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. 2025 Aug 12.
doi: 10.1007/s10620-025-09308-0. Online ahead of print.

Efficacy of Gel Immersion Tumor Characterization for Colorectal Lesions: A Pilot Study

Ken Inoue  1 , Naohisa Yoshida  2 , Reo Kobayashi  1 , Naoto Iwai  1 , Ryohei Hirose  1 , Osamu Dohi  1 , Hideyuki Konishi  1
Affiliations

Efficacy of Gel Immersion Tumor Characterization for Colorectal Lesions: A Pilot Study

Ken Inoue et al. Dig Dis Sci. .

Abstract

Background: Gel immersion endoscopy is a novel method that uses gel to enhance the visual field. This study aimed to analyze the efficacy of magnified endoscopy under gel immersion for optimal visualization and characterization of colorectal tumors.

Methods: We retrospectively examined 107 lesions observed with blue-laser/light imaging (BLI) or narrow-band imaging (NBI) between June 2022 and July 2023 using the Japan NBI Expert Team classification. The lesions underwent magnified endoscopy first with CO2 insufflation, then underwater, and finally under gel immersion. Visualization quality and diagnostic accuracy were evaluated. All colonoscopies were performed by three endoscopists (experienced: 2, less experienced: 1).

Results: Among the 107 lesions, the mean tumor size was 22.7 ± 11.8 mm and 58 lesions were non-polypoid. Histopathology revealed 15 sessile serrated lesions, one sessile serrated lesion with dysplasia, 36 low-grade dysplasias, 37 high-grade dysplasias, 14 adenocarcinoma (≥ T1) cancers, and four others. Gel immersion resulted in significantly less halation compared to CO2 insufflation (p < 0.0001), fewer bubbles than underwater (p < 0.0001), and less intestinal fluid compared to both CO2 insufflation and underwater (p < 0.0001). Visualization quality was significantly better with gel immersion than with CO2 insufflation and underwater (p < 0.0001). No significant differences were observed in the accuracy of the tumor characterization among the three methods.

Conclusions: The reduced halation, bubbles, and internal fluid with gel immersion provided excellent visualization. The diagnostic accuracy for colorectal lesions using the gel immersion method was comparable to that of CO₂ insufflation and underwater methods.

Keywords: Colorectal polyp; Gel immersion endoscopy; Magnified endoscopy.

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Conflict of interest statement

Declarations. Conflict of interest: Naohisa Yoshida and Osamu Dohi received a research grant from Fujifilm Co.. The system was rented from Fujifilm Co Ltd. The other authors have no conflicts of interest to declare. Ethical approval: This study was approved by the Clinical Ethics Committee on Human Experiments of Kyoto Prefectural University of Medicine (IRB registration number: ERB-C-1600; December 23, 2019). All procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and the Helsinki Declaration of 1964 and later versions. Informed consent for inclusion in the study or equivalent was obtained from all patients.

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