Transmural healing in ulcerative colitis patients improves long-term outcomes compared to endoscopic healing alone

Background & Aims Endoscopic healing (EH) is recognized as a long-term treatment goal for patients with ulcerative colitis (UC). We investigated whether transmural healing (TH) in UC as assessed by intestinal ultrasound (IUS) is associated with improved outcomes compared to EH alone. Methods We performed a retrospective study in a tertiary center on patients with left-sided or extensive UC on stable maintenance treatment who had EH (Mayo Endoscopic Subscore [MES] ≤1) and an IUS performed within six months of an endoscopy with no treatment alterations between IUS and endoscopy. TH was defined as bowel wall thickness (BWT) < 3 mm. The primary outcome was relapse-free survival in patients with and without TH. Results A total of 61 patients (MES 0: 44.3%; MES 1: 55.7%) with a median follow up of 20 months were included. On IUS 72% of patients had TH. Twenty-three patients had a relapse (first-year relapse risk: TH: 7.5% vs no TH: 29.4%, p = 0.004; MES 0: 3.7% vs MES 1: 20.8%, P = 0.059). In multivariate Cox regression, female gender (hazard ratio [HR], 2.63; 95% CI, 1.05-6.58; P = 0.039), ≥ 2 previous advance therapies (HR, 4.06; 95% CI 1.08-15.28; P = 0.038) and non-TH (HR, 3.99; 95% CI 1.31-12.20; P = 0.015) were associated with a relapse whereas EH level (MES 0 vs MES 1) was not an associated factor (HR, 1.06; 95% CI 0.32-3.55; P = 0.924) Conclusions In UC patients TH is associated with lower relapse risk compared to EH alone. These findings imply that IUS is a non-invasive, low-cost alternative to endoscopy for stratifying UC patients for risk of relapse.