Water Assisted-Colonoscopy (WAC or Hydrocolonoscopy)

Water immersion or assisted technique for colonoscopy (WAC) insertion has been noted to help reduce pain and occasionally makes difficult colonoscopies somewhat easier by straightening out the colon and reducing angulations (1, 2). WAC has been gathering interest in recent years due to high-quality studies offering evidence of the benefits of WAC to both the endoscopist and the patient (3-5). Water exchange may be superior to water immersion in minimizing colonoscopy discomfort and in increasing adenoma detection rates. The benefits of WAC arise from two principal mechanisms:

(I) Use of water exerts a gravitational effect and reduces colonic elongation, thereby reducing loop formation, procedure discomfort and sedation requirements (1-3).  

(II) Water irrigation improves mucosal views and can increase adenoma detection rates (ADR) (4).

The concept of keeping the lumen minimally distended with water appears to reduce angulations in the colon and facilitate advancement with less looping of the instrument. Compared with air insufflation, both water immersion and water exchange significantly reduce colonoscopy pain. Importantly, WAC does not compromise any other aspects of colonoscopy; for example, the procedure does not take longer with the water method (1-4).

In our practice we often perform “partial” WAC. This method consists of using water preferentially over CO2 during colonoscopy. Here we use the best of both worlds, water to traverse tight angulations, prevent elongation of the colon and clean the mucosal surface, and CO2 to open the lumen and flatten the folds when looking for colon polyps. With modern colonoscopes that allow for easy suctioning and generous use of water with the incorporated waterjet, the quality of the colonoscopy can be greatly improved using this hybrid, dynamic technique.

Furthermore, using lots of water during colonoscopy is essential to clean the mucosal surface and remove debris to improve detection of colorectal adenomas. Lastly, we want to emphasize that water is also is advantageous to perform some resections (“underwater endoscopic mucosal resection”) and is essential to clean the wound surface during and after polypectomy.

In sum, water is essential during colonoscopy, and can be used as the primary colon distention method (WAC) or as a hybrid dynamic tool to improve the results of colonoscopy.

Further reading:

1.     Friedland S. The water immersion technique for colonoscopy insertion. Gastroenterol Hepatol (N Y). 2010;6(9):555-6.

2.     Siau K, Beintaris I. My approach to water-assisted colonoscopy. Frontline Gastroenterology 2019;10:194-197.

3.     Leung CW, Kaltenbach T, Soetikno R, Wu KK, Leung FW, Friedland S. Water immersion versus standard colonoscopy insertion technique: randomized trial shows promise for minimal sedation. Endoscopy. 2010;42:557–563.

4.     Leung JW, Mann SK, Siao-Salera R, et al. A randomized, controlled comparison of warm water infusion in lieu of air insufflation versus air insufflation for aiding colonoscopy insertion in sedated patients undergoing colorectal cancer screening and surveillance. Gastrointest Endosc. 2009;70:505–510.

5.     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.

Hydrocolonoscopy on EndoCollab

  1. Hydrocolonoscopy - Key Concepts [Watch Now]

  2. Basic Endoscopy: The Concept of Hydrocolonoscopy [Watch Now]

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