What are the evidence-based steps for a colonoscopy procedure?

Evidence-Based Colonoscopy Procedure Flowchart

Split-dose bowel preparation is the gold standard for colonoscopy preparation, with the second portion beginning 4-6 hours before the procedure and completed at least 2 hours prior. 1

Pre-Procedure Phase

Patient Education and Navigation

• Provide both verbal and written patient education instructions for all components of colonoscopy preparation 1
• Consider patient navigation including telephonic or virtual navigation using automated electronic messaging to improve preparation rates 1, 2
• Target a 90% adequate preparation rate at both endoscopist and unit level 1

Dietary Modifications

• Low-residue/low-fiber diet for breakfast and lunch the day before colonoscopy 1, 2
• Clear liquids only after starting the preparation 2
• Limit dietary modifications to the day before colonoscopy for low-risk patients 1
• For high-risk patients: consider restricting vegetables and legumes 2-3 days before procedure 1

Bowel Preparation Selection

• Consider patient's medical history, medications, and previous colonoscopy preparation results 1
• Avoid hyperosmotic regimens in patients at risk for volume overload or electrolyte disturbances 1
• Preferred regimen: 2L preparation instead of 4L regimen 1
• Consider oral simethicone as an adjunct 1

Timing of Bowel Preparation

• Split-dose administration (preferred method) 1, 2, 3:
  • First half: evening before colonoscopy
  • Second half: beginning 4-6 hours before colonoscopy, completed at least 2 hours before procedure
• Same-day regimen acceptable alternative for afternoon colonoscopies 1
• For morning colonoscopies, split-dose is superior to same-day regimen 1

Medication Management

• Hold ACE inhibitors/ARBs on day of preparation and procedure 2
• Review GLP-1 receptor agonists (stop 1-7 days before) 2
• Adjust metformin in patients with borderline GFR 2
• For medications like tetracycline, fluoroquinolones, iron, digoxin: take at least 2 hours before and not less than 6 hours after bowel preparation 3

Day of Procedure Assessment

Pre-Insertion Assessment

• When patients report incomplete adherence or dark bowel effluent, insert colonoscope to sigmoid colon to confirm inadequacy before aborting 1
• For inadequate preparation detected on arrival, consider:
  • Large-volume enemas 1
  • Additional oral preparation with same-day or next-day colonoscopy 1

Procedure Steps

1. Initial Assessment

• Position patient in left lateral position
• Perform digital rectal examination
• Insert lubricated colonoscope under direct visualization

2. Colonoscope Advancement

• Advance colonoscope with minimal air insufflation
• Use torque steering and loop reduction techniques
• Identify and navigate key anatomical landmarks (rectum, sigmoid, descending colon, splenic flexure, transverse colon, hepatic flexure, ascending colon, cecum)

3. Cecal Intubation

• Confirm cecal intubation by identifying ileocecal valve and appendiceal orifice
• Document cecal intubation with photographic evidence

4. Withdrawal and Inspection

• Perform careful mucosal inspection during withdrawal
• Maintain withdrawal time of at least 6 minutes for screening colonoscopies
• Use irrigation pumps to assist with clearing residual debris 1
• Complete washing and suctioning before assessing bowel preparation quality 1

5. Polyp Management

• Remove polyps as indicated using appropriate techniques (cold snare, hot snare, biopsy forceps)
• Retrieve and submit polyps for pathological examination

6. Preparation Quality Assessment

• Assess bowel preparation quality after all washing and suctioning 1
• Use standardized descriptors that communicate preparation adequacy 1
• Document whether preparation is adequate to assign standard screening/surveillance intervals 1

Post-Procedure Management

Follow-up Planning

• If preparation is adequate, assign standard screening or surveillance intervals based on findings 1
• If preparation is inadequate:
  • Reschedule within 12 months for screening/surveillance colonoscopies 1
  • Reschedule within 3 months for abnormal non-colonoscopic colorectal cancer screening tests 1

For Repeat Colonoscopy After Inadequate Preparation

• Modify bowel preparation instructions 1:
  • Increase communication of instructions
  • Increase patient navigation
  • Restrict vegetables/legumes 2-3 days before
  • Allow only clear liquids day before
  • Consider adding promotility agents
  • Treat underlying constipation
  • Temporarily stop constipating medications
  • Consider high-volume preparation regimens

Common Pitfalls and Caveats

• Avoid day-before regimens when possible as they result in inferior preparation quality 1, 4
• Do not prepare solutions in advance; reconstitute immediately before use 3
• Do not take other laxatives while taking prescribed bowel preparation 3
• Stop fluid consumption at least 2 hours before colonoscopy 3
• Avoid sodium phosphate preparations in patients with renal impairment 2, 3
• Monitor for signs of dehydration during preparation 2

By following this evidence-based flowchart, endoscopists can optimize colonoscopy preparation and procedure quality, leading to improved polyp detection rates and more accurate surveillance interval recommendations.