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Citation: Nakayama K. Underwater endoscopic mucosal resection: An emerging Gold Standard? Jr.med.res. 2023; 6(2):2.

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Editorial

Underwater endoscopic mucosal resection: An emerging Gold Standard?

Dr. Katsura Nakayama

Department of endoscopy, Tokyo Midtown Clinic

Tokyo, Japan

中山桂

Endoscopic mucosal resection (EMR) for gastrointestinal lesions is a well-established technique associated

with considerable rate of complete resection and histopathological adequate tissue sampling. Conventional

endoscopic resection (CEMR) with submucosal injection is the standard of colorectal polypectomy [1].

First described in 2012, underwater endoscopic mucosal resection (UEMR) is a technique using water

insufflation for the resection of sessile colorectal lesions [2]. Related floating and magnification effects

contributed to better lesions delineation and improved considerably the resectability [3]. UEMR was

quickly confronted to CEMR in the management of big, flattened lesions (>30mm). Recent reports

suggested that UEMR offered better lesion visualization and most effective snares manipulation. This

technical progress might be associated with higher en-bloc R0 resection and lower piecemeal effect rates.

Furthermore, UEMR was significantly associated with shorter procedure time, lower blood loss and lower

recurrence rates [4]. With the declining of the learning curve, UEMR was introduced in the management

of duodenal, gastroesophageal and small intestinal lesions [5]. Moreover, this technique is recently

recommended as standard procedure for small colorectal polyps suspicious for high‐grade dysplasia to

avoid R1 cold snare excision of occult cancer [6].

Several techniques of lesion demarcation were included in CEMR procedure. Adjuvant submucosal

injection using saline, viscous solutions and staining dyes increased lesion delineation and reduced the

number needed of snare resections. This contributed objectively to the improvement of CEMR outcomes

either in cold or thermal ablation. Staining in the conventional technique increased the feasibility of the

resection of recurrent lesions in scarred and tricky colonic locations [7].

The urge for the comparison between CEMR and UEMR was objective. However, only few meta-analyses

of randomized controlled trials were published the past five years. Initial result showed that UEMR is a

safe and efficient alternative to CEMR. UEMR had better results for large lesions, particularly in difficult

locations like the caecum [8]. Most recent evidence suggested that colorectal UEMR results in higher en-

bloc resection and lower recurrence rates when compared to CEMR. However, both techniques may have

comparable resection times and safety profiles [9,10].

References

[1] Saito Y, Ono A. Underwater Endoscopic Mucosal Resection for Colorectal Lesions: A bridge between conventional endoscopic mucosal resection and endoscopic submucosal

dissection. Gastroenterology. 2021;161:1369-71.

[2] Garg R, Singh A, Aggarwal M, Bhalla J, Mohan BP, Burke C, et al. Underwater endoscopic mucosal resection for 10 mm or larger nonpedunculated colorectal polyps: A

systematic review and Meta-analysis. Clin Endosc. 2021;54:379-89.

[3] Yuan X, Gao H, Liu C, Cui H, Zhang Z, Xie J, et al. Effectiveness and safety of the different endoscopic resection methods for 10- to 20-mm nonpedunculated colorectal

polyps: A systematic review and pooled analysis. Saudi J Gastroenterol. 2021;27:331-41.

[4] Yamashina T, Hanaoka N, Setoyama T, Watanabe J, Banno M, Marusawa H. Efficacy of underwater endoscopic mucosal resection for nonpedunculated colorectal polyps:

A systematic review and Meta-analysis. Cureus. 2021;13:e17261.

[5] Liu J, Duan S, Wang Y, Peng H, Kong Y, Yao S. Efficacy and safety of underwater endoscopic mucosal resection for ≤20 mm superficial non-ampullary duodenal epithelial

tumors: Systematic review and meta-analysis. Front Med (Lausanne). 2023;9:1077806.

[6] Okada M, Shinozaki S, Ikeda E, Hayashi Y, Takezawa T, Fukuda H, et al. Underwater endoscopic mucosal resection of small rectal neuroendocrine tumors. Front Med

(Lausanne). 2022 ;9:835013.

[7] Li X, Zhu H, Li F, Li R, Xu H. Different endoscopic treatments for small colorectal polyps: A systematic review, pairwise, and network meta-analysis. Front Med (Lausanne).

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[8] Zhang Z, Xia Y, Cui H, Yuan X, Wang C, Xie J, et al. Underwater versus conventional endoscopic mucosal resection for small size non-pedunculated colorectal polyps: a

randomized controlled trial : (UEMR vs. CEMR for small size non-pedunculated colorectal polyps). BMC Gastroenterol. 2020;20:311.

[9] Chandan S, Bapaye J, Khan SR, Mohan BP, Ramai D, Dahiya DS, et al. Safety and efficacy of underwater versus conventional endoscopic mucosal resection for colorectal

polyps: Systematic review and meta-analysis of RCTs. Endosc Int Open. 2023;11:E768-77.

[10] Sundaram S, Seth V, Jearth V, Giri S. Underwater versus conventional endoscopic mucosal resection for sessile colorectal polyps: an updated systematic review and meta-

analysis. Rev Esp Enferm Dig. 2023;115:225-33.