What is the procedure for performing a colonoscopy?

Colonoscopy Procedure: Step-by-Step Guide

Colonoscopy is performed by inserting a flexible endoscope through the rectum to examine the entire colon from the dentate line to the cecum, with proper bowel preparation being essential for accurate visualization and successful outcomes. 1

Pre-Procedure Preparation

1. Bowel Preparation:

   • Patient adopts a liquid diet 1-2 days before the procedure
   • Administration of oral lavage solutions or saline laxatives until the bowel is clean
   • Proper bowel preparation is critical for accuracy and cost-effectiveness 1

2. Patient Positioning and Sedation:

   • Position patient in left lateral position
   • Administer mild sedation (though not essential for patients who can tolerate the procedure with minimal discomfort) 1
   • Monitor vital signs throughout the procedure (watch for hypoxia <85% O2 saturation and hypotension <90/50 mmHg) 1

Procedure Execution

1. Rectal Examination and Insertion:

   • Perform digital rectal examination
   • Insert the colonoscope through the anus with gentle pressure
   • Insufflate air/CO2 to distend the bowel for better visualization (CO2 insufflation is preferred) 1

2. Advancement Technique:

   • Use combination of torque steering, tip deflection, and shaft advancement
   • Reduce loops by withdrawing and straightening the scope when resistance is encountered
   • Navigate through key anatomical landmarks: rectum → sigmoid colon → descending colon → splenic flexure → transverse colon → hepatic flexure → ascending colon → cecum

3. Cecal Intubation:

   • Confirm cecal intubation by identifying the appendiceal orifice and ileocecal valve
   • Documentation of cecal intubation is essential for quality assurance 1

4. Withdrawal and Inspection:

   • Perform careful mucosal inspection during slow withdrawal (recommended minimum withdrawal time: 6-10 minutes)
   • Examine behind folds and flexures by using tip deflection and position changes
   • Look for polyps, masses, inflammation, or other abnormalities

5. Biopsy and Therapeutic Interventions:

   • Obtain biopsies of suspicious lesions
   • For patients with unexplained diarrhea, obtain rectal biopsies (100% of cases) and ideally right and left-sided colonic biopsies 1
   • Perform polypectomy for identified polyps using appropriate techniques (snare, hot/cold biopsy forceps)

Post-Procedure Care

1. Recovery Monitoring:

   • Monitor vital signs until patient is fully recovered from sedation
   • Observe for signs of complications (bleeding, perforation, sedation-related events)

2. Documentation and Follow-up:

   • Document procedure details, findings, interventions, and any adverse events
   • Provide written and verbal instructions to the patient
   • Schedule appropriate follow-up based on findings

Potential Complications and Management

• Perforation: Risk is approximately 1 in 1,000 for diagnostic colonoscopy, higher with therapeutic procedures 1
• Bleeding: Most common after polypectomy; may require endoscopic intervention 1
• Cardiopulmonary events: Account for about half of all adverse events, usually related to sedation 1

Quality Metrics

• Cecal intubation rate should exceed 95% 2
• Adenoma detection rate should be >25% in men and >15% in women 2
• Patient comfort should be monitored with <10% experiencing moderate or severe discomfort 1

Important Pitfalls to Avoid

• Inadequate bowel preparation: Results in missed lesions and incomplete examinations
• Rapid withdrawal: Associated with lower adenoma detection rates
• Incomplete polypectomy: Can lead to interval cancers (27% of interval cancers develop in segments of previous polypectomy) 1
• Inexperienced endoscopists: Higher risk of complications, particularly perforation 3
• Failure to recognize flat or depressed lesions: Particularly important in the proximal colon 1

By following this structured approach to colonoscopy, clinicians can maximize diagnostic yield while minimizing the risk of complications, ultimately improving patient outcomes in terms of morbidity and mortality related to colorectal disease.