Attempted underwater en bloc resection for large (2-4 cm) colorectal laterally spreading tumors (with video).

Objective: To evaluate the feasibility and outcomes of attempted underwater en bloc resection (UEBR) of large colorectal laterally spreading tumors (LSTs).

Design: Prospective, observational study.

Setting: Tertiary academic referral center.

Patients: Fifty patients meeting the inclusion and exclusion criteria.

Interventions: Standardized UEBR technique involving attempted en bloc resection without submucosal injection by using a large 33-mm snare.

Main Outcome Measurements: Complete endoscopic en bloc resection, histologic complete resection, procedure time, adverse events, and follow-up data.

Results: Over 13 months, UEBR was attempted in 50 patients (median age, 68 years) with 53 LSTs 2 to 4 cm in size. The median LST size was 30 mm (range 20-40 mm). The median procedure and resection times were 38 minutes (range 17-87 minutes) and 3 minutes (range 1-32 minutes), respectively. Complete endoscopic en bloc resection with the 33-mm snare was successful in 29 of 53 lesions (55%). Of these, histology showed neoplasia-free margins in 79%. Final histology was tubular adenoma (n = 26), sessile serrated adenoma (n = 10), tubulovillous adenoma (n = 14), villous adenoma (n = 2), and intramucosal carcinoma (n = 1). Adverse events (4%) were delayed bleeding in 1 and abdominal pain in 1 patient each. There were no perforations. Forty patients with a total of 43 adenomas had follow-up colonoscopy with biopsies of the resection site after a median of 31 weeks (range 7-71 weeks) after resection. Residual adenoma was found in 2 of 43 (5%).

Limitations: Single-center, limited follow-up.

Conclusion: On an intention-to-treat basis, complete endoscopic en bloc resection was achieved in 55% of lesions with complete histologic resection verified in 79% of the en bloc specimens. UEBR without submucosal injection appears safe. Refinements are needed to improve UEBR success rates.