Toxic Megacolon

Toxic megacolon is rare, but it’s an emergency. It can happen when you have a severe case of colitis, inflammation in your colon. Inflammation that penetrates to the muscles in your colon causes them to stop working. Food and gas build up inside, your colon walls widen and stretch, and toxins begin to leak out into your bloodstream.


What is toxic megacolon?

Toxic megacolon is a rare but serious complication of severe colitis. Colitis is inflammation in your colon (large intestine). Colitis typically affects the mucous lining of your intestine. But severe and prolonged inflammation can eventually spread to the deeper layers of your colon, including the muscles. This can begin to break down the structural integrity of your colon.

Deep inflammation disables the muscles in your colon wall that contract to move substances through. It causes those substances (food and gas) to build up in your colon while the walls weaken, stretch and widen (dilate). Ultimately, toxic substances build up inside your colon and leak through the weakened walls into your bloodstream. This causes systemic toxicity.


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What is the difference between toxic megacolon and other types of megacolon?

Other conditions can cause your colon to become blocked and backed up with food and gas, stretching and widening the walls. Large intestinal obstructions and pseudo-obstructions may cause megacolon. However, systemic toxicity may not always occur. Inflammatory and infectious colitis are often more associated with systemic toxicity, resulting in symptoms such as low blood pressure, fast heart rate and altered mental status.

What are the possible complications of toxic megacolon?

Toxic megacolon is a medical emergency that puts you at risk of several life-threatening complications, including:


How does toxic megacolon cause death?

Weakened and stretched colon walls are especially vulnerable to tearing. A perforation or rupture in your colon wall could lead to serious internal bleeding and infection in your abdomen (peritonitis). This can quickly spread to your bloodstream and puts you at risk of toxic shock. Severe abdominal pressure can also cause organ failure by depriving your organs of blood and oxygen.

Symptoms and Causes

What are the symptoms of toxic megacolon?

Symptoms may include:


What is the most common cause of toxic megacolon?

Technically, any type of colitis can lead to toxic megacolon if it’s severe enough. However, it’s most commonly associated with inflammatory bowel disease (IBD). IBD is an umbrella term for several conditions that cause chronic and incurable colitis. IBD that isn’t well managed with diet and medication is more likely to eventually penetrate to the deeper layers of your colon.

What causes toxic megacolon?

Toxic megacolon is a complication of severe colitis, which can have many causes. There are many different types of colitis that may lead to toxic megacolon, including:

  • Ulcerative colitis. Ulcerative colitis is one of the most common types of inflammatory bowel disease, and one of the most common causes of toxic megacolon. Most cases occur within the first few years after diagnosis.
  • Crohn’s disease. Crohn’s disease is another type of inflammatory bowel disease. It more often affects your small intestine, but can also affect your colon (large bowel). Crohn’s disease is highly susceptible to toxic megacolon in its early stages.
  • Ischemic colitis. Ischemic colitis is a side effect of intestinal ischemic syndrome, which is when your intestines aren’t getting enough blood supply. As this is a relatively difficult problem to solve, ischemic colitis has the opportunity to advance to toxic megacolon.
  • Radiation colitis. Colitis or enteritis is usually a short-term side effect of radiation therapy, but some people develop chronic symptoms that can lead to complications.
  • Infectious colitis. Infections from bacteria, parasites or viruses can cause colitis. Certain types may affect certain people more severely. Common food poisoning and stomach flu infections can cause severe colitis in some people. Those with compromised immune systems are especially vulnerable to cytomegalovirus.
  • Pseudomembranous colitis. The bacterium C. diff (clostridioides difficile) causes this type of infectious colitis. Pseudomembranous colitis is often mentioned as a risk for toxic megacolon. The infection commonly affects people taking antibiotics for a separate infection. The antibiotics kill helpful bacteria in your gut that usually keep the C. diff bacterium in check, allowing C. diff to run wild. C. diff infection can become severe very quickly.

What risk factors contribute to toxic megacolon?

You may be more likely to develop toxic megacolon if you have:

Certain medications that you may be taking can make conditions worse for toxic megacolon, including:

Diagnosis and Tests

How is toxic megacolon diagnosed?

Your healthcare provider will ask you about your symptoms and your complete history of health conditions and medications. Certain conditions or medications may make toxic megacolon more likely. Some medications, such as steroids, may mask the symptoms of toxic megacolon. They’ll examine you physically before moving on to more specific tests.

Your physical exam may show a swollen abdomen, abdominal tenderness and an overall appearance of toxic illness. Your healthcare provider may listen to your bowel for decreased bowel sounds resulting from decreased movement. They’ll take your vital signs to check for fever, low blood pressure and fast heart rate, which are all signs of toxicity.

Your provider will also need to take a blood test and imaging test of your abdomen to confirm your diagnosis. Imaging may mean an X-ray, an abdominal ultrasound or a CT scan. They’ll be looking for colon dilation and any related complications. The blood test will show evidence of deep inflammation by counting your red and white blood cells.

The criteria to diagnose toxic megacolon include:

In addition, your healthcare provider may want to test your blood or your poop for specific infections.

Management and Treatment

What is the treatment for toxic megacolon?

You’ll need treatment in the hospital for a few days. The goal of initial treatment is to stabilize your condition and reduce the severity of your colitis. If you have sepsis, you may need critical care, such as mechanical ventilation for respiratory failure or dialysis for kidney failure. Otherwise, treatment for toxic megacolon will typically begin with:

If your condition doesn’t improve with steroids, your provider may try another type of medication, such as an immune modulator. This may help reduce the overactive immune response that’s causing too much inflammation and too many white blood cells in your tissues.


About 50% of people may be successfully treated with medication alone. Others will need surgery, especially if there are life-threatening complications involved. Healthcare providers consult surgeons early on when someone has toxic megacolon to help in the decision-making. Your healthcare provider may judge that it’s safer to remove the affected portion of your colon to prevent further risk or complications. When you have a colectomy, you’ll probably need an ostomy as well.

An ostomy is an opening in your abdomen. Poop exits your body through the ostomy when your intestines aren’t working the way they should. You may need a temporary or permanent ostomy, depending on what kind of colectomy you have. Whether short-term or long-term, an ostomy can be a big adjustment to process, especially in an emergency setting.

Outlook / Prognosis

Can you survive toxic megacolon?

Your chances are good if you seek treatment soon enough. The overall survival rate for those treated for toxic megacolon is around 93%. Those who have complications, such as a perforation, have a survival rate closer to 75%. Complications mostly occur when toxic megacolon goes untreated for too long, so it’s important to recognize the seriousness of your condition.

A note from Cleveland Clinic

Toxic megacolon is a medical emergency that can develop quickly and unexpectedly. It’s more of a risk if you’ve been recently diagnosed with inflammatory bowel disease and the disease isn’t yet managed. But it can also happen during an acute infection, or in other cases of severe colitis. Pay attention if your usual symptoms begin to worsen or change.

If you begin to feel generally ill and toxic during severe colitis, seek medical attention right away. Early management is key to preventing life-threatening complications, and it may prevent the need for surgery. If you do need an emergency colectomy and ostomy, know that you’ll have ample support to help you adjust to these changes going forward.

Medically Reviewed

Last reviewed on 07/13/2022.

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