Background and Aims: The quality of colonoscopy is critically influenced by bowel preparation. Polyethylene glycol (PEG) is considered the gold standard regimen for bowel preparation, however due to the necessity of large volume of patient's tolerance is impaired, especially in the elderly population. Lactulose has been adopted in a few centers as a novel alternative for colonoscopy preparation. This study aimed to investigate the efficacy-safety profile of a lactulose-based bowel preparation in comparison to PEG for colonoscopy.

Methods: Prospective non-blinded comparative study, developed in two tertiary centers from July 2021 to April 2023. Outpatients undergoing colonoscopy were randomly divided into 2 groups: Group 1 (111 patients): PEG and Group 2 (111 patients): Lactulose. The following clinical outcomes were assessed for each group: degree of bowel clearance using the Boston Score, colorectal polyp detection rate, adenoma detection rate, tolerability and side effects.

Inclusion Criteria:

• Patients age ≥ 18 years
• Colorectal cancer screening
• Lower gastrointestinal bleeding
• Iron deficiency anemia
• Chronic diarrhea

Exclusion Criteria:

• Patients with previous colorectal surgery
• Pregnant
• Emergency colonoscopies
• Use of any other scheme or substance for bowel preparation different from those studied
• Incomplete information
• Clinical conditions considered unsuitable for sedation or colonoscopy

Data were extracted from a prospectively generated database, including consecutive outpatients from July 2021 to April 2023 who underwent diagnostic colonoscopy