Water-aided Colonoscopy vs Air Insufflation Colonoscopy in Colorectal Cancer Screening

The degree of protection afforded by colonoscopy against proximal colorectal cancer (CRC) appears to be related to the quality of the procedure, and the incomplete removal of lesions has been shown to increase the subsequent risk of developing a colon cancer.

Some studies suggest that small polyps with advanced histology are more common in the right than in the left colon (right colon proximal to splenic flexure, left colon distal to the splenic flexure). The average size of polyps in the right colon with advanced pathology or containing adenocarcinoma was ≤9 mm, whereas in the left colon their average size was \>9 mm, P\<0.001. Inadequate prevention of right-sided CRC incidence and mortality may be due to right-sided polyps with advanced histology or that harbor malignancy. These presumptive precursors of cancer are smaller and possibly more easily obscured by residual feces, and more likely to be missed at colonoscopy.

Water-aided colonoscopy (WAC) can be subdivided broadly into two major categories: water immersion (WI), characterized by suction removal of the infused water predominantly during the withdrawal phase of colonoscopy, and water exchange (WE), characterized by suction removal of infused water predominantly during the insertion phase of colonoscopy.

In some reports WE appeared to be superior to both WI and air insufflation colonoscopy (AI) in terms of pain reduction and adenoma detection, particularly for \<10 mm adenomas in the proximal colon.

In this multicenter, double-blinded randomized controlled trial (RCT) we test the hypothesis that that WE, compared to AI and WI, will enhance overall Adenoma Detection Rate (ADR) in CRC screening patients. Confirmation of the primary hypothesis will provide evidence that WE enhances the quality of screening colonoscopy.

We also hypothesize that WE may be more effective in detecting proximal colon adenomas than WI and AI, particularly \<10 mm adenomas, thus increasing proximal colon ADR and proximal colon ADR \<10 mm. Confirmation of secondary hypotheses will provide justification for further testing that WE may provide a strategy to improve prevention of colorectal cancer by increasing detection of adenomas in screening colonoscopy.

Unlike previous reports of single colonoscopist studies, the insertion and withdrawal phases of colonoscopy will be done by different investigators. The second investigator will be blinded to the method used to insert the instrument, thus eliminating possible bias about procedure related issues.

Several secondary outcomes will also be analysed.

Design: Prospective double-blinded multicenter randomized controlled trial. Methods: Colonoscopy with Air Insufflation, Water Immersion, Water Exchange to aid insertion of colonoscope; split dose bowel preparation. Sedation available at the start of the procedure or on-demand.

Control method: Air insufflation colonoscopy. Study methods: Water Immersion colonoscopy, Water Exchange colonoscopy.

Population: Consecutive 50 to 70 year-old screening patients. After informed consent, assignment to control or study arms based on computer generated randomization list with block allocation and stratification.

Primary outcome: overall Adenoma Detection Rate. Secondary outcomes: proximal colon ADR, Mean Adenomas resected per Procedure (MAP), cecal intubation rate and time, total procedure time (including biopsy and/or polypectomy), maximum pain during colonoscopy assessed during insertion and at discharge, the need for sedation/analgesia and its dosage. In addition loop reduction maneuvers, position changes, abdominal compression, the amount of infused and suctioned water during insertion and withdrawal, and patients willingness to repeat the examination will be evaluated.

Eligibility Criteria:
Inclusion Criteria:

* consecutive screening patients

Exclusion Criteria:

* previous colonoscopy within 5 years
* surveillance colonoscopy
* previous colorectal surgery
* indication for a proctosigmoidoscopy or bidirectional endoscopy
* history of inflammatory bowel disease
* patient refusal or inability to provide informed consent
* inadequate consumption of bowel preparation