All subjects were instructed to take 4 bisacodyl tablets at 4:00 PM on the day before the procedure. Subjects allocated to the asymmetric split-dose regimen group were invited to consume at 6:00 PM on the evening before the colonoscopy 3 sachets of PEG-CS in 1,5 L of water in a range from 90 to 120 minutes (about 250 mL every 15 min) and 4 hours before the scheduled procedure 1 sachets in 0,5 L of water in a range from 15 to 30 minutes. Subjects allocated to the symmetric split-dose regimen group were invited to consume at 6:00 PM on the evening before the colonoscopy 2 sachets of PEG-CS in 1 L of water in a range from 60 to 90 minutes and 5 hours before the scheduled procedure 2 sachets in 1 L of water in a range from 60 to 90 minutes.