Tip-in underwater endoscopic mucosal resection for a sessile lesion at a poorly visualized location

Endoscopic resection of proximal colonic lesions located behind the flexure is challenging because poor visualization of the oral side of the lesion makes it difficult to capture the entire lesion. Water immersion improves scope maneuverability and alleviates luminal angulation by reducing luminal distension [1]. Thus, underwater endoscopic mucosal resection (UEMR) could be effective for poorly visualized polyps such as orifice- or diverticular-related polyps [2] [3]. Nevertheless, suboptimal visualization of proximal margins in the deflated lumen would hamper assured snaring in UEMR [4]. We present a case of successful en bloc resection using tip-in UEMR of a proximal colonic lesion with poor visualization due to the location behind the flexure ([Fig. 1]).

Fig. 1 An endoscopic image of a 19-mm sessile lesion at the hepatic flexure.

A 68-year-old man was referred with a protruded lesion of 19 mm in size at the hepatic flexure. As the lesion was diagnosed as an adenoma, UEMR was attempted to improve scope maneuverability and its visualization. However, poor visualization of the oral side of the lesion did not ensure snare capturing of the entire lesion. To assure proximal margin, a spot-shaped mucosal incision at the proximal site of the lesion was made with a snare tip using a cut current ([Fig. 2]), and the lesion was within the snare ([Fig. 3]). Stable snare manipulation owing to an anchored tip could achieve en bloc resection without adverse events ([Fig. 4], [Video 1]). Histopathological examination revealed high-grade dysplasia ([Fig. 5]).

Fig. 2 The snare tip was anchored at the proximal mucosa using the cutting current to secure the resection margin and stabilize snare manipulation.

Fig. 3 The lesion was completely captured within the snare.

Fig. 4 An endoscopic image showing the post-tip-in UEMR defect without residue and perforation.

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Tip-in underwater endoscopic mucosal resection enabled en bloc resection of a hepatic flexure lesion with poor access by applying water immersion and snare anchoring to secure the resection margin.Video 1

Fig. 5 Histopathological examination showing high-grade dysplasia with negative margins.

In this case, tip-in UEMR has several advantages. First, reduced luminal distension could improve scope maneuverability and flexure angulation. Second, the tip-in maneuver could assure proximal margins even in poor visualization. Third, the anchoring snare tip could secure the snare capturing even where scope maneuverability was poor. This case suggests that tip-in UEMR is an effective technique for polyps with poor visualization and scope maneuverability.

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Contributorsʼ Statement

Keijiro Numa: Writing – original draft. Kenichiro Imai: Writing – review & editing. Kinichi Hotta: Supervision. Kazunori Takada: Writing – review & editing. Sayo Ito: Writing – review & editing. Hiroyuki Ono: Supervision.

Conflict of Interest

Author K. I. has received research grants from KANEKA Corporation, the Japanese Foundation for research and promotion of endoscopy, and the Japanese Gastroenterological Asociation, has received speaker honoraria from Olympus, Boston Scientific, and TOP Corporation, has consulting fees from Olympus and Boston Scientific, has receipts of equipment from Olympus and Boston Scientific, and has support for travel from Boston Scientific. The other authors declare no conflict of interest for this article.

• References

• 1 Leung FW, Leung JW, Mann SK. et al. The water method significantly enhances patient-centered outcomes in sedated and unsedated colonoscopy. Endoscopy 2011; 43: 816-821
• 2 Shiotsuki K, Imai K, Hotta K. Underwater endoscopic mucosal resection for complete R0 removal of an adenoma extending into the appendiceal orifice. Dig Endosc 2020; 32: e7-e8
• 3 Shiotsuki K, Imai K, Hotta K. et al. Underwater endoscopic mucosal resection for complete R0 removal of an adenoma extending deep into a colonic diverticulum. Endoscopy 2020; 52: E374-E375
• 4 Okumura T, Imai K, Hotta K. et al. Tip-in underwater endoscopic mucosal resection for a residual lower rectal lesion extending to the dentate line. Endoscopy 2023; 55 (Suppl. 01) E1252-E1253

Publication History

Article published online:
20 January 2026