Due to the increasing demand for colonoscopy in clinical practice, great interest has recently renewed for unsedated colonoscopy. Both Carbon dioxide Insufflation (CO2) and Warm Water Infusion (WWI) have been advocated to improve patient tolerance for colonoscopy as compared to standard Air Insufflation (AI). This study is aimed at evaluating the performance of the above techniques versus AI in unsedated patients.

Inclusion Criteria

• adult outpatients willing to undergo colonoscopy without routine initial sedation

Exclusion Criteria:

• refuse to initiate colonoscopy without routine sedation
• inadequate bowel preparation
• incapacity to give informed consent