Water-Assisted Colonoscopy: Endoscopy| May 2026
Water-assisted colonoscopy (WAC), also known as hydrocolonoscopy, is an evolving insertion technique in which water is used instead of, or alongside, gas insufflation during colonoscope advancement. Over recent years, growing evidence has shown that WAC not only improves patient comfort but may also enhance adenoma detection and procedural quality.
Conventional air or CO₂ insufflation can elongate the colon, promote loop formation, increase angulations, and contribute to procedural discomfort. In addition, inadequate mucosal cleansing may impair adenoma detection.
The challenge is to achieve:
Less painful colonoscopy
Better loop control
Improved mucosal visualization
Higher adenoma detection rates (ADR)
without compromising procedural efficiency.
The principle behind WAC is maintaining the lumen minimally distended using water during insertion. Water exerts a gravitational effect that helps straighten the colon, reduces angulations, and minimizes loop formation. This translates into reduced patient discomfort and lower sedation requirements.
Two major forms are commonly used:
Water immersion
Water exchange
Among these, water exchange appears superior for reducing pain and improving ADR because residual stool and debris are aggressively washed away during insertion.
An additional benefit is improved mucosal visualization. Continuous irrigation cleans the mucosal surface, enhancing detection of subtle lesions and adenomas.
Water also has therapeutic advantages during endoscopic resection. During underwater polypectomy or EMR, water dissipates thermal energy and may reduce deep electrosurgical injury to the muscularis propria.
Many experienced endoscopists now use a hybrid dynamic approach, combining water and CO₂ selectively during insertion and withdrawal. Water helps traverse difficult angulations and clean the mucosa, while CO₂ is used strategically to expand folds during detailed inspection.
Overall, WAC represents a practical, low-cost technique that improves colonoscopy ergonomics, patient tolerance, mucosal visualization, and potentially adenoma detection without prolonging procedure time.
