Difficult-to-treat inflammatory bowel disease (DTT-IBD) represents a heterogeneous group of patients with treatment-refractory, structurally complicated, postoperative, perianal, pouch-related, or psychosocially complex disease. This multicentre ambidirectional observational cohort will establish a longitudinal registry of adults with inflammatory bowel disease and systematically identify patients meeting prespecified DTT-IBD criteria. Clinical data will be reconstructed retrospectively and collected prospectively using a common data dictionary, including disease phenotype, advanced-therapy exposure and failure, objective disease assessments, multidisciplinary decision-making, treatment implementation, surgery, hospitalization, and long-term outcomes.
The registry will characterize the occurrence, clinical domains, treatment trajectories, longitudinal disease-control states, and outcomes of DTT-IBD. No treatment, diagnostic test, dose, surgery, or monitoring procedure will be assigned by the study. Clinical management will remain entirely at the discretion of the treating physicians and patients. The platform is designed to support prespecified nested studies addressing treatment-failure mechanisms and clinical decisions, longitudinal DTT trajectories and cumulative uncontrolled disease, and implementation of multidisciplinary care.