Optimal intake of clear liquids during preparation for afternoon colonoscopy with low-volume polyethylene glycol plus ascorbic acid

BACKGROUND AND STUDY AIMS  The standard colonoscopy preparation regimen in Japan for afternoon procedures is sequential intake of 1 L of polyethylene glycol electrolyte lavage solution containing ascorbic acid (PEG-ASC), 0.5 L of clear liquid, 0.5 L of PEG-ASC, and finally 0.25 L of clear fluids (all at a rate of 0.25 L every 15 min). However, this regimen seems poorly tolerated and complicated for many patients compared to previous regimen of polyethylene glycol electrolyte lavage solution. The aim of this study was to evaluate an alternate regimen of 0.5 L of PEG-ASC followed by 0.25 L clear liquids, repeated 3 times. PATIENTS AND METHODS  This was a single-blinded, non-inferiority, randomized controlled study. Subjects were randomized to the standard regimen or the alternate regimen using a web-based registry system. All patients were instructed to eat a pre-packaged, low residue diet and to take sodium picosulfate hydrate the day before colonoscopy. The Boston Bowel Preparation Scale was used to evaluate bowel cleansing, and a 3-point scale was used to assess mucosal visibility. The primary endpoint was successful bowel cleansing. The acceptability, tolerability, safety, and endoscopic findings of these two regimens were secondary endpoints. RESULTS  A total of 409 patients were randomized to either the standard regimen (n = 204, males 54.0 %, mean age 65.5 years) or the alternate regimen (n = 205, 54.6 %, 65.0 years). The rates of successful bowel cleansing were 71.1 % (64.3 - 77.2 %) with the standard regimen vs. 75.1 % (68.6 - 80.9 %) with the alternate regimen (95 % lower confidence limit, for the difference = - 4.6, non-inferiority P  < 0.05). No significant differences were found in tolerability, safety, and endoscopic findings. CONCLUSION  The alternate regimen and standard regimen are clinically equivalent with respect to cleansing efficacy and acceptability, tolerability, safety, and endoscopic findings. These results are good news for patients with difficulty drinking the first liter of PEG-ASC.