Underwater versus conventional endoscopic resection of nondiminutive nonpedunculated colorectal lesions: a prospective randomized controlled trial (with video)

Andrew W. Yen, Joseph W. Leung, Machelle D. Wilson, Felix W. Leung

Research output: Contribution to journalArticle


Background and Aims: Incomplete resection of colorectal neoplasia decreases the efficacy of colonoscopy. Conventional resection (CR) of polyps, performed in a gas-distended colon, is the current standard, but incomplete resection rates of approximately 2% to 30% for nondiminutive (>5 mm), nonpedunculated lesions are reported. Underwater resection (UR) is a novel technique. The aim of this study was to determine the incomplete resection rates of colorectal lesions removed by UR versus CR. Methods: In a randomized controlled trial, patients with small (6-9 mm) and large (≥10 mm) nonpedunculated lesions were assigned to CR (gas-distended lumen) or UR (water-filled, gas-excluded lumen). Small lesions in both arms were removed with a dedicated cold snare. For CR, large lesions were removed with a hot snare after submucosal injection. For UR, large lesions were removed with a hot snare without submucosal injection. Four-quadrant biopsy samples around the resection sites were used to evaluate for incomplete resection. Results: Four hundred sixty-two eligible polyps (248 UR vs 214 CR) from 255 patients were removed. Incomplete resection rates for UR and CR were low and did not differ (2% vs 1.9%, P =.91). UR was performed significantly faster for lesions ≥10 mm in size (10-19 mm, 2.9 minutes vs 5.6 minutes, P <.0001); ≥20 mm, 7.3 minutes vs 9.5 minutes, P =.015). Conclusions: Low incomplete resection rates are achievable with UR and CR. UR is effective and safe with the advantage of faster resection and potential cost savings for removal of larger (≥10 mm) lesions by avoiding submucosal injection. As an added approach, UR has potential to improve the cost-effectiveness of colonoscopy by increasing efficiency and reducing cost while maintaining quality. (Clinical trial registration number: NCT02889679.)

Original languageEnglish (US)
Pages (from-to)643-654.e2
JournalGastrointestinal Endoscopy
Issue number3
StatePublished - Mar 2020


ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging
  • Gastroenterology

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