Unit of Digestive Endoscopy,San Paolo Hospital,Milan 20090,Italy;
Section of Gastroenterology,Department of Emergency and Organ Transplantation,University of Bari,Bari 70124,Italy;
Unit of Digestive Endoscopy,University of Messina,Hospital"G.Martino",Messina 98121,Italy;
Colonoscopy; Bowel preparation; Cleansing agents; Polyethylene glycol; Adequate cleansing; Constipation;