Effective bowel cleansing is essential for a high-quality colonoscopy. However, strict pre-procedure dietary restrictions may burden patients and reduce compliance. This study assessed whether permitting a true low-fiber dinner on the day before colonoscopy affects bowel preparation quality or patient experience.

In this single center, prospective, investigator-blinded randomized controlled trial, 494 patients scheduled for colonoscopy received a split-dose polyethylene glycol (PEG) regimen (NER1006, Norgine) administered the evening (6 or 8 p.m.) and at least 6 hours before the procedure. Participants were randomized (1:1) to either a standard regime without proper dinner the day before (last low-fiber meal at 15h) or a more lenient regime allowing a low-fiber dinner, up to 2 hours before initiating bowel preparation. The primary outcome was adequate bowel cleansing, defined as a Boston Bowel Preparation Scale (BBPS) score ≥ 6 with no segmental score < 2, assessed by the endoscopists and an independent central reading. Secondary endpoints included other quality indicators, polyp (PDR), adenoma (ADR), advanced adenoma (aADR), and sessile serrated lesion (SDR) detection rates, and patient satisfaction.

Endoscopists’ BBPS scoring achieved an adequate bowel cleansing in 94.4% of the controls and 99.2% of the interventional group (p=0.061). Control and interventional groups demonstrated an optimal BPPS in 88.0% vs 84.9% (p=0.060), respectively. After central reading, adequate bowel cleansing was achieved in 99.1% of the controls and in 96.7% of patients with a more lenient dinner (p>0.999). Optimal cleansing was observed in only 68.7% vs 60.4%, respectively (p=0.0601).

Quality indicators PDR (73.5% vs 71.8%), ADR (49.4% vs 55.1%), aADR (17.7% vs 18.8%), and SDR (12.0% vs 11.0%) did not differ significantly between both groups. Patient satisfaction was not significantly different between groups, with 74.3% vs 73.1% reporting ≤1 negative feeling during bowel preparation (p=0.7604).

Permitting a low-fiber dinner up to 2 hours before starting bowel cleansing does not compromise the adequacy of colon cleansing with a split-dose PEG NER1006 regimen administered the evening and 6 hours before colonoscopy. Quality metrics and patient satisfaction remain high, indicating that a less restrictive dietary approach can be safely adopted. Central reading highlights the operator dependency of the BBPS scale prompting the need for objective tools like AI scoring systems.