This trial will compare the efficacy of 2 different sets of dietary recommendations to be followed before colon cleansing for colorectal cancer screening colonoscopy.

There is no enough evidence in the literature to recommend a low-fiber diet for screening colonoscopy. Although evidence of benefit of a liquid diet is minimal and there is a growing body of evidence about the benefits of a liberalized diet, a high degree of heterogeneity in the clinical trials comparing the diet modifications before colonoscopy prevents a formal recommendation in current guidelines. A low-fiber diet the day before colonoscopy may result in same efficacy of bowel cleanliness, with an improved tolerability and acceptability.

All consecutive patients of a population-based colorectal screening cancer program referred for a colonoscopy will be invited to participate in the study. After obtaining informed consent, they will be randomized to one of the groups: liquid diet or low-fiber diet. The will be interviewed by a registered research nurse, and they will be provided with written instructions for bowel preparation and questionnaires for registering the data of the study. The day of the colonoscopy, questionnaires will be collected and endoscopists blinded for the study bowel preparation will perform the colonoscopy. Patients will be contacted for adverse events and a general satisfaction questionnaire, 3 days after colonoscopy.

Inclusion criteria:

• Consecutive patients referred for a colonoscopy in a population-based colorectal screening program.

Exclusion criteria:

• Unwillingness to participate.
• Inability to follow instructions
• Active inflammatory bowel disease
• Incomplete colonoscopies for technical reasons or contraindication as evaluated by the endoscopist