How is anorectal retroflexion endoscopy performed in an adult patient, including positioning, bowel preparation, sedation, and equipment?

How to Perform Anorectal Retroflexion Endoscopy

Rectal retroflexion should be attempted in 90% of colonoscopy cases and involves bending the colonoscope tip backward 180 degrees in the rectum after initial forward examination to visualize the distal rectal mucosa and dentate line from below 1.

Technique and Procedure

Patient Positioning and Preparation

• Position patient in left lateral decubitus position (standard for colonoscopy)
• Ensure adequate bowel preparation (should be at least adequate quality in 90% of cases) 1
• Standard colonoscopy preparation protocols apply

Sedation Requirements

For patients undergoing colonoscopy with retroflexion:

• Age <70 years: Median dose of 50 mg pethidine (or 100 μg fentanyl) plus 5 mg midazolam 1
• Age ≥70 years: Median dose of 25 mg pethidine (or 50 μg fentanyl) plus 2 mg midazolam 1
• Conscious sedation is standard in most settings
• The procedure is well-tolerated and does not cause additional discomfort compared to standard forward viewing 2, 3

Equipment

• Standard colonoscope (140-degree or 170-degree angle of view)
• No specialized equipment required beyond standard colonoscopy setup
• Success rates of 94-100% have been reported with standard instruments 1

Step-by-Step Maneuver

1. Complete forward examination first: Carefully examine the rectum in forward view to the dentate line before attempting retroflexion

2. Positioning for retroflexion: After examining the rectum in forward view, position the scope tip in the mid-to-distal rectum

3. Execute the retroflexion:

   • Deflect the colonoscope tip maximally upward (toward the ceiling when patient is in left lateral position)
   • Simultaneously withdraw the scope slightly
   • The tip will bend backward 180 degrees, allowing visualization of the rectal vault from below

4. Systematic inspection: Examine the entire circumference of the distal rectum, focusing on:

   • The dentate line
   • Lower rectal mucosa
   • Areas that may have been tangential or hidden on forward view

5. Return to forward view: Straighten the scope and complete the examination

Success Rate and Contraindications

• Retroflexion is successful in approximately 94% of patients 2
• Do not attempt if:
  • Rectum appears narrow or contracted
  • Severe proctitis is present
  • Patient experiences significant discomfort during the attempt 4
• Unsuccessful or not performed in approximately 6% of cases due to anatomic constraints 2

Clinical Utility and Diagnostic Yield

Detection Benefits

The evidence shows variable but meaningful diagnostic yield:

• Increases adenoma detection by approximately 1% in screening populations 3
• Detects additional lesions in 2-8% of cases 1
• More than 50% of lesions in the rectal vault may be identified only by retroflexion 5
• Particularly useful for detecting small polyps (<5 mm) and lesions near the dentate line 5, 3

Important Caveat

The largest study (1,502 patients) found that routine rectal retroflexion had low yield for clinically important neoplasia after careful forward examination, detecting only one 4 mm tubular adenoma that was not visible on forward view 2. However, UK quality standards still recommend attempting retroflexion in 90% of cases 1, as the maneuver is safe, adds minimal time, and can detect lesions missed on forward view.

Safety Profile

• Estimated perforation risk: 0.01% 1
• Well-tolerated with no increase in patient discomfort 2, 3
• No complications reported in large prospective studies
• The maneuver is considered safe when performed by trained endoscopists

Quality Metrics

• Document whether rectal examination or retroflexion was performed or omitted in 100% of cases 1
• Target: Perform rectal retroflexion in 90% of colonoscopies 1
• This should be a routine part of colonoscopy training and practice