Prevalence and clinical significance of the muscle retracting sign during endoscopic submucosal dissection of large macronodular colorectal lesions (with videos)

Background and aims: The muscle retracting sign (MRS) can be present during endoscopic submucosal dissection (ESD) of macronodular colorectal lesions. The prevalence of MRS and its pathologic and clinical implications is unclear. This study evaluated the effect of MRS on the technical and clinical outcomes of ESD. Methods: All patients referred for ESD of protruding lesions or granular mixed lesions with >10 mm macronodule granular mixed laterally spreading tumors (LST-GMs) in 2 academic centers from January 2017 to October 2022 were prospectively included. Size of the macronodule was analyzed retrospectively. The primary outcome was the curative resection rate according to MRS status. Secondary outcomes were R0 resection, perforation, secondary surgery rate, and risk factors for MRS. Results: Of 694 lesions, 84 (12%) had MRS (MRS+). The curative resection rate was decreased by MRS (MRS+ 41.6% vs lesions without MRS [MRS-] 81.3%), whereas the perforation (MRS+ 22.6% vs MRS- 9.2%), submucosal cancer (MRS+ 34.9% vs MRS- 9.2%), and surgery (MRS+ 45.2% vs MRS- 6%) rates were increased. The R0 resection rate of MRS thorn colonic lesions was lower than that of rectal lesions (53% vs 74.3%). In multivariate analysis, protruding lesions (odds ratio, 2.47; 95% confidence interval, 1.27-4.80) and macronodules >4 cm (odds ratio, 4.24; 95% confi- dence interval, 2.23-8.05) were risk factors for MRS. Conclusions: MRS reduces oncologic outcomes and increases the perforation rate. Consequently, procedures in the colon should be stopped if MRS is detected, and those in the rectum should be continued due to the morbidity of alternative therapy.