Ulcerative colitis (UC) is a type of inflammatory bowel disease (IBD). It develops when the immune system attacks food, bacteria, and other substances in the large intestine (colon).

This causes inflammation that can permanently damage the colon lining.

Periods of UC symptoms are called flare-ups. Symptom-free periods are called remission. People with UC alternate between flare-ups and remissions.

Taking medications can help manage the immune response and bring down inflammation in your colon before it causes damage and complications. Some people may need surgery to remove damaged parts of their colon.

Read on to learn about six long-term complications of uncontrolled UC.

UC increases your risk of developing the bone-weakening disease osteoporosis. Up to 60% of people with IBD have thinner than average bones.

Severe inflammation in your colon or having part of your colon removed with surgery can make it harder for your body to absorb calcium and vitamin D. You need these nutrients to keep your bones strong.

Inflammation can also disrupt the process your body uses to rebuild new bone. Having weak bones increases your risk of fractures.

Taking corticosteroids can also contribute to osteoporosis. These medications reduce inflammation in the colon, but they can also weaken bones.

Eating a diet rich in calcium and vitamin D can help protect your bones. Doing weight-bearing exercises like walking up stairs and dancing also strengthens bones.

If a bone density test shows that you have weakened bones, your doctor can prescribe bisphosphonates or other medications to protect them. You may also need to reduce your use of steroids.

Constant inflammation in the intestine can eventually make cells turn cancerous. People with UC have a higher risk of getting colorectal cancer than people without the disease.

Your likelihood of developing cancer does increase after you’ve had the condition for 8–10 years.

But overall, your risk is low. Most people with UC will never get colorectal cancer.

You’re more likely to get colorectal cancer if you have:

  • severe inflammation in your colon
  • a family history of colorectal cancer

It’s important for people who have had UC for more than 8 years to get screened every 1–2 years with a colonoscopy. This test uses a long flexible tube to find and remove abnormal tissue in your lower intestine.

Primary sclerosing cholangitis (PSC) is inflammation and scarring in the bile ducts. These tubes carry the digestive fluid bile from your liver to your small intestine. PSC is common in people with UC.

Scars can make the bile ducts narrow. The narrowing causes bile to back up in the liver. Over time, the liver can become scarred and damaged enough to need a transplant.

Toxic megacolon is a rare but dangerous complication of UC. It happens when gas becomes trapped in the colon and makes it swell up.

The colon can become so enlarged that it breaks open and releases bacteria into the blood. The bacteria can cause a serious blood infection called septicemia. If you suspect you have a swollen colon, seek medical help immediately.

Symptoms of toxic megacolon include:

  • belly pain and swelling
  • fever
  • rapid heart rate

Doctors treat toxic megacolon with medications to bring down swelling and prevent infection. If treatments don’t work, you may need surgery to remove part or all of your colon.

Inflammation and sores can weaken the colon wall so much that it eventually develops a hole. This is called a perforated colon.

A perforated colon usually happens because of toxic megacolon. It’s a medical emergency.

Bacteria that live in your intestine can get out through the hole into the abdomen. These bacteria can cause a serious infection called peritonitis. If this happens, you’ll need surgery to close the hole.

Damage to the colon can cause bleeding. You may notice the blood in your bowel movements. Bloody stools are a main symptom of UC.

The bleeding can be severe enough to cause anemia — a drop in red blood cells that carry oxygen throughout your body. It causes symptoms like fatigue and shortness of breath.

UC symptoms come and go, but the condition is chronic. To lower your risk for complications, follow the treatment plan your healthcare team has prescribed.

Also, talk with your doctor about lifestyle changes that can help you manage your condition.