Blue dyes such as indigo carmine have become a frequent component of the submucosal injectate for EMR. Confirmation of the correct resection plane and assessment of the resection defect are facilitated by the selective staining of the submucosal layer. Nonstained areas are more difficult to evaluate and may contain inadvertent muscularis propria (MP) injury. The use of topical submucosal chromoendoscopy (TSC) may allow rapid and accurate assessment of these unstained areas and visual recognition of MP injury.

To evaluate the utility of a novel technique in the assessment of nonstained areas within the post-EMR defect.

Single-center prospective cohort study.

Academic, tertiary care referral center.

A total of 143 patients undergoing wide-field colonic EMR for sessile lesions 20 mm or larger.

A standard inject-and-resect EMR technique was applied with indigo carmine blue dye in the injectate. Defects with areas of nonstaining were recorded and examined, and then irrigated with the submucosal injectate by using the blunt tip of the injection catheter.

Detection of additional cases of MP injury by using TSC.

A total of 147 EMRs were performed. Focal areas of defect nonstaining were seen in 25 of cases (17%), with no MP injury identified on initial examination. After TSC, 2 additional cases of MP injury were identified, and these were successfully managed endoscopically. Intraprocedural recognition of deep resection increased from 4 cases (2.8%) to 6 cases (4.1%), thereby avoiding potential delayed perforation in 2 patients.

Single-center, nonrandomized study.

TSC is simple and effective and rapidly confirms the plane of resection and may improve detection of intraprocedural perforation.