The second section, the transverse colon , crosses the upper abdomen to the left side. The third section extends downward on the left side of the abdomen toward the pelvis and is called the descending colon . The final section is the sigmoid colon . Feces are stored in the descending and sigmoid colon until they are passed through the rectum and anus . The rectum extends through the pelvis from the end of the sigmoid colon to the anus.
Ulcerative colitis is an inflammatory disease of 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. The disease develops uniformly and consistently until, in some cases, the colon becomes rigid and foreshortened. Crohn's disease is an inflammation that extends into the deeper layers of the intestinal wall. It is found most often in the ileum and the cecum, which is sometimes referred to as the ileocecal region .