Meta-analysis Favors Low-Residue Diet Before Colonoscopy

Meta-analysis Favors Low-Residue Diet Before Colonoscopy

Douglas K. Rex, MD, FASGE, reviewing Zhang X, et al. Gastrointest Endosc 2020 May 3.

This meta-analysis comparing a low-residue diet to a clear liquid diet the day before colonoscopy identified 20 relevant randomized controlled trials that were published between 2005 and 2019 and involved 4323 patients. Bowel preparation quality, polyp detection, and adenoma detection were similar with low-residue and clear liquid diets, but nausea, vomiting, hunger, and headache were all significantly lower with a low-residue diet. Tolerance was rated similarly, but patients who consumed a low-residue diet found it easier to finish the diet and were more willing to repeat it.

Douglas K. Rex, MD, FASGE


It’s clear that a low-residue diet performs better than clear liquids for several outcomes when used the day before colonoscopy. Remaining questions include:

  • How is the low-residue diet best translated into clinical practice to ensure patients only ingest the specified foods?
  • How many low-residue meals should be allowed the day before colonoscopy, and will this vary depending on whether the colonoscopy is a morning or afternoon procedure?
  • Do these diets work in difficult-to-prep patients (eg, constipated patients, those on opioids)?

Note to readers: At the time we reviewed this paper, its publisher noted that it was not in final form and that subsequent changes might be made.


Zhang X, Wu Q, Wei M, et al. Low-residual diet versus clear liquid diet for bowel preparation before colonoscopy: meta-analysis and trial sequential analysis of randomized controlled trials. Gastrointest Endosc 2020 May 3. (Epub ahead of print) (

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