The Timing of Bowel Preparation Is More Important than the Timing of Colonoscopy in Determining the Quality of Bowel Cleansing

Abstract

We aimed to compare the quality of bowel preparation and cecal intubation rates between morning and afternoon colonoscopies and to evaluate the difference in quality of bowel preparation according to the intervals between starting and ending intake of bowel preparation agent and the initiation of colonoscopy. In this prospective study, 300 outpatients were instructed to drink PEG solution starting either at 5:00 a.m. (morning group) or at 8:00 a.m. (afternoon group) on the same day. The time when PEG intake was started and completed, and when colonoscopy was begun were recorded. The quality of bowel preparation was assessed using the Ottawa bowel preparation scale. There was no significant difference in the Ottawa scale between the morning and the afternoon groups (p = 0.14). Patients with intervals of 7 h or less between the initiation of PEG intake and the start of colonoscopy had a better quality of bowel preparation than those with intervals of more than 7 h (p = 0.03). In addition, patients with intervals of 4 h or less between the end of PEG intake and the start of colonoscopy had a better quality of bowel preparation than those with intervals of more than 4 h (p = 0.02). The time of day at which colonoscopy is performed, whether during the morning or the afternoon, does not have a significant impact on the quality of bowel preparation. The quality of bowel preparation is significantly better in patients with a shorter time between bowel preparation and the start of colonoscopy.