Wall Thickness Ratio—A New Magnetic Resonance Parameter—Is Associated With the Outcome of Biological Therapy in Patients With Ileal and Ileocolonic Crohn’s Disease

The present study was aimed at identifying a new magnetic resonance enterography (MRE) parameter assessing the clinical outcome of biological therapy in patients with active ileal/ileocolonic Crohn's disease (CD).Transmural healing (TH) has been associated with improved outcomes in CD. However, some patients with clinical remission and inactive disease at endoscopy do not achieve TH.Ileal/ileocolonic CD patients scheduled for biological therapy were prospectively evaluated, at baseline (T0) and after 1 year of treatment (T1), with Harvey Bradshaw Index score, blood tests, ileocolonscopy, and MRE. Clinical activity was assessed after 2 years of treatment (T2). Wall thickness ratio (WTR) was calculated in the same affected ileal segment, as the ratio between the ileum wall thickness value at T1 and the ileum wall thickness value at T0.A total of 103 patients were included. Mean WTR at T1 in nonresponders was significantly higher than in responders. At receiver operating characteristic analysis, WTR values were significantly associated to biological therapy responsiveness. A WTR cutoff value of 0.77 mm was identified to discriminate responders from nonresponders (sensitivity: 79%; specificity: 67%). In responders, the proportion of patients with a WTR<0.77 was significantly higher than the proportion of patients achieving TH at T1. Among patients achieving endoscopic remission, 11/29 (37.9%) presented TH, while 20/29 (68.9%) presented WTR<0.77 ( P : 0.035). At multivariate logistic regression analysis, WTR<0.77 was significantly associated to biological therapy response.WTR index represents an easy-to-calculate MRE parameter and seems to be a promising tool for monitoring therapeutic response in CD patients during biological therapy.