Primary sclerosing cholangitis is associated with a distinct phenotype of inflammatory bowel disease.

BACKGROUND: Primary sclerosing cholangitis (PSC) is strongly associated with inflammatory bowel disease (IBD). The aim of this study was to assess the IBD phenotype associated with PSC in a large well-phenotyped population-based PSC cohort using endoscopic and histopathologic criteria. METHODS: PSC cases were identified and ascertained, fulfilling well-established criteria, in 39 hospitals in a geographically defined region of The Netherlands. IBD location was recorded according to the Montreal Classification. As this classification does not consider segmental inflammation, backwash ileitis, or rectal sparing, an additional subgroup analysis was performed in 80 cases and 80 age- and sex-matched IBD controls, reviewing all endoscopy and pathology reports filed between 2000 and 2010. RESULTS: In all, 380 (66%) of a total of 579 PSC patients had coexistent IBD, mainly ulcerative colitis (UC) (75%). Overall, 207 (83%) of the PSC-UC patients had a pancolitis, 32 (13%) a left-sided colitis, and 9 (4%) a proctitis only. Seventy (95%) PSC-Crohn's disease (CD) patients had an (ileo)colitis and four (5%) ileitis only. In the subgroup analysis 53 (66%) PSC-UC patients were identified, 24 (30%) PSC-CD patients, and three (4%) PSC-IBD-U patients. Fifty (94%) PSC-UC patients had a pancolitis, compared with 32 (62%) matched UC patients (P < 0.001). Left-sided colitis was seen in 16 (31%) UC controls and in one PSC-UC patient (P < 0.001). Backwash ileitis and rectal sparing were rare findings (<10%) in the cohorts under study. CONCLUSIONS: IBD in PSC patients represents a distinct phenotype in that pancolitis is observed in 94% of PSC-UC and colitis in 96% of PSC-CD patients. Backwash ileitis and rectal sparing were rare findings in the PSC-UC patients.