Comparing Right-Sided Colon Adenoma and Serrated Polyp Miss Rates With Water Exchange and CO 2 Insufflation: A Randomized Controlled Trial

Introduction: Postcolonoscopy colorectal cancers primarily occur in the right-sided colon because of missed adenomas and serrated polyps (SPs). Water exchange (WE) improves cleanliness and visibility of the right-sided colon. We hypothesized that WE could reduce the right-sided colon adenoma (rAMR) and SP miss rate (rSPMR) compared with standard colonoscopy.

Methods: We randomly assigned 386 colonoscopy patients to insertion with either WE or CO 2 insufflation. During the first withdrawal, polypectomies were performed up to the hepatic flexure. A second endoscopist, blinded to the insertion technique, re-examined the right-sided colon. The miss rate was determined by dividing the number of additional adenomas or SPs by the total number detected in both examinations. The primary outcome was the combined rAMR and rSPMR.

Results: WE significantly decreased the combined rAMR and rSPMR (22.2% vs 32.2%, P < 0.001) and rSPMR alone (22.5% vs 37.1%, P = 0.002) compared with CO 2 insufflation, but not rAMR (21.8% vs 29.8%, P = 0.079). In addition, WE significantly increased the detection of SP per colonoscopy (SP per colonoscopy) in the right-sided colon (0.95 ± 1.56 vs 0.50 ± 0.79, P < 0.001). Multivariate logistic regression analysis showed that ≥2 SPs in the right-sided colon were an independent predictor of rSPMR (odds ratio, 3.47; 95% confidence interval, 1.89─6.38), along with a higher right-sided colon Boston Bowel Preparation Scale score (odds ratio, 0.55; 95% confidence interval, 0.32─0.94).

Discussion: The significant reduction in rSPMR and increase in right-sided colon SP per colonoscopy suggest that colonoscopy insertion using WE is a valid alternative to CO 2 insufflation (clinical trial registration number: NCT04124393).