Ischemic Colitis

Medically Reviewed by Zilpah Sheikh, MD on April 10, 2024
Written by Rita Colorito, Regina Boyle Wheeler, Amy Gopal
9 min read

Ischemic colitis is inflammation or injury in your large intestine, or colon . It results from a lack of blood flow to the area, usually caused by a blocked or narrowed artery.

You need blood flow to your colon because it brings oxygen that keeps your tissues alive. If the blockage goes on for too long, it can cause serious problems. But if you get treatment soon, you should heal quickly. Ischemic colitis is more common in people over 60, but younger people can get it, too. You may hear your doctor call it ischemic bowel disease.

The most common symptoms of ischemic colitis are:

  • Abdominal pain, usually on your left side (often described as cramping pain)
  • Bloody poop, but not severe
  • Diarrhea

You may also have:

  • An urgent need to poop, often during cramping
  • Nausea
  • Lack of appetite
  • Low fevers, less than 100 F
  • Swollen belly
  • Severe abdominal pain on your right side, often with rectal bleeding (right-side pain is often linked to worse outcomes)
  • Vomiting

Acute mesenteric ischemia (AMI) is a life-threatening condition that happens when there’s a sudden blockage of blood flow in the mesenteric vessels in your large or small intestines. It happens for two main reasons:

  • When a blood clot or piece of arterial plaque in your heart or aorta breaks off and gets lodged in the smaller arteries of your intestines. This is called an arterial embolism.
  • When a blood clot suddenly forms in the arteries or veins of your intestines. This is called an arterial thrombus.

Mesenteric venous thrombosis, once thought as the main reason for AMI, only accounts for 10% of AMI cases. It’s a blood clot in the mesenteric vein that connects your small intestine to your belly.

Ischemic colitis is the most common type of intestinal ischemia, or gut-based blood blockages. But AMI is not so common. It accounts for less than 1% of acute abdominal cases in emergency rooms. Both conditions can be hard to diagnose because the symptoms often look like many other abdominal conditions.

Most people with ischemic colitis have mild cases and recover well with treatment. About 15% of people with ischemic colitis can develop complications, which can turn fatal.

AMI, on the other hand, can turn fatal very quickly, often in just a few hours. Depending on the damage to your intestines, AMI has a mortality rate of 50%-90%.

Symptom differences

With ischemic colitis, your artery becomes blocked or narrowed over time. The reduced blood flow to your large intestine is gradual. So, you may not feel ischemic colitis symptoms right away.

For AMI, sudden severe abdominal pain is the first symptom. But when you press down on your belly, the pain is mild and doesn't get worse. That’s not the case with other abdominal disorders, such as appendicitis, where the pain gets worse when the area is pressed.

AMI requires emergency medical attention. The abrupt drop in blood flow causes immediate and serious damage. When blood flow is blocked for more than 6 hours, it can cause that part of your intestine to die. That can lead to septic shock, organ failure, and death. Quick diagnosis and treatment can increase your chances of long-term survival.

Doctors often can’t pinpoint the cause of ischemic colitis. But these things can raise your odds of getting it:

Heart attack. During a heart attack, something blocks the flow of blood to your heart. This may trigger an ischemic colitis attack.

Chronic constipation. This raises the pressure inside your colon and makes it hard for blood to flow. If you have irritable bowel syndrome with constipation, you may be at even more risk.

Hardening of the arteries (atherosclerosis). Fatty gunk can build up and clog the arteries in your intestines.

Very low blood pressure or flow. This causes colon arteries to tighten and send more blood to your brain. Several health problems can cause low blood pressure. However, dehydration, heart failure, large blood loss, and shock are the leading reasons.

Blood clot. A clot can form inside an artery wall or break off from somewhere else and move toward your colon. Certain health problems you get from your parents at birth can cause blood to clot too easily. Your doctor may order some tests to see if you have one of these conditions.

Bowel blockage. This can result from a hernia, scar tissue, or a tumor.

Hemodialysis. This can be related to underlying diabetes or low blood pressure caused by hemodialysis procedures.

Older age. Ischemic colitis mainly affects people who are 60 or older. Typically, older people are more likely to have the other risk factors that cause ischemic colitis.

Severe COVID-19 infection. People with severe COVID often get blood clots and reduced blood flow.

Sex. It’s not clear why, but women, or those assigned female at birth, appear to be more at risk.

Surgery to repair an aortic aneurysm (a bulge in the artery) can lead to ischemic colitis. Other operations in your belly or your circulatory system can also cause problems.

The risk also goes up if you’re a long-distance runner or triathlete. During a marathon, blood flow may shift away from your gut to meet the oxygen needs of your leg muscles. Dehydration ,  hyperthermia, and electrolyte imbalances could play a role, too.

