Does Water Exchange Improve Adenoma Detection?

Summary and Comment |
March 31, 2017

Does Water Exchange Improve Adenoma Detection?

  1. Douglas K. Rex, MD

Randomized, controlled trial data suggest yes.

  1. Douglas K. Rex, MD

Water immersion (WI), or infusion of water during colonoscope insertion, is well known to reduce pain and to facilitate cecal intubation in patients with anatomically difficult colons. Unlike WI, water exchange (WE), involves simultaneous suctioning of dirty water during insertion, plus suctioning of residual air pockets.

In a multicenter, randomized, controlled trial, investigators compared adenoma detection rates (ADRs) among 1224 patients undergoing colonoscopy with air insufflation (AI), WI, or WE after split-dose bowel preparation. Insertion and withdrawal were performed by different colonoscopists (among 11 participating). The withdrawing endoscopist was blinded to the insertion method.

Cecal intubation time with WE was 9 minutes versus 8 in the other two arms, but total procedural time was similar in all three arms (about 21 minutes), as was withdrawal time. The Boston Bowel Prep Score (BBPS) was higher with WE (9 vs. 8 in the other two arms), resulting from higher BBPS in the ascending colon. Low percentages of patients and withdrawing doctors correctly guessed the insertion method, suggesting effective blinding.

ADR was significantly higher with WE (49%) versus AI (40%) but not WI (43%). The right colon ADR was also higher with WE versus AI (24% vs. 17%), as was the advanced right colon ADR (advanced adenomas plus sessile serrated polyps; 6% vs 3%). A center-specific analysis indicated that better preparation was critical to the improved ADR with WE.


These are the strongest data yet to support a role for WE in improving ADR, through the apparent mechanism of improved bowel preparation. Though increasingly convinced, I still have questions. How, after split dosing — which in our group's experience produces excellent right colon preparations — could additional improvements in BBPS produce more than a doubling of right colon advanced lesions? The main results for WE continue to come from the same core of investigators. Can these results be demonstrated by others?

Editor Disclosures at Time of Publication

  • Disclosures for Douglas K. Rex, MD at time of publication Consultant / Advisory board Covidien; Olympus Corporation America; Endo-Aid Ltd.; Endochoice; Boston Scientific; Paion AG; Ironwood Pharmaceuticals; Colonary Solutions; Novo Nordisk Inc.; Medscape Gastroenterology Grant / Research support: Braintree Laboratories Editorial boards World Journal of Gastroenterology; The Journal of Clinical Gastroenterology; Techniques in Gastrointestinal Endoscopy; Gastroenterology & Hepatology; Expert Review of Gastroenterology & Hepatology; Medscape Gastroenterology; World Journal of Gastrointestinal Pharmacology and Therapeutics; Annals of Gastroenterology & Hepatology; World Journal of Gastrointestinal Oncology; Comparative Effectiveness Research; Journal of Anesthesia & Clinical Research; Gastroenterology; World Journal of Gastrointestinal Pathophysiology; Gastroenterology Research and Practice; GI & Hepatology News; Gastroenterology Report; Clinical Epidemiology Reviews; JSM Gastroenterology and Hepatology (associate editor); GI Journal Watch; Austin Journal of Gastroenterology; World Journal of Gastrointestinal Pharmacology & Therapeutics Leadership positions in professional societies American Society for Gastrointestinal Endoscopy (Councilor); US Multi-Society Task Forces (AGA, ACG, ASGE) (Chair)


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