Split-dose low-volume polyethylene glycol is non-inferior but less preferred compared with same-day bowel preparation for afternoon colonoscopy.

Currently, the same-day polyethylene glycol-electrolyte lavage solution (PEG-ELS) regimen is particularly recommended for afternoon colonoscopy as an alternative to the split-dose regimen in western countries. However, in Japan, the split-dose regimen has never been used as a standard colonoscopy preparation regimen. The aim of this study was to compare the efficacy and tolerability of split-dose PEG containing ascorbic acid (ASC) with same-day single dose PEG-ASC in Japan.This was a single-blinded, non-inferiority, two-center, randomized, controlled study. In-hospital patients were randomized to the same-day regimen or the split regimen using a web-based registry system. The same-day group was instructed to take 5 mL of sodium picosulfate in the evening, and on the day of the colonoscopy, they took 1.5 L of PEG-ASC. The split group was instructed to take 1 L of PEG-ASC before the day of colonoscopy, followed by another 1 L of PEG-ASC on the day of colonoscopy. Bowel cleansing was evaluated by the Boston Bowel Preparation Scale.A total of 153 patients were randomized to either the same-day group (n=78, males 60.0%, mean age 62.7 years) or the split group (n=75, 61.3%, 61.9 years). The rates of successful bowel cleansing were 83.3% in the same-day group vs. 92.0% (83.4%-97.0%) in the split group, P=0.10). No serious adverse events occurred in the study population. However, more patients in the same-day group were willing to repeat the same preparation regimen (P<0.001). The split-dose regimen was not inferior to the same-day regimen with respect to the efficacy of bowel preparation, but the patients preferred the same-day regimen.