Comparable quality of bowel preparation with single‐day versus three‐day low‐residue diet: Randomized controlled trial

Background and Aims There is controversy about the length of low‐residue diet (LRD) for colonoscopy preparation. The aim of the study was to compare one‐day vs. three‐day LRD associated to standard laxative treatment for achieving an adequate colonoscopy preparation in average risk subjects with positive fecal immunochemical test undergoing screening colonoscopy. Methods A non‐inferiority, randomized, controlled, parallel‐group clinical trial was performed in the setting of average risk colorectal cancer screening program. Participants were randomized to receive 1‐day vs. 3‐day LRD in addition to standard polyethilenglicol treatment. Adequacy of preparation was evaluated using the Boston Bowel Preparation Scale (BBPS). Primary outcome was achieving a BBPS ≥ 2 in all colon segments. Analysis was performed for a non‐inferiority margin of 5%, a 95% statistical power and one‐sided 0.05 significance level. Results A total of 855 patients were randomized. Adequate bowel preparation was similar between groups: 97.9% of patients in the 1‐day LRD group vs 96.9% in the 3‐day LRD group achieved the primary outcome (P‐value for non‐inferiority