Perianal Crohn's disease is associated with poor disease outcome: a nation-wide 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 two 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, ICD-9 codes and perianal procedures. RESULTS A total of 12,904 CD patients were included in an inception cohort from 2005 (2,186 [17%] pediatric-onset), providing 86,119 person-years of follow-up. Fistulizing PCD was diagnosed in 1,530 (12%) patients (574 [4%] with severe PCD). The prevalence of PCD was 7.9%, 9.4%, 10.3% and 11.6% at one, three, five and ten years from CD diagnosis, respectively. At five years, PCD patients were more likely to be hospitalized (36% in non-PCD vs 64% in PCD; p<0.001), undergo IBD-related surgeries (9% vs 38%, respectively; P<0.001) and develop anorectal cancer (1.2/10,000 person-years for non-PCD vs. 4.2/10,000 for PCD; p=0.01). 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=0.004) and surgeries (35% vs. 43%; p=0.001). CONCLUSION Despite higher utilization of immunomodulators and biologics, PCD is associated with poor disease outcomes, especially in severe PCD.