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Ulcerative colitis and Crohn's disease are the most common types of inflammatory bowel disease. Ulcerative colitis affects only the colon and rectum. Crohn’s can affect any part of the digestive tract. To learn more about Crohn’s disease, see the topic Crohn’s Disease.

What is ulcerative colitis?

Ulcerative colitis is a disease that causes inflammation and sores (ulcers) in the lining of the large intestine, or colon. It usually affects the lower section (sigmoid colon) and the rectum. But it can affect the entire colon. In general, the more of the colon that’s affected, the worse the symptoms will be.

See a picture of the colon.

Ulcerative colitis can affect people of any age, but most people who have it are diagnosed before the age of 30.

What causes ulcerative colitis?

Experts are not sure what causes ulcerative colitis. They think it might be caused by the immune system overreacting to normal bacteria in the digestive tract. Or other kinds of bacteria and viruses may cause the disease.

Ulcerative colitis is not caused by stress, as people once thought. But if you have ulcerative colitis, stress can make it worse.

You are more likely to get ulcerative colitis if other people in your family have it.

What are the symptoms?

The main symptoms are:

• Belly pain or cramps.
• Bloody diarrhea or an urgent need to have a bowel movement.
• Bleeding from the rectum.

Some people also may have a fever, may not feel hungry, and may lose weight. In severe cases, people may have diarrhea 10 to 20 times a day.

Ulcerative colitis can also cause other problems, such as joint pain, eye problems, or liver disease. But these symptoms are more common in people who have Crohn’s disease.

In most people, the symptoms come and go. Some people go for months or years without symptoms (remission). Then they will have a flare-up. About 5 to 10 out of 100 people with ulcerative colitis have symptoms all the time.¹

Ulcerative colitis sometimes leads to more serious problems. It can cause scarring of the bile duct. This can lead to liver damage. In rare cases, severe disease causes the colon to swell to many times its normal size (toxic megacolon). This can be deadly and needs emergency treatment.

People who have ulcerative colitis for 8 years or longer have a greater chance of getting colon cancer.² Talk to your doctor about your need for cancer screening. Screening tests help find cancer early, when it is easier to treat.

How is ulcerative colitis diagnosed?

To diagnose ulcerative colitis, doctors ask about the symptoms, do a physical exam, and do a number of tests. Testing can help the doctor rule out other problems that can cause similar symptoms, such as Crohn’s disease, irritable bowel syndrome, or diverticulitis.