Comparative performance of intestinal ultrasound activity indices in pediatric ulcerative colitis: a prospective study

Background & Aims: Endoscopic assessment of disease activity in pediatric ulcerative colitis (UC) is invasive and burdensome. Intestinal ultrasound (IUS) represents a promising noninvasive alternative, but comparative data on IUS-based activity indices in children remain limited. This study evaluated the accuracy of 3 IUS activity indices, the Milan Ultrasound Criteria (MUC), the Ulcerative Colitis–Intestinal Ultrasound (UC-IUS) index, and the Civitelli index, for detecting moderate-to-severe endoscopic activity in pediatric UC and explored the added value of fecal calprotectin (FC) and the Pediatric Ulcerative Colitis Activity Index (PUCAI). Methods: In this prospective bicentric study, 75 pediatric patients with UC underwent IUS within 7 days of colonoscopy. Moderate-to-severe endoscopic activity was defined as Mayo Endoscopic Subscore (MES) ≥ 2. Diagnostic accuracy was assessed using receiver operating characteristic analysis. Results: Moderate-to-severe endoscopic activity was present in 73.3% of patients. All IUS indices significantly discriminated moderate-to-severe from no-to-mild disease (P < .001), with comparable performance (AUC 0.80 [0.68-0.92] for MUC, 0.79 [0.66-0.93] for UC-IUS, and 0.76 [0.62-0.90] for Civitelli). Bowel wall thickness (BWT) alone showed similar accuracy (AUC 0.80 [0.68-0.91]). Models combining IUS indices with FC or PUCAI yielded higher AUC (0.83 and 0.87, respectively), although differences were not statistically significant. Accuracy was highest in severe disease (MES = 3). Conclusions: MUC, UC-IUS, and Civitelli demonstrated comparable accuracy for detecting moderate-to-severe endoscopic activity in pediatric UC. BWT alone performed similarly to composite indices. Combining IUS with FC or PUCAI may provide modest additional diagnostic value, supporting a multimodal, noninvasive approach for disease monitoring and treat-to-target strategies.