During the preparation for colonoscopy each patient are observed for procedure tolerance. On the day of endoscopy, each patient evaluated the degree of the acceptance of the method of bowel cleaning (according to visual analog scale (VAS) and the occurrence of side effects (diary). The endoscopist performing colonoscopy, blinded for the bowel preparation regimen evaluate bowel cleansing and score it, according to the Aronchick and Ottawa scale. The rate of cecum intubation, and the colonoscopy complications (defined as bowel perforation and/or significant bleeding) are analyzed in each bowel preparation group.