Post written by Takahiro Muramatsu, MD, PhD, from the Department of Gastroenterology, Saitama Medical University International Medical Center, Saitama, and the Department of Gastroenterology and Hepatology, Tokyo Medical University Hospital, Tokyo, and Tomoaki Tashima, MD, PhD, from the Department of Gastroenterology, Saitama Medical University International Medical Center, Saitama, Japan.

An 80-year-old man underwent piecemeal EMR for a lesion that extended into the colonic diverticulum in the ascending colon 18 months earlier. The pathological diagnosis was intramucosal carcinoma with an inconclusive horizontal margin.

Follow-up endoscopy revealed a recurrent colonic tumor (15 mm, type 0-Is) located on a post-EMR scar. Because of poor insertion and maneuverability attributable to multiple diverticula, lesion resection via over-the-scope clip (OTSC)—assisted snare polypectomy was planned. However, the lesion was not fully aspirated into the cap of the OTSC because of severe fibrosis.

Therefore, the plan was changed to resection of the lesion on the scar with underwater EMR (UEMR) and additional OTSC-assisted snare polypectomy to ensure no residual tumor on the resection surface. After we performed UEMR, a depression thought to be a diverticulum that had not been visible before resection was observed on the resection surface. Perforation also was a concern; therefore, the mucosal defect was closed rapidly with an OTSC before the next planned OTSC-assisted snare polypectomy.

Because of the possibility of a residual tumor in the diverticulum, snaring resection was performed above the clip. Pathological examination of tissue resected via UEMR indicated intramucosal carcinoma without lymphovascular invasion. The horizontal margin was diagnosed as inconclusive, and the vertical margin was diagnosed as negative. No residual tumor was observed in the lesion additionally resected via OTSC-assisted snare polypectomy.

We achieved hybrid endoscopic resection combining UEMR and OTSC-assisted snare polypectomy for a recurrent colonic tumor with a hidden diverticulum, thus avoiding surgical resection. UEMR is a method for managing lesions on a scar, but deep margins pose a challenge. The combination of UEMR and OTSC-assisted snare polypectomy enables resection of lesions with deep margins and mucosal defect closure.

Attention should be focused on the possibility of a hidden diverticulum under the scar when cases include recurrent lesions involving the diverticulum.

Endoscopic images. A, White-light image. A protruding lesion was located on a post-EMR scar of the ascending colon (diameter, 15 mm). B, Endoscopic image obtained with narrow-band imaging. C, Magnified narrow-band imaging depicted irregular microvessel and surface patterns. D, Underwater EMR (UEMR) with a preattached over-the-scope clip (OTSC). E, After we performed UEMR, a diverticulum was observed on the resection surface (green arrow). F, The diverticulum was inverted and a polyp-like elevation was detected above the clip after closure of the mucosal defect using an OTSC. The green dotted line indicates the elevation. G, The snaring resection was performed above the clip. H, After OTSC-assisted snare polypectomy, no tumor remnant was detected endoscopically.

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