The relation between inflammatory bowel disease (IBD), mainly ulcerative colitis, and primary sclerosing cholangitis (PSC) is particularly close, as approximately two thirds of patients with PSC have, or will develop, ulcerative colitis, and PSC occurs in approximately 3–7% of patients with ulcerative colitis. In a large Swedish epidemiological study, approximately 5.5% of patients with extensive colitis had PSC.1 Despite the close relation the aetiology of both diseases is unknown.

It is well established that patients with ulcerative colitis have an increased risk of developing colorectal carcinoma. The two major risk factors that have been identified in the development of neoplasia are duration of disease and the extent of colitis. Additional risk factors have been described such as the presence of colonic epithelial cell dysplasia and early onset of colitis. It has been suggested that pharmacological treatment for ulcerative colitis may reduce the risk of colorectal cancer.2

Recently, the presence of PSC has been suggested to increase the risk of dysplasia and colorectal cancer in patients with ulcerative colitis.3 In the initial reports from Sweden the absolute cumulative risk of developing colorectal dysplasia/carcinoma in the PSC/ulcerative colitis group was 9%, 31% and 50%, respectively after 10, 20 and 25 years of disease duration. In the …