Since the risk of dysplasia or cancer increases with the duration of ulcerative colitis, testing should be done more frequently as duration of disease increases. One method calls for testing every three years for the first 15 years of disease, every two years for the next 10 years, and every year thereafter. Such an approach provides for at least 20 examinations in 40 years of disease. Most of the evaluations would be performed in the later years when the risk is the highest.

A history of primary sclerosing cholangitis, a liver disease associated with ulcerative colitis, adds significantly to the already high risk of dysplasia and colorectal cancer in patients with ulcerative colitis. Therefore, at the same duration of disease, patients with primary sclerosing cholangitis should be tested more often, perhaps every year. For these patients, prophylactic colectomy may offer the best alternative in terms of life expectancy.

Because dysplasia can be present focally as well as diffusely, biopsies must be taken throughout the colon. The sensitivity of testing for detecting dysplasia is increased with a greater number of biopsies taken. At least 32 biopsies should be taken of flat mucosa and of raised lesions. 

Any biopsy that is positive for dysplasia poses an inordinately high risk of colorectal cancer; the risk of concurrent cancer has been reported to be as high as 19 percent in patients with low-grade dysplasia and 42 percent in patients with high-grade dysplasia. Therefore, a total proctocolectomy is usually recommended for all patients with low-grade dysplasia, high-grade dysplasia or cancers found at colonoscopy.

Research is ongoing to determine whether alternative markers of malignancy or improved visualization of the colon with chromoendoscopy, narrow band imaging, or autofluorescence can significantly improve the sensitivity of the present surveillance techniques to detect dysplasia.