Introduction

Introduction

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

• Ulcerative colitis
• Crohn's disease

Some evidence suggests that they are part of a biologic continuum, but at this time they are considered distinct disorders with somewhat different treatment options. The basic distinctions are location and severity. As many as 10% of patients with IBD have findings and symptoms that match the criteria for both disorders, at least in the early stages (which 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, blood, and pus. The inflammation is usually most severe in the sigmoid and rectum and usually diminishes higher in the colon. It is sometimes divided into one of four categories depending on the location of the disease:

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

• Proctitis. Disease only in the rectum (the lowest part of the large intestine that connects with the anus). Constitutes about 30% of cases.
• Proctosigmoiditis. Disease in the rectum and sigmoid (the next portion of the intestine leading up from the rectum). Constitutes about 30% of cases.
• Left-Sided Colitis. Disease in the left side of the large intestine. Constitutes about 40% of cases.
• Pancolitis. Disease in entire colon. Very uncommon.

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

In most patients the location of the disease does not change, but as many as 30% of patients with proctitis or proctosigmoiditis will experience some progression.

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. Crohn's disease less frequently 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 contiguous 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.]