Comparative efficacy of combination of 1 L polyethylene glycol, castor oil and ascorbic acid versus 2 L polyethylene glycol plus castor oil versus 3 L polyethylene glycol for colon cleansing before colonoscopy: Study protocol of a randomized, double-blind, single-center study

Colonoscopy has been regarded as an important method of early diagnosing and treating gastrointestinal lesions; however adequate bowel preparation is critical one of many factors needed for successful colonoscopy. Although several modified or novel regimes have been developed, desired quality of bowel preparation has not yet been generated. Scattered evidences revealed that castor oil may have potential of effectively cleansing colon. It is noted that, however, prospective trial of exploring the value of castor oil in preparing bowel before colonoscopy is lacking. The aims of this study are to test the hypotheses that low dose castor oil (30 mL) may enhance potential of polyethylene glycol (PEG) and combination of low castor oil and ascorbic acid may halve the volume of PEG. This is a randomized, double-blind (endoscopist and assessor), single center trial with three-arm design. We will randomly assign 282 adult patients (≥18 years but < 75 years), who are scheduled to undergo colonoscopy, to receive either 3 L PEG alone, 2 L PEG plus 30 mL castor oil or combination of 1 L PEG, 30 mL castor oil and 5 g ascorbic acid. The bowel preparation quality based on Boston Bowel Preparation Scale (BBPS) is the primary outcome. The secondary outcomes include the first defecation time, total number of defecation, time of cecal intubation, detection rate of polyp and adenoma, willing to repeat the same regime, tolerance to regime, and adverse events. The study protocol has been approved by the Clinical Research Ethics Committees of Chongqing University Cancer Hospital & Chongqing Cancer Institute & Chongqing Cancer Hospital & Chongqing Cancer Center (2017[107]). The results from this trial will be submitted for publication in peer-reviewed journals, and will be presented at national and international conferences.