Supplementary Material for: Milan Ultrasound Criteria predict relapse of ulcerative colitis in remission

Introduction
Bowel ultrasound is a non-invasive alternative to endoscopy for assessing the disease activity of ulcerative colitis; however, it is unclear whether bowel ultrasound can predict subsequent relapse from remission.
Materials and Methods
A retrospective cohort study enrolled patients with ulcerative colitis who underwent bowel ultrasound between July 2018 and July 2021 during clinical remission (patient-reported outcome-2 ≤ 1 and no rectal bleeding) for at least 3 months and were followed up for 1 year. Ultrasonographic findings (bowel wall thickness, bowel wall flow, bowel wall stratification, and enlarged lymph nodes), Milan Ultrasound Criteria, Mayo endoscopic subscore, C-reactive protein, and fecal calprotectin levels and their association with subsequent clinical relapse were assessed. Relapse was defined as rectal bleeding score ≥ 1, stool frequency score ≥ 2, or treatment intensification for symptoms.
Results
31% of the patients (18/58) relapsed within 1 year. No single ultrasonographic finding predicted relapse, whereas Milan Ultrasound Criteria > 6.2 (p = 0.019), Mayo endoscopic subscore ≥ 1 (p = 0.013), and fecal calprotectin ≥ 250 μg/g (p = 0.040) were associated with a shorter time to relapse in the log-rank test. Milan Ultrasound Criteria > 6.2 (hazard ratio 3.22; 95% confidence interval 1.14-9.08, p = 0.027) and Mayo endoscopic subscore ≥ 1 (hazard ratio 8.70; 95% confidence interval 1.11-68.1, p = 0.039) showed a higher risk of relapse according to a Cox proportional hazards model.
Discussion/Conclusion
Bowel ultrasound can predict subsequent clinical relapse from remission in patients with ulcerative colitis using the Milan Ultrasound Criteria.