Reply to Wang et al.

10.1055/a-2674-1910

We are grateful to Wang et al. [1] for their interest in our article on underwater injection endoscopic mucosal resection (UIEMR) for colorectal polyps. As noted, the retrospective nature of our study is a limitation; however, our research followed a common stepwise approach for new endoscopic techniques, reporting a retrospective series [2] after demonstrating its potential utility in several initial cases [3]. A prospective trial is planned to validate the outcomes.

A question was raised regarding whether endoscopic submucosal dissection (ESD) or hybrid ESD might be more appropriate for suspected T1 colorectal cancer (CRC). According to the Japan Gastroenterological Endoscopy Society guidelines – the country where ESD originated – ESD is recommended for lesions not suitable for en bloc snare EMR [4]. Although lesions >20 mm often prompt consideration of ESD, those ≤30 mm may still be amenable to underwater EMR (UEMR), depending on specific conditions. In order to improve deep margin control in T1 CRC, we developed UIEMR, combining the advantages of UEMR with submucosal injection. Although the R0 resection rate was lower than with ESD, all of the Rx or R1 resections were due to horizontal margin positivity, and all seven T1 CRCs achieved negative vertical margins in our study [2]. In T1 CRCs, the vertical margin is crucial for determining curative resection, whereas the horizontal margin is considered supplementary [5]. Therefore, UIEMR may be a time- and cost-efficient option in selected cases, although further evidence is needed.

Regarding concerns about muscularis propria damage, the fact that the vertical margin was preserved, even in lesions with deep submucosal invasion, highlights the advantage of UIEMR for deep resections. Importantly, submucosal injection is facilitated underwater because of the reduced bowel distension, which helps in avoiding injection beyond the muscularis propria. Furthermore, buoyancy facilitates mucosal lifting and selective snare capture. Therefore, the risk of muscularis propria damage is thought to be low.

We thank Dr. Wang and colleagues for their comments and look forward to sharing future data and potential collaboration.

Publication History

Article published online:
28 October 2025

• References

• 1 Wang J, Fan Z, Liu L. Is the underwater injection endoscopic mucosal resection technique suitable for T1 colorectal cancer?. Endoscopy 2025;
• 2 Hirai Y, Toyoshima N, Takamaru H. et al. Procedural outcomes of a novel underwater injection endoscopic mucosal resection technique for colorectal polyps ≥10 mm. Endoscopy 2025; 57: 494-499
• 3 Hirata S, Toyoshima N, Takamaru H. et al. Underwater endoscopic mucosal resection with submucosal injection. Endoscopy 2023; 55 (01) E70-E71
• 4 Tanaka S, Kashida H, Saito Y. et al. Japan Gastroenterological Endoscopy Society guidelines for colorectal endoscopic submucosal dissection/endoscopic mucosal resection. Dig Endosc 2020; 32: 219-239
• 5 Pimentel-Nunes P, Libânio D, Bastiaansen BAJ. et al. Endoscopic submucosal dissection for superficial gastrointestinal lesions: European Society of Gastrointestinal Endoscopy (ESGE) Guideline – Update 2022. Endoscopy 2022; 54: 591-622