Prepackaged Low-Residue Diet "Clear-Through" Reduces the Required Volume of Polyethylene Glycol Solution for Colonoscopy Preparation: An Exploratory Randomized Controlled Study.

OBJECTIVES: Large volumes of polyethylene glycol (PEG) solution reduce patient acceptance of colonoscopy. A prepackaged low-residue diet (PLRD; Clear-Through) may improve bowel cleansing and allow further PEG reduction. This exploratory randomized study evaluated whether PLRD permits decreased PEG with ascorbic acid (PEG-Asc) volume while maintaining cleansing quality.

METHODS: In this single-center, endoscopist-blinded, three-arm randomized trial, 180 patients were allocated to Group A (self-adjusted diet + 1.5 L PEG-Asc), Group B (PLRD + 1.5 L PEG-Asc), or Group C (PLRD + 1.0 L PEG-Asc). The primary endpoint was cleansing quality using the Ottawa Bowel Preparation Score (OBPS). Secondary endpoints included bubble score, bowel movement frequency, adherence, tolerability, patient satisfaction compared with the previous colonoscopy, and adverse events. Logistic regression identified predictors of inadequate cleansing.

RESULTS: Baseline characteristics were comparable across groups. OBPS didn't differ significantly among the groups. Group C had significantly fewer bowel movements (p < 0.001) and a lower bubble score (p < 0.001). Adherence and tolerability were high, with no major adverse events. Reduced-volume preparation didn't negatively affect patient satisfaction; Group C had the highest proportion rating the preparation better than their previous experience (42.9%; p = 0.019). PLRD intake independently reduced the risk of inadequate right-colon cleansing (odds ratio 0.119; 95% confidence interval 0.043-0.327; p < 0.001).

CONCLUSIONS: PLRD allowed reduction of PEG-Asc to 1.0 L without impairing cleansing quality, while maintaining favorable patient satisfaction. PLRD may serve as a practical strategy to lessen patient burden during colonoscopy preparation.

TRIAL REGISTRATION: UMIN 000056459.