Adenoma Miss Rate With Water Exchange vs Carbon Dioxide Colonoscopy

Inclusion Criteria: * Consecutive patients aged 20 years or older undergoing colonoscopy for screening and surveillance indications were considered for enrollment. Exclusion Criteria: * familial adenomatous polyposis and hereditary non-polyposis CRC syndrome, personal history of inflammatory bowel disease, previous colonic resection, inability to achieve cecal intubation, obstructive lesions of the colon, poor colon preparation, inability to completely remove a polyp, gastrointestinal bleeding, allergy to fentanyl or midazolam, American Society of Anesthesiology classification of physical status grade 3 or higher, mental retardation, pregnancy, and refusal to provide a written informed consent.