What is colitis?

Colitis is inflammatory bowel disease that occurs in the large intestine. Inflammatory bowel disease is the chronic inflammation and irritation of tissue in the gastrointestinal tract. It can occur anywhere from the mouth to the anus, although it most often affects the intestines. When inflamed, the intestinal lining can become red, swollen, develop ulcers and bleed.

More than 1 million Americans have been diagnosed with inflammatory bowel disease, according to the American College of Gastroenterology. There are 10 new cases for every 100,000 people each year.

How dangerous is colitis?

In severe cases, colitis can lead to other conditions, including anemia from blood loss, ulcers, blockage or stricture of the intestinal passage and fistulas that can also lead to the formation of abscesses outside the intestine. A condition called toxic megacolon can occur when the large intestine widens and loses muscle tone. Colitis may also increase a patient's risk of developing colon cancer.

What's the difference between Crohn's disease and ulcerative colitis?

The two primary types of inflammatory bowel disease are Crohn's disease and ulcerative colitis. Crohn's disease can occur anywhere along the digestive tract and irritate all layers of tissue in the wall's lining. It occurs most commonly in both the small and large intestines. Ulcerative colitis occurs only in the large intestine, usually starting in the rectum, and affects only the inner intestinal lining.