Water-aided colonoscopy is rapidly becoming more widely adopted by lower gastrointestinal endoscopists, and has previously been shown to increase patient comfort, adenoma detection rate and bowel cleanliness, albeit potentially at the cost of increased insertion time [1]. Two main variations in technique exist. Water exchange (WE) involves only using water to distend the bowel and removing any gas already in the bowel; no gas insufflation at all is used on intubation with this technique. Water immersion (WI) uses water to facilitate insertion, but gas may be used. A hybrid technique describes the use of water to facilitate insertion through the left colon, up to the splenic flexure, with carbon dioxide used for insufflation proximal to the splenic flexure.
FG have just published the eagerly anticipated results of “Water infusion with exchAnge Versus ‘hybrid’ watEr infusion/CO2 insufflation for colonoscopy: a randomised study (WAVE)” [2]. This randomised trial seeks to systematically answer the question whether the true WE approach or a hybrid approach is better with respect to procedural efficiency, accuracy and tolerance.
Designed as a single-blind (participants, not endoscopists), prospective, randomised controlled trial, 246 patients were randomised to either a hybrid or WE intubation technique. After exclusions, 122 in each arm were included in the intention-to-treat analysis, and 111 hybrid and 115 WE in the per protocol analysis. Participant and procedure characteristics were well matched. The procedures were performed by one of four experienced endoscopists (prior experience of 1000-5000 colonoscopies) trained in both techniques.
The chosen primary outcome was total procedure time, used as a surrogate for procedural efficiency, with caecal intubation time, caecal intubation rate, various polyp detection metrics, loop formation, ancillary procedure performance, sedation use and comfort scores all as secondary outcomes.
So what did the authors find? Total procedure time and insertion time were both significantly longer in the WE group compared to the hybrid group (median 29 vs 25 minutes total procedure time, p = 0.009). In addition, more repositioning events were required in the WE group compared to the hybrid group, and 16% of endoscopists in the WE group had to abandon the technique due to factors such as looping and poor preparation; no technique changes were required in the hybrid group.
No differences in patient comfort nor polyp detection were seen between the two techniques, although the study was underpowered to detect any difference in the latter measure. More reverse alpha loops were identified in the hybrid technique, and the left colon bowel prep was significantly better in the WE group as might be expected.
Aside from the thoughtful and robust trial design, this trial had several strengths. It answers a highly relevant question for those of us who perform lower GI endoscopy and wish to optimise our procedures. Outcomes were clinically relevant, for both the patient and practitioner, and may have service implications in the case of reduced procedure time allowing for more efficient endoscopy lists. Future work should evaluate whether this hybrid technique improves lesion detection, and a health economic and environmental evaluation of various techniques could help inform recommendations going forward.
Overall this is a really exciting topic, and we would highly recommend reading this novel and well-written paper in the current issue of FG.
References
- Fuccio L , Frazzoni L , Hassan C , et al. Water exchange colonoscopy increases adenoma detection rate: a systematic review with network meta-analysis of randomized controlled studies. Gastrointest Endosc 2018;88:589-97.
- Ahmad A, Buenaventura A, Motes B, et al. Randomised trial of ‘hybrid’ water-assisted colonoscopy (modified water immersion) versus water exchange colonoscopy: WAVE study. Frontline Gastroenterology Published Online First: 29 April 2024. doi: 10.1136/flgastro-2023-102606
Author: Dr James Kennedy (Trainee Associate Editor)
Twitter: @DrJMKennedy
Declarations: I am a trainee associate editor for Frontline Gastroenterology