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HOME > Clin Endosc > Volume 58(4); 2025 > Article
Editorial Evaluation of a modified underwater endoscopic mucosal resection technique for duodenal neoplasms: clinical implications and future directions
Ji Yong Ahnorcid
Clinical Endoscopy 2025;58(4):544-545.
DOI: https://doi.org/10.5946/ce.2025.130
Published online: July 7, 2025

Department of Gastroenterology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea

Correspondence: Ji Yong Ahn Department of Gastroenterology, Asan Medical Center, University of Ulsan College of Medicine, 88 Olympic-ro 43-gil, Songpa-gu, Seoul 05505, Korea E-mail: ji110@hanmail.net
• Received: April 26, 2025   • Revised: May 13, 2025   • Accepted: May 14, 2025

© 2025 Korean Society of Gastrointestinal Endoscopy

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (https://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

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See the article "Utility of underwater endoscopic mucosal resection combined with a protruding anchor by saline injection for superficial non-ampullary duodenal tumors: a retrospective study in Japan" on page 561.
Superficial non-ampullary duodenal epithelial tumors (SNADETs) are among the most technically challenging and high-risk lesions for endoscopic resection because of the thin duodenal wall, narrow lumen, and complex duodenal anatomy.1 Although endoscopic submucosal dissection (ESD) can result in en bloc resection with clear margins, the perforation risk of ESD in the duodenum is higher than that in other parts of the gastrointestinal tract. Therefore, most endoscopists try safer modalities, such as conventional endoscopic mucosal resection (EMR), underwater EMR (UEMR), or argon plasma coagulation.2
Among these modalities, UEMR, which is a submucosal lift–free method that uses the buoyant effect of water, has been performed more frequently in SNADETs than other methods and shows safer and more complete resection.3 However, compared with ESD, UEMR does not have a high R0 resection rate, particularly in non-ampullary lesions compared to ESD and there is an increasing need for safer and more effective modalities for the endoscopic removal of SNADETs. In this context, a study by Nomoto et al.,4 published in this issue of Clinical Endoscopy, showed a novel technique called UEMR aided by a protruding anchor (UEMR-A), which is performed through targeted saline injection into the distal duodenal fold.
In a retrospective analysis of 141 patients with SNADETs, Nomoto et al.4 compared conventional UEMR (UEMR-C, n=87) with a novel, modified technique, UEMR-A (n=54), by injecting saline into the distal duodenal fold. The underlying principle of this technique is as follows: by making a mucosal protrusion just distal to the lesion with saline injection, the snare tip can be more precisely stabilized and anchored during resection, and the tumor can be easily removed for better control of the resection margins and improved visualization, even in anatomically challenging positions.
Despite the additional time required for saline injection, the median procedure time was significantly shorter in the UEMR-A group (4 vs. 6 minutes, p=0.018). More importantly, the R0 resection rate was substantially improved with UEMR-A compared with UEMR-C (83.3% vs. 60.9%, p=0.004), including a remarkable 100% R0 rate for anterior wall lesions and comparable outcomes, regardless of the endoscopists’ experiences.4 These findings suggest that UEMR-A may reduce the differences between endoscopists and technical dependence; therefore, less-experienced endoscopists can perform curative duodenal EMR more safely.
This study also demonstrated that the lateral resection margins were more frequently negative in the UEMR-A group than in the UEMR-C group (86.8% vs. 69.1%, p=0.02), proving that mechanical stabilization of the snare tip can lead to more consistent lateral margin control.4 During the procedure, there was no procedure-related perforation in either group, and delayed bleeding was found in one case in the UEMR-C group. Therefore, the new technique maintained a favorable safety profile with higher complete resection.
