P0527 Bowel Ultrasound Scan (BUS) in Pediatric Acute Severe Colitis (ASC): a multicenter prospective study on behalf of the IBD Porto group

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Abstract Background Acute severe colitis (ASC) is a potentially life-threatening event. Optimal timing for second-line treatment in children is mainly based on the clinical score Pediatric Ulcerative Colitis Activity Index (PUCAI) score. The aim of our study was to evaluate the potential role of bowel ultrasound scan (BUS) in predicting short-term treatment outcomes in pediatric ASC. Methods This was a prospective longitudinal study, conducted across ten European centers between March 2020 and March 2024. Biologic-naïve children with Ulcerative Colitis hospitalized for ASC, either at diagnosis or at disease relapse, were included. Each patient underwent two BUS, the first one within the first 48 hours of from IVCS intravenous corticosteroids administration and the second one within 5-7 days from treatment initiation. Key metrics assessed included colonic wall thickness (CWT), colonic wall stratification (CWS) and colonic wall blood flow via power Doppler. All the above-mentioned ultrasound parameters were recorded in 4 different segments of the bowel: ascending, transverse, descending, and sigmoid colon. Furthermore, Milan ultrasound criteria (MUC) score was also calculated for each colonic quadrant. Clinical, laboratory, and treatment data were gathered during hospitalization and at 2-, 4-, and 8-weeks follow-up. Results 59 patients (61% males, median age at ASC: 14.2 years) were included. Almost 60% of patients had pancolitis, 22 (37.3%) experienced ASC at disease onset. Table 1. summarizes patients’ characteristics at ASC. 38 (64.4%) patients failed to respond intravenous corticosteroids (IVCS) and required second-line therapy with infliximab (IFX). Patients who required step-up treatment with IFX had higher colonic wall thickness (CWT) and more frequently an increased vascularization (Limberg score > 2) (p=0.041 and p=0.005, respectively). Furthermore, patients who failed to respond to IVCS and required escalation to IFX had a higher MUC score at firs BUS (p=0.042). Ten patients (16.9%) failed to respond to medical treatment and required short-term colectomy (within 8 weeks of follow-up). Patients who required colectomy had a higher CWT both at first and at second BUS (p=0.033 and p=0.004, respectively). Moreover, patients who responded to medical therapy had higher DeltaCWT (difference between worse CWT at first and at second BUS) compared to those who required surgery (p=0.0018). Conclusion BUS may serve as an effective noninvasive tool to predict first-line therapy failure and the need for colectomy in patients with ASC. Its implementation in clinical practice may enable physician to support clinical evaluation and tailor treatment escalation upon patient’s individual characteristics.