BACKGROUND: Transmural healing (TMH) indicates resolution of inflammation in all bowel wall layers and is an emerging therapeutic target in Crohn's disease (CD). Standardized sonographic criteria for TMH and early improvement, termed Transmural Response (TMR), have not been established. This systematic review synthesizes published definitions to provide an up-to-date overview of the current evidence base for intestinal ultrasound (IUS)-based assessment in CD. METHODS: This systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Comprehensive searches of databases identified full-text articles that pre-specified TMH, TMR or normal/abnormal bowel on trans-abdominal IUS in pediatric or adult participants with CD. Definitions were summarized descriptively. RESULTS: Eighty-three full-text studies (8033 patients) met eligibility criteria; 39 (47%) defined TMH and 22 (27%) defined TMR. TMH definitions most often included bowel-wall thickness (BWT) ≤ 3mm (31/39, 79%), absent or minimal Doppler flow (25/39, 64%), and preserved bowel wall stratification (10/39, 26%). All TMR definitions required BWT reduction, but thresholds varied (absolute ≥ 1 mm or relative ≥ 25% in 16/22, 73%). Nine studies (9/22, 41%) also required Doppler flow improvement and 4/22 (18%) included additional criteria. Pediatric-specific criteria were reported in 2 TMH and one TMR studies, extrapolating from adult BWT values. Heterogeneity precluded quantitative pooling. CONCLUSIONS: Standardized IUS definitions of TMH and TMR in CD are lacking. Consistent, validated criteria are essential to enable reproducible ultrasound endpoints, support treat-to-target strategies, and facilitate incorporation of IUS into CD clinical trials and routine care.
St-Pierre et al. (Fri,) studied this question.