The relationship between site of intestinal inflammation and primary sclerosing cholangitis (PSC) development in inflammatory bowel disease (IBD) has not been studied extensively, but may be important in understanding the pathogenesis of PSC. We aimed to determine patterns of disease distribution in IBD patients with and without PSC. We performed a 2-part study involving the following: (1) 2754 IBD patients and (2) 82 separate PSC patients attending the Irish National Liver Transplant Unit. Fifty-nine of 2708 (2.2%) IBD patients had PSC. In ulcerative colitis patients, PSC incidence increased with increasing colonic involvement (P = .001) and was relatively rare in those without total colitis. Thirteen Crohn's disease patients had PSC, none with isolated small-bowel disease had PSC (P = .03). In study 2, the majority of ulcerative colitis patients with PSC had total colitis, whereas the remainder had disease extending at least to the left colon. In addition, all 10 PSC patients with Crohn's disease had colonic involvement. An inflamed colon, but not small bowel, is important in PSC development and it is possible that bacterial translocation and subsequent portal bacteremia is important in PSC development in IBD.
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