The aim of this study was to determine whether segmental re-examination of the each segment (right colon, mid-colon, and left colon) could increase the proximal adenoma detection rate (ADR) and to evaluate the time-effectiveness of this approach.

The investigators prospectively recruited patients (aged ≥45 and ≤75 years) who were scheduled to undergo colonoscopy at our center. Patients were excluded if they had advanced colonic cancer, prior resection of the proximal colon, inflammatory bowel disease, or polyposis syndrome, or were unable to provide informed consent. In addition, if the quality of bowel preparation was unsatisfactory (Boston Bowel Preparation Scale [BBPS] score <2 in any segment of the colon), or if the cecum could not be intubated during the colonoscopy, patients were excluded.

A randomization list was generated with the randomization algorithm of random sorting, using Excel program. Included patients were randomly assigned to one of the two groups: segmental re-examination group, in which the each segment (right colon, mid-colon, and left colon) was examined twice segmentally; or control group, in which the withdrawal time in the each segment was about 2 minutes.

Inclusion Criteria:

• Patients (aged ≥45 and ≤75 years) who were scheduled to un- dergo colonoscopy

Exclusion Criteria:

• Patients who had advanced colonic cancer, prior resection of the proximal colon, inflammatory bowel disease, or polyposis syndrome, or were unable to provide informed consent.
• If the quality of bowel preparation was unsatisfactory (Boston Bowel Preparation Scale [BBPS] score <2 in any segment of the colon), or if the cecum could not be intubated during the colonoscopy, patients were excluded.