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Douglas K. Rex, MD, FASGE reviewing Yen AW, et al. Gastrointest Endosc 2019 Oct 16.


Recent randomized controlled trials found that underwater endoscopic mucosal resection (UEMR) results in more en bloc resections and faster resection for flat and sessile colorectal lesions ≥20 mm in size.

The current trial randomized patients with lesions 6 to 9 mm in size to underwater cold snaring or standard cold snaring and patients with lesions ≥10 mm in size to conventional EMR (CEMR) with submucosal injection versus UEMR. 

There were no substantial differences between conventional and underwater cold snaring for 6- to 9-mm lesions, but UEMR had advantages compared to CEMR in lesions ≥10 mm, including faster resection (2.9 minutes vs 5.6 minutes) and fewer snare resections of lesions ≥20 mm (2.3 vs 3.0). There were no significant differences in residual polyp rates, complications, or as judged by four-quadrant biopsy samples of the margin, en bloc resection rates. Residual polyp and complications were very low in both groups.

These results support other recent controlled trials that have found that UEMR has similar efficacy and complication rates compared to CEMR but that UEMR is accomplished with fewer snare resections or more en bloc resections and is faster to perform than CEMR.

Note to readers: At the time we reviewed this paper, its publisher noted that it was not in final form and that subsequent changes might be made.

Douglas K. Rex, MD, FASGE


Yen AW, Leung JW, Wilson MD, Leung FW. Underwater versus conventional endoscopic resection of nondiminutive nonpedunculated colorectal lesions: a prospective randomized controlled trial (with video). Gastrointest Endosc 2019 Oct 16. (Epub ahead of print) (

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