The inflammatory bowel diseases (IBD) are Crohn's disease (CD) and ulcerative colitis (UC). The intestinal complications of Crohn's disease and ulcerative colitis differ because of the characteristically dissimilar behaviors of the intestinal inflammation in these two diseases. <br>The intestinal complications of IBD are caused by intestinal inflammation that is severe, widespread, chronic, and/or extends beyond the inner lining (mucosa) of the intestines. <br>While ulcerative colitis involves only the large intestine (colon), Crohn's disease occurs throughout the gastrointestinal tract, although most commonly in the lower part of the small intestine (ileum). <br>Intestinal ulceration and bleeding are complications of severe mucosal inflammation in both ulcerative colitis and Crohn's disease. <br>Intestinal inflammation in Crohn's disease involves the entire thickness of the bowel wall, whereas the inflammation in ulcerative colitis is confined to the inner lining. Accordingly, complications such as intestinal strictures, fistulas, and fissures are far more common in Crohn's disease than in ulcerative colitis. <br>Intestinal strictures and fistulas do not always cause symptoms. Strictures, therefore, may not require treatment unless they cause significant intestinal blockage. Likewise, fistulas may not require treatment unless they cause significant abdominal pain, infection, external drainage, or bypass of intestinal segments. <br>