 Options for an incomplete colonoscopy include several endoscopic and non-endoscopic modalities. Non-endoscopic modalities include radiologic studies such as CTMRI colonography as well as a retrograde barium study. Relative disadvantages of these modalities is the inability to remove colonic polyps, perform biopsies, and in the case of barium studies, a lower sensitivity for pathology. Alternative endoscopic modalities have been described that may assist in successfully completing colonoscopy Of these alternative methods, balloon-overtube assisted colonoscopy is the most promising, but this method has not been studied in a randomized, controlled fashion. In this study, we aim to compare balloon-overtube assisted colonoscopy versus standard colonoscopy for patients with prior incomplete colonoscopy. 