Learning Curve in Intestinal Ultrasound: Advancing from Basic Skills to Advanced Competencies-Insights from the IUS IG-IBD Master Program

Background: Intestinal ultrasound (IUS) is increasingly valuable in inflammatory bowel disease (IBD) management. Objective: This study aimed to determine the learning curve for basic and advanced IUS parameters and establish the minimum number of examinations required for diagnostic proficiency. Design: We conducted a prospective, multicenter study across eight Italian tertiary IBD centers. Eight gastroenterology trainees with extensive abdominal ultrasound experience but limited IUS exposure completed standardized training comprising theoretical education, 30 supervised examinations, and 99 independent assessments. Expert sonographers independently and blindly reassessed all independent examinations using identical protocols. Interobserver agreement was quantified using Cohen's kappa coefficients across 12 predefined categories, stratified into basic (bowel wall thickness, vascularity, stratification) and advanced (fistulas, collections, strictures) findings. Results: : Following initial training, trainees demonstrated substantial baseline competency. Basic parameters achieved consistently high performance throughout the study period (κ = 0.792 to κ = 0.842), while advanced findings showed more pronounced learning curves, improving from κ = 0.728 to κ = 0.854. Small bowel dilation exhibited the steepest learning trajectory (κ = 0.674 to κ = 0.921, 36.6% improvement, P = 0.204). Sustained primary competence (κ ≥ 0.8) was achieved by 37.5-62.5% of trainees for basic parameters within 99 examinations, with bowel wall stratification proving most challenging (37.5% success rate). Conclusion: This study establishes the first comprehensive, parameter-specific learning thresholds for IUS competency in IBD. Our findings demonstrate that structured training enables basic IUS proficiency within 75-112 examinations for experienced ultrasonographers, while advanced skills require extended practice. These data represent an important step toward defining evidence-based benchmarks for IUS training, supporting the development of standardized international curricula and safe clinical implementation.