What is the Bristol regimen for bowel preparation?

Bristol Regimen for Bowel Preparation

The Bristol regimen for bowel preparation consists of 10 mg bisacodyl plus 2L polyethylene glycol electrolyte solution (PEG-ELS), which is particularly effective for patients with Bristol stool form types 1 and 2 (hard, constipated stools). 1

Patient Selection and Rationale

The Bristol regimen is specifically designed for patients with harder stool consistency as measured by the Bristol Stool Form Scale:

• Bristol Stool Form Scale types 1-2 indicate lower gastrointestinal motility and predict inadequate bowel preparation with standard regimens 2
• Patients with these stool types achieve significantly higher successful preparation rates with the Bristol regimen (88.7%) compared to standard 2L PEG-ELS alone (61.2%) 1
• The polyp detection rate is also significantly higher with the Bristol regimen (43.2% vs 25.7%) 1

Components of the Bristol Regimen

1. Medication components:

   • 10 mg bisacodyl tablet taken the evening before colonoscopy
   • 2L PEG-ELS solution

2. Dietary modifications:

   • Low-residue/low-fiber diet for breakfast and lunch the day before colonoscopy
   • Clear liquids only after starting the preparation 3

3. Timing of administration:

   • For morning colonoscopies: Split-dose with first half of PEG-ELS the evening before and second half beginning 4-6 hours before the procedure
   • For afternoon colonoscopies: Entire mixture can be taken on the morning of colonoscopy 3
   • Complete the preparation at least 2 hours before the procedure 4

Efficacy and Patient Tolerance

• The Bristol regimen achieves comparable bowel preparation quality to that seen in patients with normal stool consistency (Bristol types 3-7) 1
• Patients report higher acceptability with this regimen compared to standard preparation 1
• The addition of bisacodyl helps overcome the challenge of constipation without requiring excessive volumes of PEG solution

Special Considerations and Contraindications

• Avoid in patients with:

  • Renal insufficiency (creatinine clearance <60 mL/min/1.73m²)
  • Pre-existing electrolyte disturbances
  • Congestive heart failure
  • Cirrhosis or ascites 3

• Medication management:

  • GLP-1 receptor agonists should be stopped 1-7 days before the procedure 4, 3
  • ACE inhibitors/ARBs should be held on the day of preparation and procedure 3
  • Metformin should be reviewed in patients with borderline GFR 3

Monitoring and Follow-up

• Monitor for signs of dehydration during preparation
• Ensure adequate hydration before, during, and after preparation
• Bisacodyl has been associated with rare occurrences of ischemic colitis 3
• Baseline electrolytes and renal function should be assessed before the procedure 3

Alternative Approaches for Poor Preparation

For patients who have previously failed bowel preparation, an intensive regimen may be considered:

• Low-fiber diet for 72 hours
• Liquid diet for 24 hours
• Bisacodyl (10 mg) the evening before colonoscopy
• Split-dose PEG (1.5L evening before and 1.5L morning of colonoscopy) 5

This intensive approach has shown 90.2% adequate bowel cleansing in patients who previously had inadequate preparation 5.