Conventional Endoscopic Mucosal Resection Research Articles

How to Manage the Large Nonpedunculated Colorectal Polyp

How to Manage the Large Nonpedunculated Colorectal Polyp

Curative value of underwater endoscopic mucosal resection for submucosally invasive colorectal cancer.

Occasionally, colorectal tumors without characteristics of deep submucosal invasion are found to be invasive upon pathological evaluation after endoscopic resection (ER). Because the resection depth for underwater endoscopic mucosal resection (UEMR) has not been clarified, we evaluated the feasibility of UEMR for pathologically invasive colorectal cancer (pT1-CRC). We retrospectively investigated data on the backgrounds and outcomes of patients with pT1-CRC who underwent UEMR between January 2014 and June 2019 at our institute. As a reference standard, the backgrounds and outcomes of pT1-CRCs that had undergone conventional EMR (CEMR) were also investigated. Thirty-one patients (median age, 68years [range, 32-88years]; 22 men [71%]) were treated with UEMR. Median lesion size was 17mm (range, 6-50mm). The endoscopic complete resection rate was 100%. The overall en bloc resection rate was 77%, and the VM0, HM0, and R0 resection rates were 81%, 58%, and 55%, respectively. In cases of pT1a (invasion <1000μm)-CRC (n=14), the en bloc, VM0, and R0 resection rates were 92%, 100%, and 71%, respectively. Seventeen patients (five with risk factors for lymph node metastasis and 12 without) were followed up, and no local recurrence and distant metastasis were observed during the follow-up period (median follow-up period, 18months [range, 6-62months]) after UEMR. The outcomes of UEMR seemed to be comparable with those of CEMR (n=32). The VM0 rate of UEMR for pT1-CRC, especially for pT1a-CRC, without characteristics of deep submucosal invasion seems feasible.

Utility of under-gel endoscopic mucosal resection with partial submucosal injection for a laterally spreading tumor.

Conventional endoscopic mucosal resection (EMR) is a widely used technique in the treatment of colorectal tumors. When resecting laterally spreading tumors (LSTs) with conventional EMR, the distal edge is difficult to dissect and tends to be piecemealed. However, the nongranular pseudodepressed type (LST-NG-PD) has a high risk of malignancy, requiring en bloc resection [1]. Endoscopic submucosal dissection (ESD) can ensure high en bloc resection rates, but it also has drawbacks such as high perforation rates, high cost, and long procedure times. Binmoeller et al. introduced underwater EMR (UEMR) as a useful alternative to ESD for LSTs [2]; however, treating the distal end remains a challenge and could cause segmental resection. In addition, the use of water in UEMR may impair clarity of view if bleeding occurs. Partial submucosal injection improves visualization of the distal edge [3], and gel immersion improves the endoscopic visual field [4] [5]. Here, we report that under-gel EMR with partial submucosal injection is an effective means of achieving en bloc resection of LST-NG-PD ([Video 1]).

Complete endoscopic removal of a large appendiceal orifice polyp.

A 51-year-old man was referred to our institution for removal of a large semipedunculated polyp (0-Isp) involving the appendiceal orifice ([Fig. 1]). Previous biopsies showed a tubulovillous adenoma (TVA) with high grade dysplasia (HGD). Endoscopic resection under general anesthesia in the operating room was proposed and was agreed to by the patient. A 30-mm 0-Isp lesion extending into the appendix (> 75 % of orifice) was found, with narrowband imaging showing a regular mucosal pattern without areas suggestive of deep invasion. Different endoscopic resection techniques were discussed at this point, such as endoscopic full-thickness resection (EFTR) and endoscopic submucosal dissection (ESD). However, the size, involvement of the appendiceal orifice, and presence of identifiable margins of the lesion favored conventional endoscopic mucosal resection (EMR) ([Video 1]).

