Superior predictive value of transmural over endoscopic severity for colectomy risk in ulcerative colitis: a multicenter prospective cohort study

Background and aims: Endoscopic activity is associated with an increased risk of surgery in patients with ulcerative colitis (UC). Transmural activity, as defined by Milan Ultrasound Criteria (MUC) >6.2, reliably detects endoscopic activity in patients with UC. The study aimed to assess in UC patients whether transmural severity is a better predictor of colectomy as compared to endoscopy. Methods: Consecutive adult UC patients were recruited in two IBD Referral Centers and underwent colonoscopy and intestinal ultrasound in a blinded fashion. The need for colectomy was assessed at follow-up. Univariable and multivariable logistic and Cox regression analyses were performed. ROC analysis was used to compare MUC baseline values and Mayo Endoscopic Scores (MES) in predicting colectomy risk. Results: Overall, 141 patients were enrolled, and 13 underwent colectomy in the follow-up period. Both MES (HR: 3.15, 95% CI: 1.18-8.37, p=0.02) and MUC (HR: 1.48, 95% CI: 1.19-1.76, p <0.001) were associated with colectomy risk, but only MUC was independently associated with this event at multivariable analysis (HR: 1.46, 95% CI: 1.06-2.02, p=0.02). MUC was the only independent variable associated with colectomy risk in patients with clinically active disease, OR: 1.53 (1.03-2.27) P=0.03. MUC demonstrated higher accuracy than MES (AUROC 0.83, 95% CI: 0.75-0.92 vs. 0.71 95% CI: 0.62-0.80) and better performance for predicting colectomy (p=0.02). The optimal MUC score cut-off value for predicting colectomy, as assessed by the Youden index, was 7.7. Conclusions: A superior predictive value was found for transmural versus endoscopic severity for colectomy risk in UC patients.