Water Exchange Colonoscopy Raises Adenoma Detection Rate

Switching from air insufflation to water exchange during outpatient colonoscopy insertion raised the adenoma detection rate by 14 percentage points in a real-world cohort of 4322 procedures, with the largest gains concentrated in the right colon, according to a propensity score–matched study published in Therapeutic Advances in Gastroenterology.¹ Although it added roughly 7 minutes to the average procedure, the technique also improved bowel cleansing and detection of larger, higher-risk lesions.

The findings, drawn from outpatient colonoscopies performed between January 2019 and October 2024 at a high-volume Taiwanese hospital, Dalin Tzu Chi Hospital, offer some of the first evidence that water exchange’s benefits hold up outside the controlled conditions of a randomized trial—and against an unusually strong comparator.

What Did the Real-World Data Show?

Researchers matched 2161 water exchange procedures to 2161 air-insufflation procedures on age, sex, body mass index (BMI), sedation, bowel prep regimen, and other clinical factors known to influence detection. Just over half of each cohort were male patients (50.2%); mean (SD) ages were equivalent, at 59.3 (12.3) years in the water exchange cohort and 59.1 (13.6) years in the air-insufflation cohort; BMIs were identical (25.2 kg/m²); rates of bowel prep with polyethylene glycol were identical (51.4%); and fewer patients in the water exchange vs air-insufflation cohort were fully sedated during their colonoscopy (61.9% bs 63.4%).

Colorectal cancer is the second-leading cause of cancer death worldwide, and adenoma detection rate is the quality metric most consistently linked to a colonoscopist’s ability to reduce that risk. In the matched cohort, the adenoma detection rate reached 57.9% with water exchange compared with 44.0% with air insufflation, a difference translating to a number needed to treat of 8. Notably, the air-insufflation group’s baseline adenoma detection rate of 44.0% exceeded the 26.5% pooled rate reported in earlier large real-world population-based studies,² meaning water exchange’s advantage persisted even against a high-performing standard technique rather than a low bar.

The largest improvement occurred in the right colon, where the adenoma detection rate rose from 18.0% with air insufflation to 31.8% with water exchange.¹ The method also raised detection of adenomas 10 mm or larger (8.7% vs 6.7%; P = .014) and sessile serrated lesions (1.9% vs 1.0%; P = .011), suggesting its benefit extends beyond diminutive polyps to lesions of greater clinical concern.

Bowel preparation quality may contribute to water exchange’s success, the authors noted. Water exchange’s continuous water infusion and suction removal of debris during insertion lifted adequate-preparation rates from 88.4% to 97.4% (P < .001), with the sharpest improvement again in the right colon, from 90.4% to 97.2% (P < .001). In multivariable analysis, water exchange remained an independent predictor of a higher adenoma detection rate (adjusted OR, 1.551; 95% CI, 1.279-1.882; P < .001), even after accounting for withdrawal time, suggesting the mucosal-cleansing effect may have driven the added detections.

Efficiency took a hit when total procedure time rose from 15.6 to 22.6 minutes, driven mainly by longer insertion. In this study, water exchange was offered as a self-pay option (US$15) chosen by patients after counseling, and all procedures were performed by 3 endoscopists with more than 15 years of experience and a combined 1000-plus water exchange cases each.

This time cost carries operational weight. That 7-minute difference is a real scheduling and staffing consideration for high-volume endoscopy units, although the study authors suggested it may be offset by fewer missed lesions and a reduced need for earlier repeat surveillance.

Where Do These Data Fit in the Managed Care Space?

For health systems and payers evaluating colonoscopy quality strategies, the study findings suggest water exchange is a reasonable lever for improving detection, particularly for units still working toward the 35% adenoma detection rate benchmark—so increased by the American College of Gastroenterology and American Society for Gastrointestinal Endoscopy in 2024—or lagging in sessile serrated lesion detection.³ But the 3-endoscopist sample, the retrospective single-center design, and the lack of cost-effectiveness or interval-cancer data mean broader claims about value require confirmation in prospective, multicenter research.¹

“These results show that using water instead of air is a superior way to improve colonoscopy quality in real-world practice,” the authors wrote. “While the procedure takes a few extra minutes, it significantly increases the chances of finding and removing dangerous growths, ultimately providing a more thorough and life-saving exam.”

Whether the modest time investment translates into fewer post-colonoscopy cancers and lower downstream costs remains an open question for the field to answer.

References

1. Chao YJ, Hsieh YH, Tang, CP, et al. Real-world evidence of water exchange colonoscopy improving adenoma detection rates: a propensity score-matched analysis. Ther Adv Gastroenterol. 2026:19:17562848261473395. doi:10.1177/17562848261473395
2. Fernandes C, Estevinho M, Cruz MM, et al. Adenoma detection rate by colonoscopy in real-world population-based studies: a systematic review and meta-analysis. Endoscopy. 2025;57(1):49-61. doi:10.1055/a-2382-5795
3. Bonavitacola J. Updated colonoscopy guidelines have implications on doctors, patients alike. AJMC. September 12, 2024. Accessed July 30, 2026. https://www.ajmc.com/view/updated-colonoscopy-guidelines-have-implications-on-doctors-patients-alike