The quality of a bowel cleansing will be evaluated by the experienced endoscopists who will be blinded about a type of bowel preparation. The effectiveness will be assessed by the degree of bowel cleansing (Boston Bowel Preparation Scale) and ADR, aADR and number of cancers diagnosed. The GE unit staff will record all results in the on-line study database. Results will be statistically evaluated in Institute of Biostatistics and Analyses, Masaryk University, IBA MU).