Cumulative incidence of perianal manifestations in pediatric‐onset inflammatory bowel disease: A nationwide Swedish cohort study

Abstract

Perianal disease is a recognized complication of pediatric Crohn's disease (CD), but data on ulcerative colitis (UC) and inflammatory bowel disease unclassified (IBD‐U) are limited. We examined the occurrence of perianal disease before, at, and after diagnosis of pediatric‐onset IBD compared with matched (age, sex, and geographical region) population comparators. Using Swedish nationwide registers, we identified 3501 children with CD, 3821 with UC, and 1081 with IBD‐U diagnosed 1990 to 2019, and 81,861 matched IBD‐free individuals. The 10‐year cumulative incidence of perianal disease was 24.8% in CD, 13.4% in IBD‐U, and 7.4% in UC, compared with 1.1% in comparators. Fistula incidences were 18.1%, 7.1%, 2.9%, and 0.3%. Perianal disease was associated with subsequent diagnostic reclassification, particularly from UC and IBD‐U to CD. Perianal disease is common in pediatric CD and occurs substantially more often in UC and IBD‐U than in the general population, highlighting its clinical relevance across pediatric IBD subtypes.