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.