A randomized single-blind trial of standard diet versus fiber-free diet with polyethylene glycol electrolyte solution for colonoscopy preparation

Background and study aims: Colonoscopy preparation usually involves the intake of large volumes of polyethylene glycol electrolyte solution (PEG-ES) in combination with a clear-liquid diet (CLD). Liberalization of the diet might enhance the tolerance to PEG-ES without compromising the quality of the preparation. The primary aims of this study were to evaluate the efficacy and tolerability of PEG-ES given with a CLD compared with a fiber-free diet (FFD) for colonoscopy preparation. The incidence of adverse events among patients in the two diet groups was also assessed as a secondary outcome. Methods: This was a single-center randomized, prospective, single-blind study. A total of 200 patients undergoing colonoscopy were randomized to either CLD or FFD in addition to PEG-ES. Results: Patients in the FFD group were able to drink more PEG-ES (mean +/- SD, 3.9 +/- 0.3 L) compared with those in the CLD group (3.3 +/- 0.7 L) (P < 0.01). The quality of the preparation was significantly better in the FFD group, with more patients having satisfactory preparations than those in the CLD group (81.4% vs. 52.0 %; P < 0.001). Tolerance to the preparation was higher in the FFD group compared with the CLD group, with significantly more patients adhering to the FFD regimen (P < 0.001). There were more adverse events experienced in the CLD group, with odds ratios of 1.9 for nausea (95% confidence interval [CI] 1.0-3.6), 3.8 for vomiting (95% CI 1.3-11.3), and 3.0 for headache (95% CI 1.5-5.9). Conclusion: FFD given with PEG-ES on the day before colonoscopy is a more effective regimen than the standard CLD regimen, and is better tolerated by patients.