Patients with ulcerative colitis usually have an intermittent course, with periods of disease inactivity alternating with "flares" of disease. Patients with proctitis or left-sided colitis usually have a more benign course: only 15% progress proximally with their disease, and up to 20% can have sustained remission in the absence of any therapy. Patients with more extensive disease are less likely to sustain remission, but the rate of remission is independent of the severity of disease.
There is a significantly increased risk of colorectal cancer in patients with ulcerative colitis after 10 years if involvement is beyond the splenic flexure. Those with only proctitis or rectosigmoiditis usually have no increased risk. It is recommended that patients have screening colonoscopies with random biopsies to look for dysplasia after eight years of disease activity.
Ulcerative colitis has a significant association with primary sclerosing cholangitis (PSC), a progressive inflammatory disorder of small and large bile ducts. As many as 5% of patients with ulcerative colitis may progress to develop primary sclerosing cholangitis.
The effect of ulcerative colitis on mortality is unclear, but it is thought that the disease primarily affects quality of life, and not lifespan.
