Diagnosis of Ulcerative Colitis (UC)

Diagnosis of ulcerative colitis involves a thorough physical examination, a medical and family history, laboratory tests (e.g., blood tests), and imaging procedures (e.g., colonoscopy).

Patients who experience abdominal pain, blood in the stool, diarrhea that does not respond to over-the-counter remedies or unexplained fever lasting more than a day or two should see a health care provider to rule out other causes and pinpoint a diagnosis of ulcerative colitis.

Laboratory tests that may be performed include the following:

  • Blood tests (used to detect anemia, which can indicate bleeding in the GI tract, or an elevated white blood cell count, which can indicate inflammation)
  • Stool samples (detect the presence of bacteria, viruses, or parasites, which may be responsible for symptoms, or detect a high white blood cell count, which can indicate inflammation)

Imaging tests used to diagnose ulcerative colitis include the following:

  • Colonoscopy is the most accurate means of diagnosing ulcerative colitis. In this test, the entire colon can be evaluated, and samples of tissue can be removed for microscopic examination (biopsy). Colonoscopy also can be used to rule out other diseases, such as Crohn's disease, diverticular disease, and colorectal cancer. There is a slight risk for perforation (tear) of the colon or excessive bleeding with this procedure.
  • Flexible sigmoidoscopy is similar to colonoscopy, except that the physician only is able to examine the lower part of the large bowel (i.e., the rectum through the descending colon [sigmoid colon]). This test, which is less comprehensive than colonoscopy, may be used when proctosigmoiditis or ulcerative proctitis (types of colitis) are suspected. Tissue samples also can be removed during sigmoidoscopy. This procedure also carries a small risk for bleeding and perforation of the colon.
  • Barium enema and barium x-ray, also called lower GI series, are less accurate tests than colonoscopy for diagnosing ulcerative colitis. These tests does not allow tissue sampling, and are not used to diagnose moderate-to-severe colitis. Lower GI series may be used to distinguish between Crohn's disease and ulcerative colitis.
  • Computed tomography (CT scan), also called computerized axial tomography (CAT) scan, may be used to help diagnose ulcerative colitis. In this procedure, x-rays of the GI tract are taken from many different angles and processed through a computer to produce three-dimensional (3-D) images. In some cases, the patient drinks an oral contrast solution prior to CT scan to provide clearer images.

Publication Review By: Stanley J. Swierzewski, III, M.D.

Published: 04 Mar 2008

Last Modified: 04 Sep 2015