Evaluating sonographic response and remission in inflammatory bowel disease: aligning intestinal ultrasound assessment with STRIDE-II timelines.

BACKGROUND AND AIMS: The diagnostic accuracy of intestinal ultrasound (IUS) is established; however, guidance on the timing and interpretation of sonographic response and remission in inflammatory bowel disease (IBD) remains limited. This review synthesizes current evidence to define expected response and remission kinetics in Crohn's disease (CD) and ulcerative colitis (UC) across STRIDE-II aligned reassessment timepoints. METHODS: A structured narrative review was undertaken of studies published up to August 31, 2025 evaluating longitudinal IUS changes following initiation of medical therapy in patients with CD and UC. Outcomes were synthesized across early (<3 months), intermediate (3-6 months), and longer-term (6-12 months) reassessment intervals aligned with STRIDE-II timelines. RESULTS: In CD, sonographic response was reported in approximately 51%-66% of patients by 12 weeks, while remission was reported in 14%-37%. At 3-6 months, response was reported in approximately 36%-38%, while remission was reported in 12%-38%. Longer-term response and remission were reported in approximately 36%-57% and 24%-42%, respectively, at 48-56 weeks. In UC, response was reported in 57%-77% and remission in 45%-64% by weeks 8-12 in selected cohorts. However, traditional IUS response and remission estimates beyond this early treatment phase remain limited in UC. Direct comparisons between studies was limited by heterogeneity in outcome definitions, reassessment timepoints, therapy class, and disease characteristics. CONCLUSION: IUS is a practical, non-invasive tool for monitoring therapeutic response in IBD. The optimal timing of reassessment is likely to vary according to therapy-specific time to response, IBD subtype, disease phenotype, and bowel segment. Standardization of definitions and reassessment timelines remain central to integrating IUS into treat-to-target models of IBD care.