Inclusion Criteria:  All adult patients, aged 40 or above, undergoing outpatient colonoscopy in the Queen Mary Hospital in Hong Kong will be recruited.  Exclusion Criteria:  Patients will be excluded if they have history of inflammatory bowel disease, colorectal cancer, previous bowel resection, Peutz-Jeghers syndrome, familial adenomatous polyposis or other polyposis syndromes, bleeding tendency or severe comorbid illnesses for which polypectomy is considered unsafe. Moreover, after randomization, if the cecum could not be intubated for various reasons or Boston Bowel Preparation Scale (BBPS) score is <2, these patients will be excluded