidal anti-inflammatory drugs, estrogen replacement medications, blood pressure pills, digoxin and pseudoephedrine — also rarely can cause ischemic colitis as a side effect. A complication of the drug heparin is a decline in blood platelets (thrombocytopenia) with an unusual complication of thrombosis (clots) in the arteries and veins.

There have been recent reports of ischemic colitis developing in women taking the prescription drug tegaserod (Zelnorm). This medication is prescribed short term for a gastrointestinal disorder called irritable bowel syndrome, or IBS. Zelnorm carries an advisory from the Food and Drug Administration (FDA) asking doctors to prescribe the drug with care because of its association with reductions in blood flow and ischemic colitis. Another prescription drug, alosetron (Lotronex), also used by women with severe IBS, carries an FDA warning as well, noting its potential link to serious conditions such as ischemic colitis.

Other causes
Abdominal surgery, particularly when it involves repair of a bulging arterial wall (aneurysm) in the region, is occasionally followed by ischemic colitis. In some cases, ischemic colitis may be triggered by infections involving bacteria (such as Escherichia coli), viruses (cytomegalovirus) or parasites (Entamoeba histolytica).

Risk factors for ischemic colitis include:

• Age. The condition occurs with greatest frequency in older adults.
• Heart disease risk factors. The impaired blood flow responsible for ischemic colitis is more likely to occur in people who have traits or conditions commonly associated with coronary heart disease. These include tobacco use, high blood pressure, and elevated cholesterol and triglyceride levels.
• Certain medical conditions. Some disorders are considered predisposing factors that place you at greater risk of developing ischemic colitis, or they can aggravate it when it occurs. These include previous abdominal operations, heart failure, low blood pressure and shock.

If you develop symptoms that could suggest ischemic colitis, contact your doctor. Signs and symptoms such as bloody diarrhea and abdominal pain, for example, may indicate ischemic colitis. Because this disorder can be serious, prompt evaluation by your doctor is important.

Your doctor begins by taking a medical history and conducting a thorough physical examination. During the exam, he or she will check your abdomen for areas of tenderness. You also may undergo the following diagnostic procedures:

• Colonoscopy. A colonoscopy is considered the definitive test for diagnosing ischemic colitis. In this procedure, a flexible lighted tube is inserted into your rectum and guided into the colon. A tiny camera at the tip of the scope sends images of your colon to a video screen. Your doctor can then view the interior lining of your colon and detect any inflammatory tissue and ulcers.
• Biopsy. Sometimes, as part of a colonoscopy, your doctor may remove a small tissue sample (biopsy) from your colon for laboratory analysis. In ischemic colitis, swelling and bleeding may be present under the colon's lining (mucosal layers), and can be detected in the laboratory.

A colonoscopy can rule out other causes of inflammation in your colon, including certain infections, inflammatory bowel disease, inflammation of the walls of the intestines (diverticulitis) and colon cancer. If the inflammation is severe, your doctor may not be able to see your entire colon well or obtain adequate biopsies.

It's often necessary to have a repeat colonoscopy once the inflammation has subsided. This allows your doctor to be sure that nothing of concern is present, such as persistent inflammation, scarring or colon cancer.

Other diagnostic tests
Your doctor may also suggest these other procedures to make a diagnosis:

• X-rays of the abdomen and pelvis. These are often conducted in combination with a barium enema. In this process, a contrast material (liquid barium) is introduced into your colon through your rectum. Once your colon is coated with barium, a radiologist takes X-ray pictures of your intestines. These images, which can be viewed on a video monitor, can detect abnormalities within your colon and help distinguish ischemic colitis from other inflammatory conditions. Images that indicate ischemic colitis may show thickening (thumbprinting) of the wall of your colon.
• Abdominal arteriogram. This is an X-ray of the arteries in your abdomen. It can show narrowing or blockages in these vessels, which may indicate ischemic colitis. A contrast dye is injected into your arteries before the X-rays are taken to help produce clear images.
• Abdominal magnetic resonance imaging (MRI). This imaging test can provide excellent views of the blood vessels and show blockages that may indicate ischemic colitis.
• Abdominal computerized tomography (CT) scans. Doctors sometimes use these scans to rule out other conditions that can cause symptoms similar to ischemic colitis. This radiological test uses sophisticated X-ray technology to produce detailed cross-sectional images of your colon. Your doctor may be able to detect thickening of the colon wall on the scans.
• Blood tests. People with ischemic colitis may have an elevated white blood cell count (WBC) that occurs when the body is fighting an infection.
• Stool sample. Analysis of a sample of your stool in the laboratory may reveal bacteria and other infectious microorganisms associated with ischemic colitis.

Complications of ischemic colitis may include:

• Gangrene. Untreated ischemic colitis could lead to tissue death (gangrene) in your colon. Gangrene may develop three to four weeks after the initial impairment of blood flow to your colon and can result in death if you don't receive timely treatment.
• Bleeding. Ischemic colitis can also cause a hole (perforation) in your intestine or persistent bleeding.
• Pain and blockage. Even as healing occurs, ischemic colitis can lead to colon scarring and narrowing. This can cause chronic abdominal pain and blockage.
• Colon cancer. In rare cases, ischemic colitis is the first sign of colon cancer.
• Other rare complications. These may include the accumulation of pus in the colon (abscess) and an inflammation of the membrane of the abdominal wall (peritonitis).

The choice of treatment depends on the severity of your condition.

When ischemic colitis is mild, your doctor may prescribe medications to keep your blood pressure at normal levels, which will help facilitate blood flow to your colon. You may also need to take antibiotics to prevent infections from developing. Your doctor will treat any underlying health problems, such as heart failure, and may prescribe an aspirin a day.

With such conservative measures, symptoms often diminish in 24 to 48 hours in mild cases, without the need for hospitalization.

However, if you're dehydrated, you may need hospitalization to provide fluids and nutrients through your veins (intravenously). You may also need restrictions on food intake for a few days to let your intestines rest.

Your doctor will continue to monitor you regularly with follow-up colonoscopies to determine whether the disease has healed or progressed, and whether complications have developed. In mild cases, healing may occur in two weeks or less. In more severe cases, recovery can take as long as six months, and relapses can occur.

If you develop ischemic colitis before the age of 50 or have a history of blood clots, you could have a disorder increasing the tendency of your blood to clot. Your doctor may treat this with a blood thinner such as warfarin, which could help prevent the likelihood of future ischemic colitis episodes.

Surgery
Surgery may be necessary in some people with ischemic colitis. You may need surgery if you have abdominal tenderness and fever that are severe and persistent, despite initial conservative medical care.

You may also need surgery if you've developed a localized constriction in your arteries. Your doctor may also recommend surgery if bleeding associated with ulcers occurs or if there's a hole (perforation) in your colon. The diseased portion of your colon can be removed during surgery (surgical resection).

For gangrene and the blood infection (sepsis) that accompanies ischemic colitis, treatment is typically with broad-spectrum antibiotics, blood replacement (if there is considerable anemia), and surgical removal of the diseased sections of the bowel.

There are no proven preventive approaches for ischemic colitis.

However, if you have underlying conditions associated with a risk of ischemic colitis — including coronary heart disease and high blood pressure — make sure you're receiving ongoing treatment. Your doctor may recommend that you:

• Stop smoking
• Take cholesterol-lowering medication
• Treat high blood pressure
• Exercise regularly