Polyethylene glycol is the gold standard of bowel preparation for colonoscopy. The most important disadvantage is high volume of this preparation. Sulphate based solution (SBS), low volume PEG + ascorbic acid and solution of magnesium citric acid and sodium picosulfate could be suitable substitution of polyethylene glycol.

This study will be unicenter, randomized and single blind. It focuses on studying the effectiveness of four preparations for bowel cleansing before colonoscopy. Polyethylenglycol (PEG) will be compared as a gold standard of bowel cleansing with low volume preparations: Sulfate-based solution (SBS), low volume PEG + ascorbic acid and solution of magnesium citric-acid and sodium picosulfate. The effectiveness will be rated according to a quality of bowel preparation (Boston Bowel Preparation Scale) and detection of a colorectal neoplasia. The aim of this project is to compare the effectiveness of each four preparations.

Primary endpoint: To compare a quality of bowel preparation. Secondary endpoint: To compare a detection of colorectal neoplasia in those preparations.

Main hypothesis: PEG as a gold standard of bowel cleansing preparation is not worse than the other compared preparations.

Secondary hypothesis: PEG is not worse in detection of colorectal neoplasia than the other compared preparations.

Methods: There will be 400 patients included in the project with all indications for colonoscopy (age ≥ 18 years, no upper age limit) except the exclusion criteria. The patients will be offered to participate in the study at the Endoscopy unit when arranging the examination. In case of agreement they will sign informed consent and they will be educated about the correct process of bowel preparation. They also get all the instructions in printed version and questionnaire of preparation tolerability. The advantages for the patients in study will be earlier date of colonoscopy. On the day of colonoscopy, the patients will submit the questionnaire and undergo standard colonoscopy examination.

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).

Inclusion Criteria:

• Individuls ≥ 18 years old undergoing colonoscopy for all indications except exclusion criteria

Exclusion Criteria:

• Active idiopathic bowel disease
• Chronic renal insufficiency
• Serious internal comorbidity
• Planned therapeutic colonoscopy
• No informed consent signed (with the study and/or with the colonoscopy)