A121 UNDERWATER EMR FOR NON-LIFTING SESSILE COLORECTAL LESIONS

Abstract Background Sessile colorectal lesions which do not elevate with submucosal injection — “non-lifting” lesions — are considered poor candidates for EMR due to concerns of possible invasive cancer and increased procedural risk. However, a non-lifting sign is an unreliable predictor of malignancy, relegating many benign lesions to surgical resection. Underwater EMR (UEMR), which obviates submucosal injection, is effective for sessile colorectal polyps but has not been evaluated specifically for non-lifting lesions. Aims The aim of this study was to assess the efficacy of UEMR for “non-lifting” large sessile colorectal lesions with the hypothesis that UEMR may have a clinical role in managing complex lesions. Methods We reviewed our database from 2016 to 2019 for patients referred for large (≥ 20 mm) non-lifting colorectal lesions without overt signs of invasive cancer, who subsequently underwent UEMR. Results Thirty-two cases were successfully treated with single session UEMR. 18 (56%) were de novo lesions whereas the remainder had undergone previous attempt(s) at conventional EMR. The mean lesion size was 37 ± 17 mm. 4 cases (13%) were resected en bloc; the remainder piecemeal. Final pathology was T1 adenocarcinoma, N=3 (9%); tubulovillous adenoma, N=15 (47%); tubular adenoma, N=8 (25%); sessile serrated, N=6 (19%); high-grade dysplasia, N=2 (6%). One patient with cancer underwent surgical resection (T1N0); the remainder had endoscopic follow-up over 8 ± 3 months with benign recurrent/residual lesions in 8%, all amenable to UEMR. There were no procedural complications. Conclusions In this series of large sessile non-lifting colorectal lesions, UEMR was effective for both de novo and previously treated lesions, obviating surgery in the majority of cases. Funding Agencies None

Efficacy of Underwater Endoscopic Mucosal Resection for Superficial Non-Ampullary Duodenal Epithelial Tumor.

Background/AimsEndoscopic resection (ER) for superficial non-ampullary duodenal epithelial tumors (SNADETs) is challenging. Conventional endoscopic mucosal resection (CEMR) is also problematic due to the anatomical features of the duodenum. We compared the safety and efficacy of underwater endoscopic mucosal resection (UEMR) with those of CEMR through a retrospective analysis. MethodsAltogether, 44 consecutive patients with 46 SNADETs underwent ER (18 CEMR cases and 28 UEMR cases) between January 2016 and October 2019. We investigated the proportions of en bloc resection, R0 resection, complications, resection time, and total procedure time and compared the outcomes of patients from the CEMR group with those of patients from the UEMR group. ResultsThe median tumor size was 8.0 mm (range, 2.0–20.0 mm). The UEMR group showed a higher proportion of en bloc resection (96.4% vs. 72.2%, p<0.05) and significantly lower median resection time and total procedure time (4 min vs. 9.5 min, p<0.05 and 13 min vs. 19 min, p<0.05; respectively) than the CEMR group. No complications were observed. However, two patients treated with piecemeal resection in the CEMR group had residual tumors. ConclusionsUEMR is a feasible therapeutic option for SNADETs. It can be recommended as a standard treatment.

Endoscopic submucosal dissection (ESD): how do Western endoscopists value animal models?

Introduction Endoscopic Submucosal Dissection (ESD)was introduced in the West later than in the East. Our aim was to assess how Western endoscopists performing ESD have been trained and how they value animal models for training. Material and methods An online survey regarding training in ESD was sent to Western endoscopists who published articles on advanced resection techniques. Results From 279 endoscopists, 58 (21%) completed the questionnaire, of which 50 confirmed performance of clinical ESD. Endoscopists had a median of 15 years of endoscopic experience (IQR 9.75–20.25) and all of them were performing conventional EMR, before starting ESD. Prior to clinical ESD, 74% (n = 37) underwent training with ex vivo models, 84% (n = 42) with live animal models and 92% (n = 46) with at least, one of the two models. After starting clinical ESD, as trainers, 52% (n = 26) were involved with ex vivo and 60% (n = 30) with live animal models. Personal usefulness of ex vivo and live animal models was rated with a median of 9 (IQR 8–10) and 10 (IQR 8–10), out of 10, respectively. Courses with ex vivo and live animal models were considered a prerequisite before clinical practice by 84% (n = 42) and 78% (n = 39), respectively. Conclusions Western endoscopists have extensive endoscopic experience before starting ESD. The majority had pre-clinical training with ex vivo and live animal models and more than half are acting as trainers of other endoscopists with these models. Animal models are considered very useful and deemed a prerequisite before clinical practice by the majority of the endoscopists.

