The Phenotypic Expression of Inflammatory Bowel Disease in Patients with Primary Sclerosing Cholangitis Differs in the Distribution of Colitis

Background Inflammatory bowel disease (IBD) associated with primary sclerosing cholangitis (PSC) is reported to be mild and prone to right-side predominance with rectal sparing. However, no dedicated studies evaluating patterns of presentation of liver disease with respect to IBD are available. Methods We performed a detailed histological examination of the colonic biopsies in the context of PSC, identifying 97 patients [89 with ulcerative colitis and ten with Crohn's disease (CD)] stratified into two groups, based on their initial disease presentation: hepatic/biliary (group 1-PSC-IBD; n = 56) versus colonic (group 2-IBD-PSC; n = 41). Results Inflammatory bowel disease that preceded PSC had a tendency to have a pan-colitis'' distribution; this group included all patients with CD. Inflammatory bowel disease diagnosis that followed PSC presentation was more likely to be right-sided, sparing the descending, sigmoid and rectal regions (p = 0.002). In both groups, colitis was mild with focal deep plasmacytosis and occasional mild cryptitis. Active cryptitis with crypt abscesses, surface erosion and ulceration were not identified in any of the patients. Conclusion Colitis associated with PSC shows mild disease activity and the colitis pattern is associated with disease presentation, i.e. colitis preceding PSC (IBD-PSC cohort) typically have a pancolitic distribution, while colitis following PSC (PSC-IBD cohort) demonstrates right-sided predominance. Awareness by pathologists and clinicians of these patterns of inflammatory bowel disease is important and of use in directing appropriate investigations for patients.