Transabdominal ultrasonography for small-bowel lesions in Crohn’s disease: a prospective comparison with balloon-assisted enteroscopy

Background/Aims: Transabdominal ultrasonography (TUS) is increasingly used to assess small-bowel lesions in Crohn's disease (CD); however, the diagnostic performance of prospective segment-specific data relative to balloon-assisted enteroscopy (BAE) remains limited. Methods: In this prospective, single-center study, 94 patients with CD underwent TUS the day before BAE. The diagnostic accuracy of TUS for mucosal inflammation and stenosis was evaluated separately for the terminal ileum and proximal small bowel, using BAE as the reference standard and endoscopic criteria based on the Simple Endoscopic Score for Crohn's Disease. We performed exploratory analyses of clinical factors associated with TUS detectability, including multivariable logistic regression for inflammatory lesions and exploratory comparisons for stenosis. Results: For mucosal inflammation, TUS sensitivity and specificity were 69% and 94% in the terminal ileum (accuracy, 90%) and 91% and 82% in the proximal small bowel (accuracy, 84%), respectively. For stenosis, the sensitivity and specificity were 78% and 98% in the terminal ileum (accuracy, 96%) and 63% and 89% in the proximal small bowel (accuracy, 84%), respectively. In exploratory analyses of BAEconfirmed inflammatory lesions, anastomotic involvement, history of bowel resection, and small-bowel resection were associated with TUS detectability in univariate analyses. No independent predictors were identified in the multivariable logistic regression. Conclusions: Compared to BAE as the reference standard, TUS showed high specificity and segment-dependent sensitivity for detecting small-bowel inflammation and stenosis. These findings support TUS as a complementary, practiceinforming, and noninvasive assessment tool, indicating that additional evaluation may be needed when clinical suspicion persists despite negative or equivocal TUS findings.