Modified endoscopic mucosal resection techniques for treating precancerous colorectal lesions.

Endoscopic mucosal resection (EMR) is a technique allowing efficacious and minimally invasive resection of precancerous lesions across the entire gastrointestinal tract. However, conventional EMR, involving injection of fluid into the submucosal space, is imperfect, given the high rate of recurrence of post-endoscopic resection adenoma, especially after piecemeal resection. In light of these observations, modifications of the technique have been proposed to overcome the weakness of conventional EMR. Some of them were designed to maximize the chance of en bloc resection—cap-assisted EMR, underwater EMR, tip-in EMR, precutting, assisted by ligation device—while others were designed to minimize the complications (cold EMR). In this review, we present their modes of action and summarize the evidence regarding their efficacy and safety.

Underwater vs conventional endoscopic mucosal resection of large sessile or flat colorectal polyps：a prospective randomized controlled trial 1）.

Underwater vs conventional endoscopic mucosal resection of large sessile or flat colorectal polyps：a prospective randomized controlled trial^1）.

Appropriate endoscopic treatment selection and surveillance for superficial non-ampullary duodenal epithelial tumors

Objectives Superficial nonampullary duodenal epithelial tumors (SNADETs) have become frequently detected and referred for endoscopic resection (ER). However, optimal treatment methods and long-term outcomes after ER of SNADETs have not been fully elucidated. We aimed to clarify them by analyzing our large cohort of patients with SNADETs. Materials and methods We enrolled 190 consecutive tumors from 189 patients undergoing ER between January 2004 and September 2019. Cases were stratified into endoscopic submucosal dissection (ESD), conventional endoscopic mucosal resection, (CEMR) and underwater endoscopic mucosal resection (UEMR). Baseline characteristics and short-term outcomes were compared between the groups. Long-term outcomes were also investigated with a median follow-up of 36 months. Results ESD significantly exceeded CEMR (96.4% vs. 52.9%; p = .0026) and UEMR (96.4% vs. 50.0%; p = .0008) in complete resection rates for 11- to 20-mm lesions; the differences were not significant for lesions ≤10 mm. Local recurrence only occurred in patients with an incomplete resection. Only patients with submucosal invasion died from the primary neoplasms. The 3- and 5-year disease-free survivals were 91.3% and 83.5%. Conclusions While tumors ≤10 mm seem to be good indications for endoscopic mucosal resection, ESD should be considered for larger tumors to better achieve complete resection. Patients with submucosal invasive carcinomas have a great risk of cancer death. Therefore, a close follow-up and an additional treatment are desirable.

Outcomes of thermal ablation of the defect margin after duodenal endoscopic mucosal resection (with videos)

Laterally spreading lesions (LSLs) in the duodenum are conventionally treated by EMR. Recurrence is commonly encountered and can be difficult to treat safely due to the unique anatomic characteristics of the duodenum. Auxiliary techniques designed to prevent recurrence have not been described. We sought to evaluate the effectiveness of thermal ablation of the defect margin after EMR (EMR-T) in reducing recurrence at first surveillance endoscopy (SE1, scheduled at 6 months) in a single tertiary referral center. All duodenal LSLs≥10mm referred for EMR were eligible. After successful EMR, thermal ablation was performed using snare-tip soft coagulation around the entire circumference of the resection defect. The primary outcome was the frequency of recurrence at SE1. A previous, well-characterized, prospective cohort of duodenal LSLs≥10mm treated by conventional EMR was the comparator. Over 43 months up to October 2019, 54 LSLs underwent EMR-T. One hundred twenty-five LSLs underwent conventional EMR in the comparator group. Patient and lesion characteristics were similar between the groups. Recurrence was significantly lower in the EMR-T group compared with the conventional EMR group (1 of 49 [2.3%] vs 19 of 108 [17.6%]; P= .01). No difference in technical success, EMR-related adverse outcomes, or referral to surgery were identified between the groups. EMR-T significantly reduces the frequency of recurrence for duodenal LSLs. This technique is safe in the duodenum and has the potential to significantly improve the effectiveness of duodenal EMR. (Clinical trial registration number: NCT02306603.).