It’s rare, but some medications can trigger an ischemic colitis attack. These include:

  • Drugs that cause constipation, including opioid painkillers and some heart and migraine drugs
  • Immunomodulators, such as certain drugs for hepatitis, multiple sclerosis, and rheumatoid arthritis
  • Illicit drugs, including amphetamines and cocaine
  • Pseudoephedrine, a decongestant
  • Estrogen

Ischemic colitis is a master of disguise. Its symptoms can mimic other conditions, including a flare of ulcerative colitis or Crohn’s disease. Those long-lasting conditions result from a problem with your immune system, not low blood flow.

Doctors may ask for any of these tests to decide if you have ischemic colitis:

Imaging tests .  CT scans use X-rays at different angles to get a detailed image of your colon and blood vessels. A CT of your abdomen is usually the first imaging test doctors order if you have symptoms of ischemic colitis. If you have pain on your right side, CT angiograms can help your doctor figure out whether it’s from ischemic colitis or AMI.

Colonoscopy. This test looks inside your colon. The doctor also may take tissue samples to confirm a diagnosis. Colonoscopy with biopsy is considered the gold standard to definitively diagnose ischemic colitis. It’s often used for people with ongoing or chronic ischemic colitis.

Stool samples. Doctors look for infections that may be causing your symptoms.

Blood tests. These can’t diagnose ischemic colitis. But they can check for proteins linked to intestinal damage and for blood clotting issues.

If you have a mild case (and most cases are mild), the inner lining of your colon is inflamed, sore, and bleeding. It usually heals on its own within 1-2 weeks.

People with ischemic colitis typically spend a few days in the hospital in the intensive care unit, where doctors can monitor your blood flow. It also helps your colon heal. While in the hospital, you may receive IV antibiotics  to prevent infection.

To give your colon a rest while it heals, you won’t be able to drink or eat anything for a few days. You’ll get IV fluids and electrolytes to keep you hydrated. Supplemental oxygen can also help your bowel to heal.

After your treatment, you may need another colonoscopy to make sure there are no lasting problems.

Most cases of ischemic colitis are mild. But 10%-20% of people develop complications such as gangrene and colonic necrosis, or tissue death. You can also develop a perforation or tear in your colon.

When this happens, you'll need surgery to repair your bowel or remove the dead tissue. While medical management of ischemic colitis is linked to a 6% chance of death, surgical intervention -- needed for more serious cases -- is linked to a 40% chance of death.

People with severe ischemia can develop chronic ischemic colitis. Your doctor will need to follow you closely to make sure you are healing. In some cases, chronic ischemic colitis can cause symptoms of a partial bowel block.

For most people, an ischemic colitis attack is a one-time thing -- it never happens again. In others, it can become an ongoing problem.

You might be able to prevent another episode. To stack the odds in your favor:

  • Stay hydrated, to avoid constipation and blood vessel constriction.
  • Discuss your medications with your doctor. If one medication triggered the problem, your doctor may know of others that will work better for you.
  • Maintain normal blood pressure, but avoid aggressive treatments for high blood pressure.
  • Stop smoking. It damages virtually all your organs, including blood vessels.

If you have heart disease, your doctor may recommend blood thinners. More clinical studies are needed before this becomes a general recommendation for all heart disease patients with ischemic colitis. People who also develop mesenteric venous thrombosis may also be put on blood thinners.

Systemic corticosteroids are not recommended to treat or prevent ischemic colitis. That's because they may worsen damage and cause a perforation or tear in the colon. Ongoing studies are looking at whether certain IV steroids given with IV antibiotics can help in cases of severe ischemic colitis.

This condition results from a blocked artery. If you have ischemic colitis, you should eat a low-fat diet similar to what people with heart disease eat. Multiple small meals may be a better option, too. You may notice pain after you eat a fatty meal.

Ischemic colitis is inflammation or injury to your large intestine (colon) that happens when blood flow is blocked. It’s the most common type of blood flow blockage in your intestines. Most people recover fully in 1-2 weeks but often require hospitalization in an intensive care unit for a few days to help the colon heal. In serious cases, ischemic colitis can cause gangrene, tissue death, or perforation in the colon. When this happens, you'll need surgery to remove the dead tissue or repair your bowel.

How painful is ischemic colitis?

The pain depends on the location of ischemic colitis. Most people have ischemic colitis on their left side, with painful abdominal cramping. If you get ischemic colitis on the right side of your abdomen, the pain is usually more severe and accompanied by rectal bleeding. Right-side pain is linked to a worse prognosis.

Is ischemic colitis fatal?

If you have ischemic colitis along with pain on your right side, or sudden belly pain that’s so severe you can’t find a comfortable position, head to the ER or call 911.

The artery feeding the right side of your colon also feeds part of your small intestine. A blockage there can quickly damage or kill tissue. If this life-threatening situation occurs, you'll need surgery to clear the blockage and remove the damaged part of the intestine.