Transition Failure in Pediatric Inflammatory Bowel Disease: An Underrecognized Determinant of Long-Term Outcomes.

Background/Objectives: The transition from paediatric to adult care in inflammatory bowel disease (IBD) is a period of genuine clinical vulnerability. Despite international guidelines, real-world implementation of transition programmes remains inconsistent and the field lacks consensus on clinically meaningful outcome measures. We introduce the concept of "transition failure" as a provisional composite outcome framework to reorient research toward patient-centred endpoints. Methods: A narrative search of PubMed, MEDLINE, and Embase was conducted using terms including "inflammatory bowel disease", "transition", "transfer to adult care", and "adherence"; no formal quality appraisal was applied. The search covered the databases from inception to 30 June 2026. Results: We synthesise current evidence on transition readiness and its limitations, delineate patient- and system-level barriers-including the underappreciated role of parental involvement-and characterise high-risk subgroups. Five evidence-informed, provisional domains of transition failure are proposed. Where published data permit, illustrative quantitative benchmarks are described; however, these are not assumed to be universally applicable across therapies or disease phenotypes. A composite of ≥2 domains within 24 months is proposed as a candidate research classification rule pending prospective validation, rather than as a clinical diagnostic threshold. Conclusions: The transition failure framework provides a hypothesis-generating construct for evaluating transition quality. Prospective multicentre validation, standardised and therapy-specific outcome definitions, adjustment for baseline disease severity, and risk-stratified multidisciplinary programmes are identified as research priorities.