The purpose of colonoscopy (colon examination with flexible tube and a camera) is to find early precancerous growth in the colon (polyps) and remove them before they turn into cancer. The doctor performing the procedure will first advance the colonoscope to the end of the colon (cecum) and then he will examine the colon for polyps while he is withdrawing the colonoscope. The period of time that the doctor spent examining the colon called "withdrawal time". Usually doctors will spend at least 6 minutes examining the colon after he reached the cecum. The investigators are proposing that dedicating half of the withdrawal time during colonoscopy in examining the right side of the colon, will increase the detection of polyps in the right side of the colon.

Research design: This is a prospective, randomized trial comparing the ADR between patients undergoing a screening colonoscopy in four different groups: 1) at least 3 minutes from the total withdrawal time dedicated to the right side of the colon, 2) at least 4 minutes from the total withdrawal time dedicated to the right side of the colon, 3) 6 minutes total withdrawal time regardless of time spent in any segment, 4) 8 minutes total withdrawal time regardless of the time spent in any segment. Randomization will be done in blocks after stratification. Four gastroenterologists and two fellows matched base on similar ADR and stratified on each arm of the study (segmental versus non-segmental withdrawal) will be performing the procedures. The estimated sample size of the four arms of the study is 400 patients.

Inclusion Criteria:

• adults undergoing colonoscopy for screening or surveillance purposes

Exclusion Criteria:

• prior history of colonic surgeries
• Crohn's colitis or ulcerative colitis
• prior history of colon cancer
• poor bowel preparation
• pregnancy