Recommended Diet for Colonoscopy Preparation
For optimal bowel preparation before a colonoscopy, patients should follow a low-residue/low-fiber diet for early and midday meals on the day before the procedure, then switch to clear liquids for the evening meal. 1, 2
Dietary Recommendations
- Limit dietary modifications to the day before colonoscopy for patients at low risk for inadequate bowel preparation 2
- Follow a low-residue/low-fiber diet for early and midday meals on the day before colonoscopy 2, 1
- Avoid high-fiber foods such as cereals, beans, peas, nuts, seeds, and raw or dried fruits and vegetables on the day before colonoscopy 1
- Switch to clear liquids for the evening meal and continue until the procedure 1
- Additional days of dietary restrictions beyond one day before colonoscopy confer no benefit in bowel preparation adequacy 1
Evidence Supporting Low-Residue Diet vs. Clear Liquid Diet
- Low-residue diet has been shown to be non-inferior to clear liquid diet in terms of bowel preparation quality 3, 4
- Patients on low-residue diets demonstrate significantly higher odds of tolerability (OR 1.92) and willingness to repeat preparation (OR 1.86) compared to those on clear liquid diets 3
- Some studies even show superior bowel preparation with low-residue diet compared to clear liquid diet 5
- Patients on low-residue diets report less hunger and better fluid-intake perception 5
Bowel Preparation Regimen
- A split-dose administration of bowel preparation purgatives is strongly recommended for all patients, regardless of high-volume or low-volume preparation 2
- For split-dose regimens, the second portion should begin 4-6 hours before colonoscopy and be completed at least 2 hours before the procedure 2, 6
- Same-day regimen is an acceptable alternative to split dosing for afternoon colonoscopies 2, 6
- No specific bowel preparation purgative is superior to others for patients at low risk for inadequate preparation 2
- 2L bowel preparation regimens are suggested over 4L regimens when possible 2
Special Considerations
- For patients at high risk for inadequate bowel preparation (prior inadequate preparation, constipation, opioid use, diabetes, etc.), consider a more restrictive approach: clear liquids only on the day before colonoscopy 2
- For high-risk patients, a suggested regimen includes split-dose 4L polyethylene glycol-electrolyte lavage solution plus 15mg bisacodyl the afternoon before colonoscopy, with a low-residue diet 3 and 2 days before colonoscopy, changing to clear liquids the day before 2
- Discontinue iron supplements at least 7 days before colonoscopy to prevent dark, sticky stool that can obscure detection of polyps 1
Common Pitfalls to Avoid
- Unnecessarily restricting diet for more than one day before colonoscopy can reduce compliance without improving outcomes 1
- Failing to provide both verbal and written patient education instructions for colonoscopy preparation 2
- Not following split-dose regimen, which is superior to single-dose administration 2
- Consuming solid foods less than 6 hours before the procedure, which increases aspiration risk 6
- Failing to complete the bowel preparation at least 2 hours before the procedure 2
By following these evidence-based dietary recommendations, patients can achieve optimal bowel preparation for colonoscopy while maintaining better comfort and compliance with the preparation process.