Risk and natural history of colonic neoplasia in patients with primary sclerosing cholangitis and ulcerative colitis.

Primary sclerosing cholangitis (PSC) has been suggested as a risk factor for the development of colorectal cancer in ulcerative colitis (UC); however, previous studies of this association have been limited by small numbers of patients with PSC or have been performed retrospectively. This study prospectively evaluates the risk and natural history of colonic tumorigenesis in patients with PSC and UC and compares it with patients with UC without PSC. Twenty patients with PSC and UC and 25 control patients with UC were followed prospectively by colonoscopic surveillance using extensive mucosal biopsy sampling. All control patients with UC had disease extending beyond the sigmoid colon of > or = 8 years' duration; patients with PSC and UC were studied regardless of disease duration. Forty-five percent (9 of 20) of the patients with PSC and UC had dysplasia compared with 16% (4 of 25) of the control patients with UC (P < or = 0.002). Prior liver transplantation did not affect the risk of colonic dysplasia. The time course for progression to dysplasia was similar between the patients with PSC and UC and the patients with UC; however, the patients with PSC and UC were five times more likely to develop dysplasia. Patients with PSC and UC represent a subset of patients with UC who are at markedly increased risk for colonic neoplasia and who need close colonoscopic surveillance with extensive biopsy sampling.