Efficacy and tolerability of a low-residue diet for bowel preparation: systematic review and meta-analysis

Background Colorectal cancer (CRC) contributes significantly to cancer mortality worldwide. In an effort to reduce the risk of death, detection of polyps through colonoscopy is crucial. The success of the colonoscopy depends on the diet administered the day before the test. Our aim was to evaluate the efficacy, tolerability, and adverse effects of bowel preparation when using a low-residual diet (LRD) compared to a clear-liquid diet (CLD) the day before a scheduled colonoscopy. Methods PubMed/Medline, Embase, the Cochrane Central Register of Controlled Trials (CENTRAL) and Scopus databases were searched. We included studies of patients undergoing a scheduled colonoscopy for CRC screening and surveillance or for diagnostic purposes that compared a LRD with a CLD the day before the colonoscopy. Efficacy, the primary outcome, was evaluated as the rate of adequate bowel preparation. Secondary outcomes were tolerability and adverse effects of bowel preparation. Results Thirteen RCTs ( N = 2587) were included. Patients receiving a LRD compared to a CLD showed no difference in adequate bowel preparations (RR 1.02; 95% CI 0.99–1.05; I 2 = 60%). However, the LRD improved patient tolerability (RR 1.17; 95% CI 1.12–1.23; I 2 = 66%) and had fewer adverse effects (RR 0.89; 95% CI 0.84–0.94; I 2 = 73%) compared to the CLD. Groups using a LRD with 4L of polyethylene glycol in a single dose or a LRD with < 2000 kcal < 32 g of fibres/day had better tolerability. Conclusion Based on these findings, our recommendation is strong in favour of a LRD for bowel preparation of patients undergoing a scheduled colonoscopy. This diet could also be useful as a preoperative colonic preparation, but this requires further research.