There is no definitive diagnostic test for ulcerative colitis, although findings on biopsy and barium x-rays, as well as appearance during endoscopy enable a clear diagnosis in most cases. A doctor will diagnose ulcerative colitis based on medical history and physical examination, and the results of laboratory and endoscopic tests.
- Blood tests are used for various purposes, including to determine the presence of anemia (low red blood cell count). An increased number of white blood cells or elevated levels of inflammatory markers such as C-reactive protein may indicate the presence of inflammation.
- A stool sample may be taken and examined for blood, infectious organisms, or both.
Flexible Sigmoidoscopy and Colonoscopy. Flexible sigmoidoscopy and colonoscopy are standard endoscopic procedures for diagnosing ulcerative colitis. They are important in the diagnosis of both ulcerative colitis and Crohn's disease. Both procedures involve snaking a fiber-optic tube called an endoscope through the rectum to view the lining of the colon. The doctor may also insert instruments through the endoscope to remove a tissue sample for a biopsy.
- Sigmoidoscopy, which is used to examine the rectum and left (sigmoid) colon, lasts about 10 minutes and is done without sedation. It may be mildly uncomfortable, but it is not painful. Ulcerative colitis almost always involves the lower left colon and rectum. The doctor usually observes an evenly distributed inflamed surface lining the intestine, and the bowel wall bleeds easily when touched with a swab. If sigmoidoscopy indicates ulcerative colitis, the doctor may order a colonoscopy to confirm the diagnosis and to identify how much of the colon is involved.
- Colonoscopy allows a view of the entire colon and requires a sedative, but it is still a painless procedure performed on an outpatient basis. It is helpful for distinguishing between Crohn's disease and ulcerative colitis and in screening for colon cancer.
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.