Underwater versus conventional endoscopic mucosal resection for colorectal lesions: a systematic review and meta-analysis.

Background and study aims Underwater endoscopic mucosal resection (UEMR) for colorectal polyps has been reported to have good outcomes in recent studies. We conducted a systematic review and meta-analysis comparing the effectiveness and safety of UEMR to conventional EMR (CEMR). Methods A comprehensive search of multiple databases (through May 2020) was performed to identify studies that reported outcome of UEMR and CEMR for colorectal lesions. Outcomes assessed included incomplete resection, rate of recurrence, en bloc resection, adverse events (AEs) for UEMR and CEMR. Results A total of 1,651 patients with 1,704 polyps were included from nine studies. There was a significantly lower rate of incomplete resection (odds ratio [OR]: 0.19 (95 % confidence interval (CI), 0.05–0.78, P = 0.02) and polyp recurrence (OR: 0.41, 95 % CI, 0.24–0.72, P = 0.002) after UEMR. Compared to CEMR, rates overall complications (relative risk [RR]: 0.66 (95 % CI, 0.48–0.90) ( P = 0.008), and intra-procedural bleeding (RR: 0.59, 95 % CI, 0.41–0.84, P = 0.004) were significantly lower with UEMR. The recurrence rate was also lower for large non-pedunculated polyps ≥ 10 mm (OR 0.24, 95 % CI, 0.10–0.57, P = 0.001) and ≥ 20 mm (OR 0.14, 95 % CI, 0.02–0.72, P = 0.01). The rates of en bloc resection, delayed bleeding, perforation and post-polypectomy syndrome were similar in both groups ( P > 0.05). Conclusions In this systematic review and meta-analysis, we found that UEMR is more effective and safer than CEMR with lower rates of recurrence and AEs. UEMR use should be encouraged over CEMR.

Outcomes of Gastrointestinal Polyps Resected Using Underwater Endoscopic Mucosal Resection (UEMR) Compared to Conventional Endoscopic Mucosal Resection (CEMR).

ObjectiveUnderwater endoscopic mucosal resection (UEMR) is reported to be superior to conventional endoscopic mucosal resection (CMER) for the complete resection of large polyps and may offer increased procedural efficiency.AimsTo compare recurrence rates and adverse events between UEMR and CEMR and define risk factors related to recurrence. Also, to assess recurrence rates in piecemeal endoscopic mucosal resection (EMR) based on the number of pieces resected.MethodsWe identified all patients with large polyps treated using the UEMR technique at Carilion Clinic, Roanoke, VA, USA between January 1, 2014 and December 31, 2017 with follow-up through October of 2018. We matched the UEMR patients with patients treated using the CEMR technique (1:2 matching, respectively). The Kaplan-Meier curve was used to estimate the cumulative risks of polyp recurrence. The Cox proportional hazard analysis was used to assess risk factors for developing polyp recurrence.ResultsSixty-eight patients (mean age: 63.4 ± 12.5 years; 52.9% males) with polyps removed using the UEMR technique (Group 1) were matched with 122 patients (mean age: 64.4 ± 10.0 years; 51.6% males) who had polyps removed using CEMR (Group 2). Polyps resected in fewer pieces (≤ 3) had lower recurrence rates compared to the ones resected in >3 pieces. Right colon polyps removed using UEMR had a lower recurrence rate compared to right colon polyps resected using CEMR. Polyp size and a high degree of dysplasia were associated with a high risk of polyp recurrence after resection. Completing advanced endoscopy training was also associated with a lower risk of recurrence.ConclusionUEMR had a lower recurrence rate compared with CEMR for right colon polyps. Factors associated with recurrence included the degree of training, high-grade dysplasia, and polyp size.

