Inflammatory bowel disease (IBD) is the name of a group of disorders in which the intestines (small and large intestines or bowels) become inflamed (red and swollen). This inflammation causes symptoms such as:
Severe or chronic (almost all of the time) pain in the abdomen (belly)
Diarrhea - may be bloody
Unexplained weight loss
Loss of appetite
Bleeding from the rectum
Joint pain
Skin problems
Fever

Symptoms can range from mild to severe. Also, symptoms can come and go, sometimes going away for months or even years at a time. When people with IBD start to have symptoms again, they are said to be having a relapse or flare-up. When they are not having symptoms, the disease is said to have gone into remission.

The most common forms of IBD are ulcerative colitis and Crohn's (krohnz) disease. The diseases are very similar. In fact, doctors sometimes have a hard time figuring out which type of IBD a person has. The main difference between the two diseases is the parts of the digestive tract they affect.

Ulcerative colitis affects the top layer of the large intestine, next to where the stool is. The disease causes swelling and tiny open sores, or ulcers, to form on the surface of the lining. The ulcers can bleed and produce pus. In severe cases of ulcerative colitis, ulcers may weaken the intestinal wall so much that a hole develops. Then the contents of the large intestine, including bacteria, spill into the abdominal (belly) cavity or leak into the blood. This causes a serious infection and requires emergency surgery.

Crohn's disease can affect all layers of the intestinal wall. Areas of the intestines most often affected are the last part of the small intestine, called the ileum, and the first part of the large intestine. But Crohn's disease can affect any part of the digestive tract, from the mouth to the anus. Inflammation in Crohn's disease often occurs in patches, with normal areas on either side of a diseased area.

In Crohn's disease, swelling and scar tissue can thicken the intestinal wall. This narrows the passageway for food that is being digested. The area of the intestine that has narrowed is called a stricture (STRIK-choor). Also, deep ulcers may turn into tunnels, called fistulas (FISS-choo-luhss), that connect different parts of the intestine. They may also connect to nearby organs, such as the bladder or vagina, or connect to the skin. And as with ulcerative colitis, ulcers may cause a hole to develop in the wall of the intestine.

IBD is not the same as irritable bowel syndrome (IBS), although the symptoms can be similar. Unlike inflammatory bowel disease, IBS does not cause inflammation or damage in the intestines.

In many people with IBD, medicines can control symptoms. But for people with severe IBD, surgery is sometimes needed. With treatment, most people with IBD lead full and active lives.