It is a randomized controlled trial with tandem colonoscopy.Participants were randomized for use of either blue laser imaging or conventional White Light Colonoscopy on withdrawal method.comparison of detection and miss rates of BLI group Versus conventional White Light Colonoscopy.

blue laser imaging (BLI) are a new imaging systems used in endoscopy which are recently developed. According to three recently published reports, the diagnostic ability of adenoma characterization using blue laser imaging compares favorably with narrow band imaging. No published data are available to date regarding adenoma detection with blue laser imaging.BLI has the possibility to increase the detection of colorectal polyps by sufficient brightness and clearer endoscopic images.The investigators recruited participants who underwent colonoscopy for symptoms,screening,or surveillance.Participants were randomized for use of either blue laser imaging (BLI) or conventional white light colonoscopy on withdrawal method.Lesions detected on first-pass and second-pass examination were used for adenoma detection and miss rates,respectively.The primary outcomes is to compare the adenoma and poly detection rates of BLI with conventional white light Colonoscopy.

Inclusion Criteria:

• consecutive patients who were underwent colonoscopy in our center for diagnostic work up of colonic symptoms,surveillance of colorectal polyps, and colorectal cancer screening.

Exclusion Criteria:

• history of colon cancer, colectomy familial adenomatous polyposis, or inflammatory bowel diseases;
• severe intestinal stenosis or obstruction;coagulation，disorders;
• pregnancy;
• and colonoscopy examinations with inadequate bowel cleanliness