BACKGROUND AND AIMS Underwater EMR is an alternative way to have nonpedunculated colorectal lesions lifted before being resected. The endoscopist takes advantage of the behavior of mucosal lesions floating away from the muscular layer, once immersed in liquid. We performed a systematic review with meta-analysis to evaluate the efficacy and safety of this technique. METHODS Electronic databases (Medline, Scopus, EMBASE) were searched up to May 2018. Full articles including patients with colorectal lesions resected by the underwater EMR technique were eligible. The complete resection (primary outcome), en bloc resection, recurrence, and adverse event rates were pooled by means of a random or fixed-effect model. RESULTS Ten studies were eligible, providing data on 508 lesions removed from 433 patients (male/female = 239/194; mean age range 62.2-75.0 years). Six studies were performed in the United States and the other in Europe; 7 studies were prospective. The specific indications for performing underwater EMR varied widely across studies. The complete resection rate was 96.36% (95% confidence interval [CI], 91.77-98.44), with a rate of en bloc resection of 57.07% (95% CI, 43.20%-69.91%). The recurrence rate was 8.82% (95% CI, 5.78-13.25) in a mean endoscopy surveillance period of 7.7 months (range 4-15 months). The postprocedural bleeding rate was 2.85% (95% CI, 1.64-4.90). Bleeding during the procedure was always mild and was considered as part of the procedure in all series. The overall adverse event rate was 3.31% (95% CI, 1.97%-5.52%). No cases of perforation were reported. CONCLUSION According to the results of this systematic review, underwater EMR appears to be an effective and extremely safe technique for resecting nonpolypoid colorectal lesions.

中文翻译：

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水下EMR用于结直肠病变：荟萃分析（带视频）的系统评价。

背景与目的水下EMR是在切除未切除的未切除大肠的病变之前的另一种方法。一旦浸入液体中，内镜医师会利用粘膜病变从肌肉层浮走的行为。我们通过荟萃分析进行了系统评价，以评估该技术的有效性和安全性。方法检索截至2018年5月的电子数据库（Medline，Scopus，EMBASE）。包括通过水下EMR技术切除的结直肠病变患者在内的全文。完全切除（主要结局），整体切除，复发和不良事件发生率通过随机或固定效应模型合并。结果十项研究符合条件，提供了从433例患者中去除的508个病灶的数据（男性/女性= 239/194；平均年龄范围62.2-75）。0年）。在美国进行了六项研究，在欧洲进行了另一项研究。7项研究是前瞻性的。在整个研究中，进行水下EMR的具体指征差异很大。完全切除率为96.36％（95％置信区间[CI]，91.77-98.44），整块切除率为57.07％（95％CI，43.20％-69.91％）。在平均7.7个月（范围4-15个月）的内窥镜监测期间，复发率为8.82％（95％CI，5.78-13.25）。术后出血率为2.85％（95％CI，1.64-4.90）。手术过程中的出血总是轻微的，并且在所有系列中均被视为手术的一部分。总体不良事件发生率为3.31％（95％CI，1.97％-5.52％）。没有穿孔的报道。结论根据系统评价的结果，