Bowel Preparation Guidelines for Colonoscopy
Split-dose bowel preparation is strongly recommended as the standard approach for all patients undergoing colonoscopy, with the second portion beginning 4-6 hours before the procedure and completing at least 2 hours prior to colonoscopy. 1
Dietary Recommendations
- Limit dietary modifications to the day before colonoscopy for patients at low risk for inadequate bowel preparation 1, 2
- Follow a low-residue/low-fiber diet for early and midday meals on the day before colonoscopy 1, 2
- Avoid high-fiber foods such as cereals, beans, peas, nuts, seeds, and raw or dried fruits and vegetables on the day before colonoscopy 2
- Switch to clear liquids for the evening meal on the day before colonoscopy 2
- Discontinue iron supplements at least 7 days before colonoscopy to prevent dark, sticky stool that can obscure detection of polyps 2
Bowel Preparation Regimens
Timing of Administration
- Split-dose regimen (preferred method): 1
- First dose: Evening before colonoscopy
- Second dose: Morning of colonoscopy, beginning 4-6 hours before the procedure and completing at least 2 hours prior
- Same-day regimen (alternative for afternoon procedures): 1
Volume Options
- Low-volume preparations (2L) are suggested over high-volume (4L) preparations for better patient tolerability while maintaining efficacy 1, 4
- Available preparation options include: 4, 5
- 2L PEG with ascorbic acid or citrates
- Oral sulfate solution (1L)
- Sodium picosulfate with magnesium citrate
Medication Considerations
- Avoid hyperosmotic regimens in patients at risk for volume overload or electrolyte disturbances 1
- For medications that may interact with bowel preparations: 6
- Do not take oral medications within 1 hour of starting each dose of bowel preparation
- For tetracycline, fluoroquinolone antibiotics, iron, digoxin, chlorpromazine, or penicillamine, take these at least 2 hours before and not less than 6 hours after bowel preparation
Special Considerations
For patients with previous inadequate preparation, modify the regimen with: 1
- Increased attention to communication of instructions
- Patient navigation support
- Restricting vegetables and legumes for 2-3 days before colonoscopy
- Clear liquids only on the day before colonoscopy
- Addition of promotility agents
- Treatment of underlying constipation
- Temporary cessation of constipating medications
Risk factors for inadequate preparation include: 2
- Cirrhosis
- Parkinson's disease
- Dementia
- Diabetes
- Constipation
Quality Assessment
- Bowel preparation quality should be assessed only after all washing and suctioning have been completed 1
- "Adequate bowel preparation" indicates that standard screening or surveillance intervals can be assigned based on colonoscopy findings 1
- Endoscopy units should track bowel preparation adequacy rates, with a target of 90% 1
Management of Inadequate Preparation
- When preparation is inadequate, reschedule colonoscopy: 1
- Within 12 months for screening or surveillance colonoscopies
- Within 3 months for abnormal non-colonoscopic colorectal cancer screening tests
- Same-day salvage options for inadequate preparations include: 1
- Large-volume enemas
- Through-the-scope enemas with completion colonoscopy on the same day
- Additional oral purgatives with same-day or next-day colonoscopy
Common Pitfalls to Avoid
- Unnecessarily restricting diet for more than one day before colonoscopy 2
- Completing preparation too early (>6 hours before procedure) decreases quality by approximately 10% for each additional hour 3
- Not considering patient-specific factors when selecting a preparation regimen 1
- Failing to provide both verbal and written instructions, which are essential for adequate preparation 1