Piecemeal cold snare polypectomy versus conventional endoscopic mucosal resection for large sessile serrated lesions: a retrospective comparison across two successive periods

ObjectiveLarge (≥20 mm) sessile serrated lesions (L-SSL) are premalignant lesions that require endoscopic removal. Endoscopic mucosal resection (EMR) is the existing standard of care but carries some risk of adverse...

Effectiveness of underwater endoscopic mucosal resection versus conventional endoscopic mucosal resection for 10 to 20 mm colorectal polyps: A protocol of systematic review and meta-analysis.

Background:Endoscopic mucosal resection (EMR) is a standard method commonly for removing 10 to 20 mm colorectal polyps. While the incidence of residual or recurrent after conventional EMR is remarkably high. Underwater endoscopic mucosal resection (UEMR) as an alternative technique to conventional EMR for removing colorectal polyps has high adenoma detection and complete resection rates, improves patient comfort, decreases sedation needs, eliminates the risks associated with submucosal injection, and reduces snare and diathermy-induced mucosal injury. We will conduct a comprehensive systematic review and meta-analysis to compare the effectiveness of these two therapies in the management of 10 to 20 mm colorectal polyps.Methods:PubMed, Embase, Cochrane Library, Web of Science, China National Knowledge Infrastructure, China Science and Technology Journal Database and Chinese Biomedical Literature Database will be searched from inception of databases to November 2020 without language limitation. Two reviewers will independently conduct article selection, data collection, and assessment of risk of bias. Any disagreement will be resolved by discussion with the third reviewer. Review Manager Software 5.3 will be used for meta-analysis. The Cochrane risk of bias tool will be used to assess the risk of bias.Results:This study will provide a systematic synthesis of current published data to compare the effectiveness of UEMR and conventional EMR for 10 to 20 mm colorectal polyps.Conclusions:This systematic review and meta-analysis will provide clinical evidence as to whether UEMR is more effective and safer than conventional EMR for 10 to 20 mm colorectal polyps.Study registration number:INPLASY2020100006.

A Real-World Promising Result of Endoscopic Full-Thickness Resection: It's Time for Endoscopic Full-Thickness Resection to Be Widely Used.

During the past 2 decades, we have witnessed the rise and prevalence of endoscopic resection. Endoscopic full-thickness resection (EFTR) is a key technique in dealing with some difficult gastrointestinal lesions that are not eligible for conventional endoscopic mucosal resection or endoscopic submucosal dissection. However, EFTR is demanding with respect to endoscopic resection experience and defects closure skills, which limits its widespread use in clinical practice. Full-thickness resection device simplifies the operation and makes EFTR easier to master, even in low-level medical institutions. As the high-level evidence accumulates and technique improves, it's time for EFTR to be accepted and used by more and more endoscopists.

Underwater vs conventional endoscopic mucosal resection in treatment of colorectal polyps: A meta-analysis.

BACKGROUNDUnderwater endoscopic mucosal resection (UEMR) of colorectal lesions is emerging as an alternative method to conventional endoscopic mucosal resection (EMR); however, it is still controversial whether there is a difference in the effectiveness between UEMR and EMR.AIMTo evaluate the effectiveness and safety of UEMR in the treatment of colorectal polyps.METHODSClinical studies comparing the effectiveness or safety of UEMR in the treatment of colorectal polyps were searched in medical databases, including PubMed, Embase, Cochrane Library, CNKI, and Wanfang Data, monographs, theses, and papers presented at conferences. Statistical analyses were performed using Revman 5.3 software.RESULTSSeven non-randomized controlled trials and one randomized controlled trial met the inclusion criteria. In total, 1382 patients (1511 polyps) were included in the study, including 722 who received UEMR and 789 who received EMR. In the UEMR and EMR groups, the en bloc resection rates were 85.87% and 73.89%, respectively, with a relative risk (RR) value of 1.14 (95% confidence interval [CI]: 1.01-1.30; P < 0.05). In the sub-group analysis, the en bloc resection rate showed no statistically significant difference between the EMR and UEMR groups for polyps less than 20 mm in diameter. However, a statistically significant difference was found between the EMR and UEMR groups for polyps equal to or greater than 20 mm in diameter. The post-endoscopic resection recurrence rates at 3-6 mo of the UEMR and EMR groups were 3.26% and 15.17%, respectively, with an RR value of 0.27 (95%CI: 0.09-0.83; P < 0.05). The post-endoscopic resection recurrence rates of UEMR and EMR at 12 mo were 6.25% and 14.40%, respectively, with an RR value of 0.43 (95%CI: 0.20-0.92; P < 0.05). Additionally, the incidence of adverse events was 8.17% and 6.21%, respectively, with an RR value of 1.07 (95%CI: 0.50-2.30; P > 0.05).CONCLUSIONUEMR is an effective technique for colorectal polyps and appears to have some advantages over EMR, particularly with regard to some treatment outcomes.

