This was a randomized, single-blind, placebo-controlled study to evaluate the proportion of participants with abnormalities of the oral mucosa detected by visual examination of the oral cavity in the polyethylene glycol (PEG) 3350 group compared with the placebo group. The study was also to evaluate the proportion of participants with abnormalities of the esophageal mucosa detected by endoscopic examination of the esophagus in the PEG 3350 group compared with the placebo group, and to compare the safety and tolerability by evaluation of the proportion of participants with the occurrence of adverse events (AEs) or adverse drug reactions.