Underwater endoscopic mucosal resection for colorectal lesions: Can it be an "Underwater" revolution?

Abstract

Underwater endoscopic mucosal resection (UEMR) is a newly developed technique for the removal of colorectal, duodenal, esophageal, gastric, ampullary, and small intestinal lesions. We performed a PubMed literature search for articles reporting UEMR outcomes for colorectal polyps. Four randomized controlled trials, nine non-randomized prospective trials, 16 retrospective studies, and 27 case reports were selected for assessment of the efficacy and safety of UEMR. We summarized the therapeutic outcomes of UEMR in each category according to the lesion characteristics [small size (<10 mm), intermediate size (10-19 mm), large size (≥20 mm), recurrent lesion, and rectal neuroendocrine tumor], and calculated the incidence of adverse events among the included articles. As the treatment outcomes for small polyps appeared similar between UEMR and conventional endoscopic mucosal resection (CEMR), UEMR can be a standard procedure for small colorectal polyps suspicious for high-grade dysplasia to avoid incomplete removal of occult invasive cancer by cold snare polypectomy. As UEMR showed satisfactory outcomes for intermediate-size lesions and recurrent lesions after endoscopic resection, UEMR can be a standard procedure for these lesions. Regarding large lesions and rectal neuroendocrine tumors, comparisons of UEMR with current standard methods for them were lacking, and further investigations are warranted. Adverse events appeared comparable or less frequent for UEMR compared with CEMR but still existed. Therefore, careful implementation of this new technique in clinical practice is important for its widespread use.

Keywords: adverse events; colonic neoplasms; colonic polyps; colonoscopic surgery; colonoscopy.

FIGURE 1

Flow chart of the study selection process. RCT, randomized controlled trial; CSP, cold snare polypectomy; Intra bleeding, intraprocedural bleeding; Post bleeding, postprocedural bleeding

FIGURE 2

A small sessile lesion in the transverse colon removed by underwater endoscopic mucosal resection (UEMR). (a) White‐light image of an 8‐mm sessile lesion in the transverse colon. The surface of the lesion appears slightly irregular. (b) Magnified narrow‐band image of the lesion in the dual‐focus mode. The microvessels appear irregular, indicating high‐grade dysplasia (JNET Type 2B). (c) Mucosal defect after UEMR. (d) Histopathological findings of the resected specimen, indicating minute invasion (200 μm)

FIGURE 3

An intermediate‐size sessile lesion in the sigmoid colon removed by underwater endoscopic mucosal resection (UEMR). (a) Narrow‐band image of a 20‐mm non‐granular‐type laterally‐spreading tumor in the sigmoid colon. (b) Snaring without submucosal injection underwater. (c) Mucosal defect after UEMR. (D) Resected specimen. Pathological findings indicated high‐grade adenoma

FIGURE 4

A large sessile lesion in the ascending colon removed by underwater endoscopic mucosal resection (UEMR). (a) White‐light image of a 30 mm granular‐type laterally‐spreading tumor in the ascending colon. (b) Snaring without submucosal injection underwater. (c) Mucosal defect after UEMR

FIGURE 5

A recurrent polyp after polypectomy in the sigmoid colon removed with piecemeal underwater endoscopic mucosal resection (UEMR). (a) A narrow‐band image of an 8 mm, recurrent polyp at the sigmoid colon, accompanied with scar after previous endoscopic polypectomy at the anal side of the lesion. (b) Snaring without submucosal injection underwater. (c) Mucosal defect after UEMR with a small remnant. (d) Mucosal defect after additional UEMR. (e) Endoscopic image of the scar after UEMR at surveillance colonoscopy 1 year later