Comparison of conventional and modified endoscopic mucosal resection methods for the treatment of rectal neuroendocrine tumors.

Small rectal neuroendocrine tumors (NETs) confined to the submucosa are endoscopically resectable. Because most rectal NETs are submucosal tumors, conventional endoscopic mucosal resection (cEMR) may not result in a complete resection. This study investigated whether modified EMRs, namely endoscopic submucosal resection with ligation (ESMR-L), EMR with precutting (EMR-P), and strip biopsy are superior to cEMR for achieving histologically complete resection (HCR) of rectal NETs. Medical records of 215 patients who were treated with endoscopic resections for rectal NETs between January 2011 and July 2019 were retrospectively enrolled. Of the patients, 110, 33, 29, and 43 underwent cEMR, ESMR-L, EMR-P, and strip biopsy, respectively. For each method, HCR and en bloc resection rates, procedure times, and complication rates were measured. HCR was achieved with cEMR, EMR-P, ESMR-L, and strip biopsies for 74.5%, 90.9%, 93.1%, and 90.7% of cases, respectively. The HCR rate for cEMR was inferior to those of the modified EMRs (p = 0.045 for cEMR vs. EMR-P; p = 0.031 for cEMR vs. ESMR-L; p = 0.027 for cEMR vs. strip biopsy). Among the three modified EMRs, there was no significant difference in achieving HCR (p = 1.000). En bloc resection (p = 0.096) and complication rates (p = 0.071) were not significantly different among the four EMR methods, although EMR-P required the longest procedure time (p = 0.000). All three modified EMRs are superior to cEMR and are equally effective for achieving HCR of rectal NETs.

S0139 Underwater vs Conventional Endoscopic Mucosal Resection for Colorectal Lesions: A Systematic Review and Meta-Analysis

