A Multicenter Randomized Controlled Trial Comparing Two Bowel Cleansing Regimens for Colonoscopy After Failed Bowel Preparation

Failed bowel preparation for colonoscopy occurs commonly, but the optimal regimen for the subsequent attempt is unknown. High-volume preparations often are used but are not well studied. The objective of this study was to compare the efficacy, tolerability, and safety of 2 regimens for use after failed bowel preparation.A multicenter, endoscopist-blinded randomized controlled trial was conducted in patients who previously failed bowel preparation despite adequate compliance. Patients were randomized to 1 of 2 split polyethylene glycol (PEG) regimens, preceded by 15 mg bisacodyl: PEG 2 L the evening before and 2 L the day of colonoscopy (PEG 2+2L+bisacodyl), or 4 L and 2 L (PEG 4+2L+bisacodyl). All patients followed a low-fiber diet on both the third and second day before the procedure, followed by a clear fluid diet the day before and the morning of the colonoscopy. The primary outcome was adequate bowel preparation, defined as a Boston Bowel Preparation Scale total score of 6 or higher, with all segment scores of 2 or higher. Secondary outcomes included adenoma detection rate, advanced adenoma detection rate, sessile serrated lesion detection, cecal intubation rate, tolerability, and adverse events.A total of 196 subjects were randomized at 4 academic centers in Canada (mean age, 60.7 y; SD, 11.4 y; 44.9% were women). There were no significant differences between the PEG 2+2L+bisacodyl and the PEG 4+2L+bisacodyl groups in achieving adequate bowel preparation (91.2% vs 87.6%; P = .44). There were no significant differences with regard to mean adenoma detection rate (37.4% vs 31.5%; P = .41), advanced adenoma detection rate (18.7% vs 11.2%; P = .16), sessile serrated lesion detection (8.8% vs 5.6%; P = .41), and cecal intubation rate (96.7% vs 92.1%; P = .19). The 2 regimens were similarly well tolerated, but PEG 2+2L+bisacodyl was associated with a higher willingness to repeat the bowel preparation (91.2% vs 66.2%; P < .001).Split-dose 4 L-PEG with 15 mg bisacodyl, along with dietary restrictions, has similar efficacy as a higher-volume preparation, and should be considered for patients who previously failed bowel preparation (ClinicalTrials.gov number, NCT02976805).