What is ulcerative colitis (UC)?

Updated: Feb 23, 2019
  • Author: Ali Nawaz Khan, MBBS, FRCS, FRCP, FRCR; Chief Editor: Eugene C Lin, MD  more...
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Answer

Answer

Ulcerative colitis (UC) is a type of inflammatory bowel disease (IBD), along with Crohn disease (CD). Unlike Crohn disease, which can affect any part of the gastrointestinal tract, ulcerative colitis characteristically involves the large bowel UC mainly affects the rectum and sigmoid colon, but it may involve the entire colon and the terminal ileum. In addition, cases with proximal involvement have been described (eg, diffuse gastritis, focally enhanced gastritis, and duodenitis). [1, 2, 3, 4]

UC is a multifactorial polygenic disease; the exact etiology is unknown. Included in the etiologic theories are environmental factors, immune dysfunction, and a likely genetic predisposition. Some have suggested that children of below-average birth weight who are born to mothers with ulcerative colitis have a greater risk of developing the disease.

Double-contrast barium enema study shows changes o Double-contrast barium enema study shows changes of early disease. Note the granular mucosa.
Single-contrast enema study in a patient with tota Single-contrast enema study in a patient with total colitis shows mucosal ulcers with a variety of shapes, including collar-button ulcers, in which undermining of the ulcers occurs, and double-tracking ulcers, in which the ulcers are longitudinally orientated.
Postevacuation image obtained after a single-contr Postevacuation image obtained after a single-contrast barium enema study shows extensive mucosal ulceration resulting from Shigella colitis.

Histocompatibility human leukocyte antigen (HLA)–B27 is identified in most patients with ulcerative colitis, though this finding is not associated with the condition. Immune dysfunction has been postulated as a cause, although the clear evidence of this is limited. Ulcerative colitis might also be linked to diet, though diet is thought to play a secondary role. Food or bacterial antigens might exert an effect on the already damaged mucosal lining, which has increased permeability.

The severity of ulcerative colitis can be graded as follows:

  • Mild — Bleeding per rectum and fewer than 4 bowel motions per day

  • Moderate — Bleeding per rectum with more than 4 bowel motions per day

  • Severe — Bleeding per rectum, more than 4 bowel motions per day, and a systemic illness with hypoalbuminemia (< 30 g/L)

Patients are defined as having extensive disease if inflammation extends proximal to the splenic flexure; left-sided disease if inflammation extends proximal to the rectum but not past the splenic flexure (or < 50 cm from the anus); and proctitis if inflammation is limited to the rectum (or < 15–20 cm from the anus). Both disease severity and anatomic extent are important in choosing appropriate treatment.


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