INTRODUCTION: Underwater endoscopic mucosal resection (UEMR) for colorectal polyps has been reported to have good outcomes in recent studies. We conducted a systematic review and meta-analysis studying efficacy and safety of UEMR as compared to conventional EMR (CEMR). METHODS: A comprehensive search of multiple databases (through May 2020) was performed to identify studies that reported outcome of UEMR and CEMR for colorectal lesions. Odds ratio was calculated for outcomes comparing CEMR and UEMR. Outcomes assessed included adverse events, intra-procedural bleeding, delayed bleeding, perforation, post-polypectomy syndrome, incomplete resection, en bloc resection, R0 resection and rate of recurrence amongst UEMR and CEMR. Subgroup analysis was performed for non-pedunculated polyps ≥10 mm and ≥20 mm. All analysis was performed using RevMan 5.0 (Cochrane Collaboration). RESULTS: A total of 1,651 patients with 1,704 polyps were included from 9 studies. The mean age and polyp size ranged from 62.3 to 70 years and 9.9 mm to 30.2 mm, respectively. 66.4% of patients were males. Adverse events were 91 (10.2%) in CEMR group and 59 (7.2%) in UEMR group. Compared to CEMR, overall complications (odds ratio [OR]: 0.61 (95% CI, 0.42–0.88) (P = 0.009), and intra-procedural bleeding (OR: 0.54, 95% CI, 0.36–0.81, P = 0.003) was significantly lower with UEMR (Figure 1a and 1b). There was also a significantly lower rate of incomplete resection (OR: 0.19 (95% CI, 0.05–0.78, P = 0.02) and polyp recurrence (OR: 0.41, 95% CI, 0.24–0.72, P = 0.002) after UEMR (Figure 2a and 2b). Odds of R0 resection were significantly higher in UEMR as compared to CEMR with OR of 2.20 (95% CI, 1.26–3.83, I2 = 0, P = 0.0005) (Figure 2c). There were 1,204 polyps ≥10 mm (612 CEMR and 592 UEMR), and 294 polyps (166 CEMR and 128 UEMR) were ≥ 20 mm. The recurrence rate was lower for non-pedunculated polyps ≥10 mm (OR 0.24, 95% CI, 0.10–0.57, P = 0.001) and ≥20 mm (OR 0.14, 95% CI, 0.02–0.72, P = 0.01). The rate of en bloc resection, delayed bleeding, perforation and post-polypectomy syndrome were similar in both groups (P > 0.05). All results along with subgroup analysis are summarized in Table 1. CONCLUSION: In this systematic review and meta-analysis, we found that UEMR is safer and more effective than CEMR with lower rates of adverse events and recurrence. UEMR use should be encouraged over CEMR.Figure 1.: Forest plot showing odds ration of any complication (A) and intra-procedural bleeding (B) comparing conventional endoscopic mucosal resection and underwater endoscopic mucosal resection.Figure 2.: Forest plot showing odds ratio of incomplete resection (A), R0 resection (B) and recurrence (C) comparing conventional endoscopic mucosal resection and underwater endoscopic mucosal resection.Table 1.: All Results along with subgroup analysis of non-pedunculated polyps ≥ 10 mm and ≥20 mm comparing underwater and conventional endoscopic mucosal resection

S0967 Underwater vs Conventional Endoscopic Mucosal Resection for Colorectal Polyps: A Systematic Review and Meta-Analysis

INTRODUCTION: Underwater endoscopic mucosal resection (UEMR) has emerged as an attractive alternative to conventional EMR (CEMR) for the resection of colorectal polyps. The purpose of this systematic review and meta-analysis was to compare UEMR and CEMR for the resection of colorectal polyps with respect to efficacy and safety. METHODS: A comprehensive, systematic literature search was performed across multiple databases, including MEDLINE/PubMed, The Cochrane Library, CINAHL, Google Scholar, and Scopus from April to May 2020. Only studies that compared the resection of colorectal polyps using UEMR to CEMR were included. Outcomes examined included rates of en bloc resection, recurrence, post-procedure bleeding, perforation, and resection time. A meta-analysis was completed using the Mantel-Haenszel and DerSimonian and Laird models. RESULTS: Seven studies totaling 1237 polyps were included. 614 polyps were resected with UEMR, while 623 polyps were resected with CEMR. UMER was associated with over a two-fold increase in the rate of en bloc resection (odds ratio [OR], 2.08; 95% confidence interval [CI], 1.59–2.73, P < 0.001, I2 = 31%). UEMR was also associated with a significant reduction in the rate of recurrence (OR, 0.30; 95% CI, 0.16–0.57, P = 0.0002, I2 = 0%). There was no significant difference in post-procedure bleeding (OR, 1.11; 95% CI, 0.57–2.17, P = 0.76, I2 = 0%) or perforation (OR, 0.72; 95% CI, 0.19–2.83, P = 0.64, I2 = 0% CONCLUSION: The results of this systematic review and meta-analysis demonstrate that underwater EMR is a safe and efficacious alternative to conventional EMR technique. With appropriate training, underwater EMR may be strongly considered as a first line option in the resection of colorectal polyps.Figure 1.: Forrest plot of en bloc resection rates in UEMR vs. CEMR.Figure 2.: Forrest plot of recurrence rates following UEMR vs. CEMR at 3-6 month follow-up.Figure 3.: Forrest plot of post-procedure bleeding rates in UEMR vs. CEMR.