Perianal Crohn's Disease Is Associated With Poor Disease Outcome: A Nationwide Study From the epiIIRN Cohort

Background & Aims: Limited population-based data have explored perianal involvement in Crohn's disease (CD) and compared the disease course between severe and non-severe perianal CD (PCD). We aimed to explore the disease course of these phenotypes in a population-based study of CD. Methods: Cases were identified from the epi-IIRN cohort and included 2 Israeli health maintenance organizations covering 78% of the population. We validated specific algorithms to identify fistulizing PCD and to differentiate severe from non-severe disease by medication utilization, International Classification of Disease, 9th Revision codes, and perianal procedures. Results: A total of 12,904 CD patients were included in an inception cohort from 2005 (2186 pediatric-onset, 17%) providing 86,119 person-years of follow-up. Fistulizing PCD was diagnosed in 1530 patients (12%) (574 with severe PCD, 4%). The prevalence of PCD was 7.9%, 9.4%, 10.3%, and 11.6% at 1, 3, 5, and 10 years from CD diagnosis, respectively. At 5 years, PCD patients were more likely to be hospitalized (36% in non-PCD vs 64% in PCD; P < .001), undergo inflammatory bowel disease–related surgeries (9% vs 38%, respectively; P < .001), and develop anorectal cancer (1.2/10,000 person-years for non-PCD vs 4.2/10,000 for PCD; P = .01). Severe PCD was associated with poorer outcomes compared with non-severe PCD, as shown for hospitalizations (61% in non-severe PCD vs 73% in severe; P = .004) and surgeries (35% vs 43%; P = .001). Conclusions: Despite higher utilization of immunomodulators and biologics, PCD is associated with poor disease outcomes, especially in severe PCD.