<qa>  What is the Boston Bowel Preparation Scale?- Bowel preparation will be evaluated using the Boston Bowel Preparation Scale. 9 Patients with 2 points in at least one of the three segments of the colon rectum plus left-side colon, transverse colon plus left and right flexure, right-side colon will be excluded from statistical analysis as well as those who after the beginning of the colonoscopy, had to be aborted because of an inability to reach the cecum by unfavorable anatomy or impassable tumors stenosis. 