Ulcerative colitis is part of a group of diseases called inflammatory bowel disease (IBD).
It is when the lining of your large intestine (the colon or large bowel) and your rectum become red and swollen or inflamed. In most cases the inflammation begins in your rectum and lower intestine and moves up to the whole colon.
Ulcerative colitis does not normally affect the small intestine. But it can affect the lower section of your small intestine (the ileum).
The inflammation causes diarrhea, making your colon empty itself often. As the cells on the lining of the colon die and come off, open sores or ulcers form. These ulcers may cause pus, mucus, and bleeding.
In most cases, ulcerative colitis starts when you are between the ages of 15 and 30 years old. Sometimes children and older people get it. It affects both men and women and seems to run in some families (is hereditary).
Ulcerative colitis is a long-term, chronic disease. There may be times when your symptoms go away and you are in remission for months or even years. But the symptoms will come back.
If only your rectum is affected, your risk of colon cancer is not higher than normal. Your risk is higher than normal if the disease affects part of your colon, and greatest if it affects your whole colon.
In rare cases, when severe problems happen, ulcerative colitis can lead to death.
Experts don’t know what causes ulcerative colitis.
It may be that a virus or bacteria affect the body's infection-fighting system (immune system). The immune system may create abnormal redness and swelling (inflammation) in the intestinal wall that does not go away.
Many people with ulcerative colitis have abnormal immune systems. But experts don’t know if immune problems cause the disease. They also don’t know if ulcerative colitis may cause immune problems.
Having stress or being sensitive to some foods does not seem to cause ulcerative colitis.
Right now there is no cure except for surgery to remove the colon.