Research Article Split-Dose Polyethylene Glycol Is Superior to Single Dose for Colonoscopy Preparation: Results of a Randomized Controlled Trial Rachid Mohamed, 1 Robert J. Hilsden, 2,3 Catherine Dube, 4 and Alaa Rostom 4 1 Division of Gastroenterology, Faculty of Medicine, University of Calgary, Calgary, AB, Canada 2 Departments of Medicine and Community Health Sciences, University of Calgary, Calgary, AB, Canada 3 Forzani & MacPhail Colon Cancer Screening Centre, Alberta Health Services, Calgary, AB, Canada 4 Division of Gastroenterology, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada Correspondence should be addressed to Alaa Rostom; arostom@toh.on.ca Received 9 August 2015; Accepted 4 October 2015 Copyright © 2016 Rachid Mohamed et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Background. Te efcacy of colonoscopy in detecting abnormalities within the colon is highly dependent on the adequacy of the bowel preparation. Te objective of this study was to compare the efcacy, safety, and tolerability of PEG lavage and split-dose PEG lavage with specifc emphasis on the cleanliness of the right colon. Methods. Te study was a prospective, randomized, two-arm, controlled trial of 237 patients. Patients between the age of 50 and 75 years were referred to an outpatient university screening clinic for colonoscopy. Patients were allocated to receive either a single 4 L PEG lavage or a split-dose PEG lavage. Results. Overall, the bowel preparation was superior in the split-dose group compared with the single-dose group (mean Ottawa score 3.50 ± 2.89 versus 5.96 ± 3.53;  < 0.05) and resulted in less overall fuid in the colon. Tis efect was observed across all segments of the colon assessed. Conclusions. Te current study supports use of a split-dose PEG lavage over a single large volume lavage for superior bowel cleanliness, which may improve polyp detection. Tis trial is registered with ClinicalTrials.gov identifer NCT01610856. 1. Introduction Te efcacy of colonoscopy in detecting abnormalities within the colon is highly dependent on the adequacy of the bowel preparation. Despite advances in bowel preparation, the process remains difcult for patients to tolerate and complete and ultimately, if inadequate, can result in missed lesions [1]. With published literature on missed polyps and carcinomas at colonoscopy [2–4], optimal visualization of the colonic mucosa becomes critically important. Furthermore, some evidence suggests that colonoscopy may not be protective against right-sided colonic lesions [5, 6]. Subtle fat lesions with a predilection for the proximal colon, particularly those with serrated histology, are becoming increasingly signifcant as potential factors for the lack of protection of colonoscopy proximally and stress the importance of adequate prepara- tions [7–10]. Background. Polyethylene glycol (PEG) is a balanced elec- trolyte lavage rather than an osmotic agent; therefore its use as a bowel-cleansing preparation is typically associated with fewer fuid shifs and electrolyte abnormalities compared with low volume osmotic agents [11]. It has been widely used for colonoscopy preparation on its own [12–16] or in conjunction with other agents [17–20]. One disadvantage of the traditional 4 L PEG bowel preparation is a reduction in the quality of cleanliness with afernoon procedures [21], which has driven further research into timing and dosing of PEG depending on timing of the procedure [22–26]. In our previous study, the 4 L PEG preparation was somewhat inferior to sodium phosphate preparations (now removed from the market) because it lef a large amount of residual fuid in the colon [27]. However, the use of a split dose of PEG (2 L the day before the procedure and 2 L the morning of the procedure) may alleviate some of the shortcomings of a single 4 L preparation, particularly for afernoon procedures [28]. Te objective of this study was to compare the efcacy and tolerability of single- and split-dose PEG lavage, with specifc emphasis on the cleanliness of the right colon and the infuence of endoscopy time. Hindawi Publishing Corporation Canadian Journal of Gastroenterology and Hepatology Volume 2016, Article ID 3181459, 6 pages http://dx.doi.org/10.1155/2016/3181459