Efficacy and tolerability of various bowel preparations in diabetic patients: a randomized controlled trial

Background and study aims  Diabetes mellitus (DM) is an independent risk factor for poor bowel preparation prior to colonoscopy. Bisacodyl is a stimulant laxative that may mitigate colonic dysmotility associated with diabetes. We hypothesized that adding bisacodyl to split-dose bowel preparation (SDBP) would improve the quality of bowel preparation among patients with diabetes. Patients and methods  Adult outpatients aged 18 to 80 years undergoing colonoscopy were recruited. One hundred and eighty-six patients with diabetes were randomly assigned to 1 of 3 treatment arms: 1) conventional 4 L of polyethylene glycol electrolyte lavage solution (PEG-ELS; conventional bowel preparation [CBP]); 2) split-dose of 4 L PEG-ELS (split-dose bowel preparation [SDBP]); or 3) split-dose of 4 L PEG-ELS preceded by 10 mg of oral bisacodyl 10 (SDBP-B). The primary outcome measure was bowel cleansing as indicated by Boston Bowel Preparation Scale (BBPS) score. Endoscopists were blinded to the preparation used. Secondary outcome measures were safety and patient tolerability. Results  Of the 212 patients randomized, only 186 received assigned bowel preparation. There were no differences among the three study groups with regard to age, indication, duration of DM, insulin use, narcotic use, or presence of end-organ diabetic complications. There was a trend toward better bowel preparation quality among those receiving SDBP and SDBP-B compared to those receiving CBP, but the trend was not statistically significant  ≥ 6 BBPS; 67 % vs. 83 % vs. 75 %, P  = 0.1). In terms of safety and tolerability, there were no differences among the three groups. Conclusion  Adding bisacodyl to SDBP does not improve the quality of bowel preparation in patients with DM. Further efforts are needed to optimize colonoscopy bowel preparation in this population.