Optimal withdrawal and examination in colonoscopy.

The primary goal of most colonoscopies, whether performed for screening, surveillance, or diagnostic examinations (those performed for symptoms or positive screening tests other than colonoscopy) is the detection of neoplasia and its subsequent removal by either endoscopic polypectomy or referral for surgical resection. Unfortunately, colonoscopy has proved to be a highly operator-dependent procedure with regard to detection. Variable detection results in some of the cancers that occur in the interval before the next colonoscopy.