Several studies evaluated the efficacy of UEMR-C for superficial SNADETs. Kiguchi et al.5 reported an en bloc resection rate of 87% and an R0 resection rate of 67% for patients with UEMR-C, and Kato et al.6 observed an en bloc resection rate of 78.6% and an R0 resection rate of 56% in a large multicenter study involving 18 high-volume centers in Japan. These results show that although UEMR-C offers a safer alternative to ESD in the duodenum, this technique requires further improvement for higher curative resection. Other recent modifications to UEMR-C aimed to overcome the limitations of the resection rate. Takatori et al.7 showed that partial submucosal injection before UEMR could increase the en bloc resection rate to 96%, thereby enhancing visualization and control during snaring. However, this method involves broader mucosal lifting, which makes the procedure difficult in some cases, whereas UEMR-A introduces a more localized, controlled protrusion and creates an anchor point without extensive submucosal dissection. Therefore, Nomoto et al.4 suggested that the addition of a saline-induced protruding anchor, named UEMR-A, can significantly improve R0 resection rates, particularly for lesions located on the anterior or contralateral walls where snare is more difficult.
Despite the promising results of recent studies on the UEMR-A, some limitations should be considered. The study design was retrospective and single-center, with a chronological imbalance between the two groups because the UEMR-C method was performed earlier than the UEMR-A method. Because these two techniques were performed during different time periods, differences in the endoscopist technique and equipment availability may have contributed to procedural bias. Moreover, although the authors performed multivariate logistic regression, propensity score matching was not utilized to adjust for baseline imbalances, such as lesion location and endoscopist experience. These factors may have influenced the outcomes, and should be considered in future prospective trials.
In conclusion, UEMR-A can be considered an effective modality for the endoscopic resection of duodenal neoplasms. With further validation, this technique can be performed with a lower risk of complications and a higher rate of curable resection, even by inexperienced endoscopists. Building upon this technique, the development of more effective treatment techniques for duodenal tumors is expected in the future.
  • 1. Uozumi T, Abe S, Makiguchi ME, et al. Complications of endoscopic resection in the upper gastrointestinal tract. Clin Endosc 2023;56:409–422.ArticlePubMedPMCPDF
  • 2. Jeon HK, Kim GH. Endoscopic resection for superficial non-ampullary duodenal epithelial tumors. Gut Liver 2025;19:19–30.ArticlePubMedPMC
  • 3. Morais R, Amorim J, Medas R, et al. Underwater endoscopic mucosal resection vs conventional endoscopic mucosal resection for superficial nonampullary duodenal epithelial tumors in the Western setting. Clin Gastroenterol Hepatol 2025;23:79–88.ArticlePubMed
  • 4. Nomoto Y, Shinozaki S, Miura Y, et al. Utility of underwater endoscopic mucosal resection combined with a protruding anchor by saline injection for superficial non-ampullary duodenal tumors: a retrospective study in Japan. Clin Endosc 2025;58:561–568.ArticlePubMed
  • 5. Kiguchi Y, Kato M, Nakayama A, et al. Feasibility study comparing underwater endoscopic mucosal resection and conventional endoscopic mucosal resection for superficial non-ampullary duodenal epithelial tumor < 20 mm. Dig Endosc 2020;32:753–760.ArticlePubMedPDF
  • 6. Kato M, Takeuchi Y, Hoteya S, et al. Outcomes of endoscopic resection for superficial duodenal tumors: 10 years' experience in 18 Japanese high volume centers. Endoscopy 2022;54:663–670.ArticlePubMed
  • 7. Takatori Y, Kato M, Masunaga T, et al. Efficacy of partial injection underwater endoscopic mucosal resection for superficial duodenal epithelial tumor: propensity score-matched study (with video). Dig Endosc 2022;34:535–542.ArticlePubMedPDF

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        Evaluation of a modified underwater endoscopic mucosal resection technique for duodenal neoplasms: clinical implications and future directions
        Clin Endosc. 2025;58(4):544-545.   Published online July 7, 2025
        DOI: https://doi.org/10.5946/ce.2025.130
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