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HOME > Clin Endosc > Volume 58(6); 2025 > Article
Letter to the Editor A reformative underwater endoscopic mucosal resection technique for superficial non-ampullary duodenal tumors
Yiheng Yao1orcid, Guolei Shi2orcid, Xingjie Shen2,3orcid, Liang Liu2,3orcid
Clinical Endoscopy 2025;58(6):951-952.
DOI: https://doi.org/10.5946/ce.2025.115
Published online: June 27, 2025

1School of Clinical Medicine, Shandong Second Medical University, Weifang City, China

2Center of Digestive Endoscopy, Central Hospital Affiliated to Shandong First Medical University, Jinan, China

3Department of Gastroenterology, Central Hospital Affiliated to Shandong First Medical University, Jinan, China

Correspondence: Liang Liu Department of Gastroenterology, Central Hospital Affiliated to Shandong First Medical University, 105 Jiefang Road, Lixia District, Jinan, 250011, Shandong, China E-mail: lleveryground@163.com
• Received: April 10, 2025   • Revised: April 24, 2025   • Accepted: April 25, 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 reply "Reply to the comments on ‘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'" in Volume 58 on page 953.
We read with considerable interest the article by Nomoto et al.1 describing underwater endoscopic mucosal resection combined with saline injection to establish a novel anchoring technique (UEMR-A) for the treatment of superficial non-ampullary duodenal tumors (SNADETs), and are particularly intrigued by this innovative achievement. The findings of this study not only provide a safe and effective novel endoscopic approach for treating these tumors but also demonstrate that compared with conventional underwater endoscopic mucosal resection (UEMR-C), UEMR-A contributes to a significant improvement in the rate of R0 resection and shortens procedure times. However, although congratulating the research team on their accomplishment, we would like to raise certain issues regarding this technique for discussion.
It should be noted that in this study, the UEMR-A group comprised only 54 duodenal tumor cases, which represents a relatively smaller sample size compared with the 87 cases in the UEMR-C group. As highlighted by Schulz and Grimes,2 such sample size imbalances may compromise the statistical power of studies, particularly with respect to smaller groups, thereby reducing the sensitivity for detecting potential intergroup differences.
With regards to the single case of delayed bleeding reported in the study, previous research by Jaruvongvanich et al.3 has revealed that cardiovascular disease, hypertension, and other factors are significant risk factors for post-procedural delayed bleeding in colorectal resections. However, Nomoto et al.1 do not provide any detailed information regarding how patients were screened for underlying conditions during enrollment. These confounding variables may have influenced the study outcomes.
Moreover, whereas the authors base their conclusion that UEMR-A contributes to a higher rate of R0 resection on the findings of logistic regression analysis, they did not employ propensity score matching (PSM) to balance the groups. In addition, there were statistically significant differences in the proportion of expert and baseline differences, such as the lesion size and the location of the lesions between the two groups. These imbalances could potentially influence the validity of the conclusions reached. Employing PSM to adjust for these confounding variables would facilitate a more accurate evaluation of the actual differences between the two techniques, thereby enhancing the credibility of the results obtained.
Furthermore, Kiguchi et al.4 have reported an en bloc resection rate of 87% for UEMR-C, whereas Nomoto et al.1 obtained a rate of 93.1% using this technique. This discrepancy could well be attributable to heterogeneity in study design. As a retrospective single-center study, the findings may have been unduly influenced by specific institutional technical conditions and//or the operating endoscopists’ experience. We accordingly recommend that future research include multicenter randomized controlled trials to further validate the reproducibility and generalizability of the UEMR-A technique.
On the basis of evidence presented in the current literature and the findings of the study conducted by Nomoto et al.,1 it is recommended that future comparative studies on UEMR-A and UEMR-C for the treatment of SNADETs should prioritize multicenter randomized controlled trials and further increase the number of enrolled patients to minimize single-institution bias, whilst systematically collecting data on confounding factors such as patients’ underlying diseases. Furthermore, by controlling variables such as differences in operator experience, the therapeutic efficacy and safety advantages of UEMR-A could be more objectively validated.
  • 1. 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 Mar 12 [Epub]. https://doi.org/10.5946/ce.2024.181ArticlePubMed
  • 2. Schulz KF, Grimes DA. Sample size calculations in randomised trials: mandatory and mystical. Lancet 2005;365:1348–1353.ArticlePubMed
  • 3. Jaruvongvanich V, Prasitlumkum N, Assavapongpaiboon B, et al. Risk factors for delayed colonic post-polypectomy bleeding: a systematic review and meta-analysis. Int J Colorectal Dis 2017;32:1399–1406.ArticlePubMedPDF
  • 4. 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

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    • Reply to the comments on ‘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'
      Hironori Yamamoto, Yoshie Nomoto, Satoshi Shinozaki, Yoshimasa Miura, Hiroyuki Osawa
      Clinical Endoscopy.2025; 58(6): 953.     CrossRef

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      A reformative underwater endoscopic mucosal resection technique for superficial non-ampullary duodenal tumors
      Clin Endosc. 2025;58(6):951-952.   Published online June 27, 2025
      DOI: https://doi.org/10.5946/ce.2025.115
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