IntroductionInadequate bowel preparation is common and negatively impacts colonoscopy quality. The objective of this study is to compare two bowel preparation regimens in cleansing the colon after an index colonoscopy with failed bowel preparation.Methods and analysisThis is a phase III, multicentre, randomised clinical trial comparing two bowel preparation regimens after failure to adequately cleanse at the index colonoscopy. Regimen A consists of 4 L split-dose polyethylene glycol electrolyte solution (PEG-ELS) and Regimen B consists of 6 L split-dose PEG-ELS, both preceded by 15 mg of bisacodyl the day before the procedure along with a low-fibre diet 3 and 2 days before the procedure followed by a clear fluid diet starting the day before the procedure. The primary outcome is adequate bowel preparation, defined as a Boston Bowel Preparation Scale (BBPS) score of ≥6 with each segment score ≥2. Secondary outcomes include mean BBPS score, bowel preparation adequacy using the US Multi-Society Task Force on Colorectal Cancer definition, detection rate by polyp subtype, caecal intubation rate, mean Validated Patient Tolerability Questionnaire for Bowel Preparation score, subject willingness to repeat the preparation and faecal incontinence rate.Ethics and disseminationThe study will be conducted in accordance with Good Clinical Practice guidelines and local institutional standards. Study findings will be disseminated at an international gastroenterology conference and published in peer-reviewed journals.Trial registration numberNCT02976805; Pre-results.

INTRODUCTION: We investigated sleep disturbances, bowel movement (BM) kinetics, and travel experience with different bowel preparation regimens in a substudy of patients enrolled in a randomized multicenter Canadian clinical trial. METHODS:Patients scheduled to have a colonoscopy between 7:30 AM and 10:30 AM (early morning) were randomized to (i) 4-L single-dose polyethylene glycol (PEG) given in the evening before, (ii) 2-L splitdose PEG (1bisacodyl 15 mg), or (iii) 4-L split-dose PEG. Patients scheduled to undergo a colonoscopy between 10:30 AM and 4:30 PM (afternoon) were randomized to (iv) 2-L single-dose PEG (1bisacodyl 15 mg) in the morning, (v) 2-L split-dose PEG (1bisacodyl 15 mg), or (vi) 4-L split-dose PEG. Patients were asked to record information on BM kinetics, sleep, and travel to the endoscopy unit. Continuous and categorical variables were compared between groups using a Kruskal-Wallis test or x 2 test, respectively. Intention-to-treat analyses were performed. RESULTS:Overall, 641 patients were included in this substudy. Patients undergoing early morning colonoscopies reported the most awakenings in the night when assigned to 4-L single-dose day-before PEG and the highest reduction in sleep hours when assigned to 4-L split-dose PEG. There were no significant between-group differences in urgent BMs, fecal incontinence episodes, or travel interruptions. Overall, 17% of those traveling for more than an hour had to stop for a BM during travel, with no significant difference between groups.DISCUSSION:Day-before and split-dose high-volume PEG regimens for colonoscopies scheduled before 10:30 AM lead to the greatest sleep disturbance.