Bowel preparation is essential for achieving high-quality colonoscopy outcomes. Common preparatory protocols include the conventional single-dose polyethylene glycol (PEG) regimen and the increasingly utilized split-dose regimen. Our study aims to compare the quality of colonoscopies obtained using different protocols, based on the Boston Bowel Preparation Scale (BBPS).

This was a prospective, single-center study conducted in an endoscopy unit. All patients referred for diagnostic, screening, follow-up, or therapeutic colonoscopy were included.

All patients underwent bowel preparation along with a low-residue diet for one to three days. Participants were divided into two groups: Group 1( standard single-dose preparation of 4L the day before colonoscopy) and Group 2 (split-dose preparation, with 3 subgroups: A=3L the day before and 1L the morning of the examination, B= 2L the night before + 2L in the morning of the examination and C= 4L the day before and 2L the morning of the examination). Several parameters were studied: Tolerance of the preparation, adherence to the low-residue diet, BBPS, polyp detection rate (PDR), adenoma detection rate (ADR), mean number of polyps (MNP), and mean number of adenomas (MNA). Comparative statistical analysis of the different groups was performed using JAMOVI software.

248 patients were included in the study, with a median age of 57 years and a male-to-female ratio of 113/135. The indications for colonoscopies were: 77% diagnostic, 7.3% screening, 13.3% follow-up or surveillance, and 2.4% therapeutic.

Comparison of groups 1 and 2 with respect to bowel preparation quality and the detection rate of polyps and adenomas did not reveal any statistically significant difference. However, within group 2, subgroup b (2L the evening before + 2L the morning of) showed a significant superiority compared to the other subgroups and group 1, with a significant p-value of 0.011.

Multivariate analysis using binomial regression confirmed the absence of a significant influence of age, sex, or indication on bowel preparation quality.

The split-dose protocol, particularly subgroup b was better tolerated than the standard preparation, with a significant reduction in side effects (nausea, vomiting), and a p-value < 0.001.

The split-dose preparation proved more effective than the standard preparation in achieving good bowel preparation quality, as it was better tolerated. Among the different split-dose protocols, the subgroup 2b regimen offered the best compromise between efficacy and tolerability. Conversely, the 6L dose did not demonstrate superiority and proved more burdensome for patients.