Ulcerative colitis (UC) is an inflammatory bowel disease that has a worldwide distribution with an incidence of 4-7/100 000. The disease usually appears in young adults with a peak in the 30s, although UC also occurs in children and the elderly. As with Crohn's disease, UC appears to be more common in people of Jewish heritage.
The pathogenesis of ulcerative colitis is unknown.
In contrast to Crohn's disease, UC is limited to the colon and rectum, is primarily mucosal (not transmural) and is a diffuse (as opposed to segmental) process. In virtually all cases, UC involves the rectum and spreads proximally in a diffuse manner to involve just the rectum (ulcerative proctitis) or up to and including the entire colon (pancolitis). The macroscopic appearance is that of inflamed, erythematous and granular mucosa with superficial ulcers. In severe cases, inflammation can be so severe that the entire wall is inflamed giving rise to fulminant colitis with megacolon. In ulcerative colitis, the colon is able to become massively dilated with severe inflammation because the wall is not fibrosed due to prior transmural inflammation as occurs in Crohn's disease. Inflammatory polyps may also occur. Histologically, inflammation is primarily mucosal and diffuse, with prominent crypt abscesses and a lack of granulomas.
Like Crohn's disease, UC is characterized by intermittent attacks with remissions and exacerbations. Colitis may be mild with rectal bleeding, abdominal pain or fever, or in a minority of cases, can be severe or fulminant with significant bleeding, fever and a risk of intestinal perforation. Extra-intestinal manifestations are similar to those seen in Crohn's disease.
The most important complication of long-standing UC (and to a lesser extent Crohn's disease) is the development of mucosal dysplasia and adenocarcinoma. The risk of developing dysplasia and adenocarcinoma is related to the duration and extent of disease. The risk begins to increase after approximately 8-10 years and is greatest in patients with pancolitis. A recent meta-analysis (published in April 2001) of the risk of developing adenocarcinoma in chronic UC has lowered the risk compared with traditional teaching, but it is still significant, as follows: 2% at 10 years, 8% at 20 years and 18% at 30 years.
Because of the risk of cancer, patients who have had UC (particularly pancolitis) for >8-10 years should undergo periodic colonoscopy with the procurement of multiple biopsies for the pathologist to assess for dysplasia.