Growth impairment in Japanese children with inflammatory bowel disease: A multicenter prospective cohort study

Objectives: To investigate the prevalence and characteristics of growth impairment (GI) in children with inflammatory bowel disease (IBD). Methods: In this prospective observational study, 402 children with ulcerative colitis (UC, n = 257) and Crohn's disease (CD, n = 145) were enrolled from the Japanese Pediatric IBD Registry (2012–2020). GI was defined by Paris classification criteria. Longitudinal outcomes were assessed in children with ≥2 years of follow-up (n = 307). Results: At diagnosis, the GI prevalence was comparable between children with UC and CD (6.2% vs. 8.3%, p = 0.54). However, children with UC diagnosed at 0–4 years demonstrated significantly higher GI rates (35.3%) than older children (p < 0.001). All children with CD experiencing GI had small intestinal lesions. Among those with GI at diagnosis, fewer children with UC (9%) recovered growth at a 2-year follow-up than those with CD (50%). Among children with normal growth at baseline, new-onset GI occurred in 23% of UC and 16% of CD cases. Of these, 31% recovered within 2 years, while persistent GI was observed in 16% of UC and 11% of CD cases. Prolonged corticosteroid use at 1 year was more frequent in UC (31% vs. 19%, p = 0.02) and was significantly associated with persistent GI. Conclusions: Distinct growth patterns exist in Japanese children with IBD. Children with UC diagnosed at 0–4 years are particularly vulnerable and may benefit from early, steroid-sparing treatment. The association between small intestinal lesions and GI in CD emphasizes the importance of small bowel evaluation. Age-specific, patient-centered growth monitoring is crucial to optimize long-term outcomes.