 Background: Colonoscopy is not a perfect test. It misses a substantial number of neoplastic lesions and has some risk of missing cancer. Nearly all work on detection during colonoscopy has focused on the withdrawal phase of the examination. Thus, colonoscopy is typically performed by rapidly passing the instrument through the loops and bends of the colon in order to reach the tip of the cecum, and then performing a slow withdrawal in which the tip of the instrument is systematically deflected, and the mucosa is careful cleaned and suctioned, to expose all of the colonic mucosa for viewing. 