Colorectal cancer remains the third most common cause of death from cancer worldwide. The adenoma detection rate is correlated with quality of colonoscopy and risk of postcolonoscopy CRC. Low quality of bowel preparation with fecal residue and brown liquid in the colon may lower the adenoma detection rate (ADR). Optimal bowel preparation and novel approaches for colonoscopy increases the effectiveness of colonoscopic examination to improve ADR are desirable. Water exchange, which significantly increased colon cleanliness both in the right colon and the entire colon, is characterized by insertion to the cecum in clear water in lieu of gas insufflations. Water exchange led to an increase in ADR, particularly for the improvement in the right colon, providing adequate bowel preparation.

NBI is an innovative imaging technology which efficiency for the early detection of superficial cancers in the head and neck region and the esophagus had been reported previously. In the colorectal region, different results have been reported for improvement in the adenoma detection rate of NBI compared with that of WLI. All procedures were performed up to the cecum by using a high-definition colonoscope (GIF-HQ290I; Olympus Optical ) However, whether NBI in high-definition colonoscope can increase the ADR after water exchange insertion, remains to be elucidated. The aim of this study was therefore to determine whether the use of NBI system as an adjunct to water exchange insertion would improve the ADR

Design: Prospective single-blinded randomized controlled trial. Patients were randomly assigned to control group or study group through a computer-based randomization list by a technician. See also inclusion and exclusion criteria.

Colonoscopy was performed using high-definition colonoscope (GIF-HQ290I) after bowel preparation. Experienced endoscopists (each with over 3000 colonoscopies performed) and fellows (performed more than 600 colonoscopies) performed all procedures. During the insertion phase, air pump was turned off to avoid inadvertent insufflations. Water exchange with infusion pump was used to open the lumen and simultaneous suction of infused water to allow passage of the scope in clear water. Suction of water can maximize cleanliness and minimize distension. Air pockets at any location of the lumen were always aspirated. In a collapsed colon, water turbulence formation at the tip of the scope facilitates residual feces removal, salvage cleansing also be provided during insertion. Simethicone was used to remove bubbles over the mucosa. Cecal intubation was defined as the passage of the scope tip beyond the ileocecal valve with visualization of the cecal appendix. After cecal intubation, as much residual water as possible was aspirated before beginning the withdrawal phase. The same endoscopist uses the same assigned method to perform tandem or back-to-back colonoscopy on all patients. After the first colonoscopic examination with the colonoscope removed from the anus, using the same entry method for insertion and the same assigned method for the second colon examination. In all arms, withdrawal lasted at least 9 minutes and was done using air insufflation to obtain adequate distension. A stopwatch was used to time the procedures, and time for polypectomy was not included.

Colon cleanliness was assessed using the Boston Bowel Preparation Scale (BBPS) and bubble scores. Cardiopulmonary function was monitored throughout, and adverse outcomes were recorded.

Study end points The primary outcome was to compare the ADR of the 290-NBI with the HD-WL. Secondary outcomes included Right and left colon Adenoma Detection Rate. Right and left colon <10 mm Adenoma Detection Rate. Mean adenomas resected per procedure. Cecal intubation rate. Cecal intubation time. Total withdrawal time. Amount of water used during the procedure. Adenoma and polyp miss rate between the two group.

Inclusion Criteria:

• • Any patient ≥40 and <85 who underwent colonoscopy, does not meet exclusion criteria mentioned below and provide written informed consent will be eligible for enrolment

Exclusion Criteria:

• • (1) history of inflammatory bowel disease;(2) familial adenomatous polyposis; (3) hereditary non-polyposis colorectal cancer syndrome; (4) personal history of colorectal cancer or had previous colonic resection; (5) haemodialysis; (6) an American Society of Anaesthesiologists class III or higher; (7) antiplatelet or anticoagulant therapy 5 days before the procedure

After the research has been finished