S175 Water Exchange Increased Advanced Adenoma Detection in the Ascending and Proximal Colon As Compared to Air Insufflation

Abstract

Introduction: Randomized control trials (RCT) showed significant increase in adenoma detection rate (ADR) with water exchange (WE) compared with usual air or CO2 insufflation colonoscopy. Advanced adenoma detection rate (AADR) is a validated surrogate marker for colorectal cancer risk (GI Endosc Clin N Am 2002;12:1). There was limited data of the impact of WE on AADR, probably due to the small sample sizes of RCT. Pooled analysis of 6 published RCT suggested that WE significantly increased overall ADR and overall AADR of the entire colon (JCG 2020;54:212). The impact of WE on ADR and AADR in the ascending colon, where interval cancers tend to cluster (AJG 2014;109:1375), is unknown. We test the hypothesis that WE increased AADR by aggregating the data of 4 RCTs conducted by our group in Chiayi and Hualien, Taiwan. Methods: Data from 4 RCTs (NCT01894191, NCT02737514, NCT01535326, and NCT01699399) comparing WE and air insufflation were aggregated. The demographic characteristics, procedure related outcomes, ADR and AADR were tabulated. Results: Both the WE and air insufflation group included 503 patients. Table 1 shows that the demographic characteristics were similar between the two groups. WE had significantly shorter withdrawal time [mean (SD), 13.0 (6.8) vs 12.6 (8.5), P=0.017], and higher Boston Bowel Preparation Scale scores than the air insufflation group. The ratio of aspirate water volume to infused water volume at cecum (107%) indicated proper implementation of WE (Table 1). The WE group had significantly higher overall ADR (46.4% vs 54.9%, P=0.008), with the difference mainly occurring in the ascending colon (23.0% vs 30.9%, P=0.005) than the air insufflation group. The WE group had significantly higher AADR in the ascending (4.6% vs 7.8%, P=0.048) and proximal (6.4% vs 10.5%, P=0.023) colon. The overall AADR (16.3% vs 19.7%) was numerically higher in the WE group (P=0.189, possibly a type II error) (Table 1). Conclusion: Interval cancers tend to occur in the right and proximal colon. The beneficial effect for WE to increase right and proximal colon AADR (a validated surrogate marker for colorectal cancer risk) might hold the potential to reduce the occurrence of interval cancers. The aggregated data of 4 RCTs showed WE had significantly higher AADR in the right colon and proximal colon as compared to air insufflation. Future studies to evaluate the impact of WE on the occurrence of interval cancers are justified.Table 1.: †Chi-square test; ††Fisher’s exact test; *Mann-Whitney test; ADR, adenoma detection rate; AADR, advanced adenoma detection rate; BBPS, Boston Bowel Preparation Scale. Advanced adenoma was defined as an adenoma with a diameter of ≥ 10 mm, significant villous features (> 25%), or high-grade dysplasia. The ascending colon included the cecum, ascending colon and hepatic flexure. The proximal colon included the cecum, ascending and transverse colon.