International consensus on the use of intestinal ultrasound in inflammatory bowel disease trials

Background and Aims: Intestinal ultrasound (IUS) is increasingly used to monitor treatment efficacy in inflammatory bowel disease (IBD) trials. However, standardized definitions for response, remission, and optimal assessment timing remain undefined. An international expert consensus meeting was held to establish IUS endpoints for clinical trials. Methods: A panel of 35 international gastroenterologists and radiologists participated in a modified Delphi process, reviewing the literature and developing consensus statements. Agreement was defined as at least 75% consensus. Results: Consensus was reached on 150 statements across four domains: general IBD (30 statements), luminal Crohn’s disease (CD) (43), perianal CD (51), and ulcerative colitis (UC) (26). For luminal CD and UC, ultrasound response was defined by: (1) a ≥25% reduction in bowel wall thickness (BWT) from baseline, or (2) multifactorial improvement, combining BWT reduction with ≥1 grade decrease in color Doppler signal (CDS) or another IUS parameter. Assessments were set at weeks 4-8 for the colon and week 12 for the terminal ileum. Ultrasound remission in luminal CD was defined as: (1) BWT normalization (≤3mm) or (2) normalization of multiple parameters, including BWT, CDS, and all other IUS parameters. Similar remission criteria were proposed for UC, but the sigmoid BWT normal range (3-4mm) remained uncertain. The bowel ultrasound score (BUSS) for CD and the Milan ultrasound criteria (MUC) for UC were supported as standardized scoring systems for trials. Conclusion: This consensus provides standardized IUS definitions to enhance consistency in IBD trials, supporting the integration of IUS in future research.