Introduction

Inflammatory bowel disease (IBD) is a general term that includes two main disorders:

• Ulcerative colitis
• Crohn's disease

These two diseases are related, but they are considered separate disorders with somewhat different treatment options. The basic distinctions are location and severity. As many as 10% of patients with IBD have features and symptoms that match the criteria for both disorders, at least in the early stages. (This is called indeterminate colitis.)

Ulcerative Colitis. Ulcerative colitis occurs only in the large intestine. Ulcers form in the inner lining, or mucosa, of the colon or rectum, often resulting in diarrhea, which may be accompanied by blood and pus. The inflammation is usually most severe in the sigmoid and rectum and usually diminishes higher in the colon. It is divided into divided into different categories depending on the location of the disease. The three main types of ulcerative colitis are:

Click the icon to see an image of the structure of the colon.

• Proctitis. Disease only in the rectum (the lower part of the colon that connects with the anus). In about a third of patients, ulcerative colitis begins with ulcerative proctitis.
• Limited or Distal Colitis. Disease in the left side of the colon.
• Pancolitis. Disease in entire colon.

Click the icon to see an image of the types of ulcerative colitis.

Crohn's Disease. Crohn's disease is an inflammation that extends into the deeper layers of the intestinal wall. It is found most often in the area bridging the small and large intestines, specifically in the ileum and the cecum, which is sometimes referred to as the ileocecal region. Less often, Crohn's disease occurs in other parts of the gastrointestinal tract, including the anus, stomach, esophagus, and even the mouth. It may affect the entire colon, form a string of connected ulcers in one part of the colon, or develop as multiple scattered clusters of ulcers skipping healthy tissue in between. [For more information, see In-Depth Report #103: Crohn's disease.]

The Gastrointestinal Tract

The gastrointestinal (GI) tract (the digestive system) is a tube that extends from the mouth to the anus. It is a complex organ system that first carries food from the mouth down the esophagus to the stomach and then through the small and large intestine to be excreted through the rectum and anus.

Esophagus. The esophagus, commonly called the food pipe, is a narrow muscular tube, about 9 1/2 inches long that begins below the tongue and ends at the stomach.

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Review Date: 09/28/2010
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org)