Unrestricted vs three-day low-residue diet for colonoscopy preparation. Results of a feasibility randomized trial

To compare the impact of an unrestricted diet with a 3-day low-residue diet before colonoscopy on bowel preparation quality.

A randomized, multicenter, researcher-blinded, parallel-group feasibility trial was conducted to assess the efficacy of an unrestricted diet versus a 3-day low-residue diet for colonoscopy preparation. Participants, aged 50 to 69, were enrolled in a colorectal cancer screening program with no factors linked to poor bowel cleansing. The Boston Bowel Preparation Scale was used to evaluate colon preparation during intubation and withdrawal. Secondary outcomes included bowel exploration time, adenoma and polyp detection rates, and preparation and diet tolerability. The trial is registered under Clinical Trials (NCT04664543).

One hundred and two individuals (mean age 59.3 ± 5.5 years, 40.1% female) were randomly assigned to each diet. All participants in both groups achieved adequate preparation (Boston scores ≥ 2 in each segment). Complete adherence to preparation was observed in the majority of participants in both groups. No significant differences were noted between groups in withdrawal or cecal intubation times, or in adenoma detection rates. The unrestricted diet was better tolerated than the 3-day low-residue diet (82.5% vs. 32.3%). Preparation assessed during intubation was adequate in 82.5% of the unrestricted diet group and in 90.3% of the 3-day low-residue diet group.

It is feasible to test the impact of an unrestricted diet for adequate bowel preparation. Comparable cleansing results were achieved, but the unrestricted diet showed better tolerability.