Ratio of submucosal thickness to total bowel wall thickness as a new sonographic parameter to estimate endoscopic remission of ulcerative colitis

Background The development of feasible, reliable parameters and criteria for intestinal ultrasound (IUS) to estimate endoscopic remission of ulcerative colitis (UC) is a crucial clinical challenge. Such parameters must be simple, objective, and reproducible so that IUS can be widely used in daily practice. We developed a new parameter called the submucosa index (SMI), defined as a percentage of the submucosal thickness (SMT) in the total bowel wall thickness (BWT), and investigated its clinical potential. Methods The inclusion criteria were performance of both IUS and endoscopy (sigmoidoscopy or colonoscopy) for UC and a ≤ 15-day time interval between IUS and endoscopy. Loss of stratification was defined as inability to identify the submucosa even with a BWT of > 3 mm. The vascularity of the colon was assessed by the modified Limberg score (mLS) and evaluated as bowel wall flow (BWF) ( −) or ( +) using color Doppler mode. A Mayo endoscopic subscore (MES) of 0 or 1 was defined as endoscopic remission. Results Seventy-four colonic segments were analyzed. The SMI, mLS, and BWF could distinguish an MES of 1 versus 2 ( p < 0.05, p < 0.01, and adjusted p < 0.001, respectively). The criteria using the BWT and SMI and using the BWT and BWF had the same estimating ability for endoscopic remission (sensitivity, 70.0%; specificity, 97.7%; positive predictive value, 95.5%; and negative predictive value, 82.7%). Conclusion The SMI is a practical, quantitative parameter based on the bowel wall structure and may be used to estimate endoscopic remission of UC.