Inflammatory bowel disease (IBD) is a term used to describe two similar, yet distinct conditions: Crohn's disease and ulcerative colitis. These diseases affect the digestive system and cause the intestines to become inflamed, develop ulcerations, bleed easily, scar, and sometimes narrow. Symptoms of IBD include abdominal pain, cramping, weight loss, fatigue, and diarrhea.

Crohn's disease can affect any part of the gastrointestinal tract from the mouth to the anus. "Patches" of inflammation appear, with healthy-appearing tissue between diseased areas. The inflammation of Crohn's disease can be deep; extending through every layer of affected bowel tissue (Crohn's disease is a "full-thickness" disease). Because of the tendency of Crohn's disease to recur after medical or surgical treatment, and the fact that it may be present in microscopic amounts even in the normal-appearing parts of the bowel, physicians generally state that they cannot cure this disease. Rather, they aim to control or relieve the symptoms of Crohn's disease with drugs and/or surgery.

Ulcerative colitis differs from Crohn's disease in that it affects only the colon (large bowel), and the inflammation is not deep but only involves the inner layer (the mucosa) of the bowel. The disease always starts in the last portion of the colon called the rectum, and may extend up from there into the rest of the colon. If it is just within the rectum, it is called ulcerative proctitis. If it has extended up further but does not involve the entire colon, it may be called left-sided ulcerative colitis. If it involves the rectum and the entire colon, it is called universal or extensive or pancolonic ulcerative colitis. Unlike Crohn's disease, in which normal-appearing areas may be interspersed with areas of inflammation, when ulcerative colitis extends up from the rectum into the colon, it does so with continuous inflammation; normal areas of bowel between the inflamed segments are not seen in ulcerative colitis. Usually, ulcerative colitis can be controlled with medication. Unlike Crohn's disease, ulcerative colitis can be completely eliminated by surgically removing the colon and rectum.

What causes IBD?

The cause of inflammatory bowel disease remains unknown. The disease is found throughout the world, more extensively in North America and northern Europe; less in central Europe, the Middle East and Australia , and least frequently in Asia and Africa . It is more predominant in temperate than in tropical climates. Whether these geographic differences have anything to do with the cause of the disease is not known. There don't seem to be any common characteristics among those who have IBD. Anyone can develop IBD, regardless of gender, race, or age. People are most frequently diagnosed with IBD between the ages of 15 to 25, or 45 to 55. There is a tendency for children and other relatives of people with IBD to develop these conditions, too. This may be for genetic reasons, or perhaps because family members often share similar environments and so may be exposed to certain conditions or substances in common.

The risk of recurring IBD

Surgery cures ulcerative colitis by removing all the diseased tissue. Surgery for Crohn's disease relieves symptoms but does not cure the disease since it may be present even in normal-appearing tissues. The recurrence rate for Crohn's disease varies, depending on which part of the intestine was affected. If both the small and large bowel were affected, the chance of the disease coming back after surgery appears to be 20 to 30% in the first year – this risk increases by 10% for each year after the procedure. If the disease is limited to the small bowel alone, the recurrence rate is slightly less. If the disease was limited to the colon, the recurrence rate is less still. The risk of recurring IBD may be lessened by medical therapy