What are the preparation and procedure guidelines for a Micturating Cysto-Urethrogram (MCU)?

Micturating Cysto-Urethrogram (MCU) Procedure Guidelines

The preparation for MCU should include proper patient education, antibiotic prophylaxis when indicated, and sterile catheterization technique, while the procedure involves controlled bladder filling with contrast media followed by imaging during voiding to evaluate the lower urinary tract.

Patient Preparation

• Pre-procedure education: Explain the procedure to the patient or parents/guardians to reduce anxiety and improve cooperation
• Antibiotic prophylaxis: Consider prophylactic antibiotics for patients with specific risk factors (e.g., known vesicoureteric reflux, recurrent UTIs)
• Timing after UTI: MCU can be performed as soon as acute inflammation has subsided (typically after 1 week from diagnosis), contrary to the traditional belief that it should be delayed 4-6 weeks 1, 2
• Contraindications: Active urinary tract infection, urethral trauma, or severe urethral stricture

Equipment and Materials

• Fluoroscopy equipment with capability for dynamic imaging
• Appropriate-sized urinary catheter:
  • For pediatric patients: 5Fr for infants, 7Fr for ages 1-5, and 8Fr for older than 5 years 3
  • For adults: 12-16Fr catheter
• Sterile catheterization kit
• Contrast media (water-soluble iodinated contrast)
• Sterile drapes and personal protective equipment

Procedure Steps

1. Patient positioning: Place patient in supine position on fluoroscopy table

2. Sterile preparation: Clean external genitalia with antiseptic solution

3. Catheterization:

   • Perform gentle urethral catheterization using sterile technique
   • Important: In cases of suspected urethral injury (perineal hematoma, blood at meatus, pelvic fracture), perform retrograde urethrography (RUG) before catheterization 4, 3
   • For males with suspected urethral injury, avoid blind catheter passage 3

4. Contrast administration:

   • Empty bladder completely through catheter
   • Fill bladder with contrast media under gravity (height 60-100 cm above pubic symphysis)
   • Fill until patient reports fullness or discomfort, or until adequate bladder distension is achieved
   • Caution: Avoid excessive pressure during contrast injection to prevent complications such as extravasation, bacteremia, or worsening of strictures 3

5. Imaging acquisition:

   • Obtain images during filling phase to assess bladder contour and detect vesicoureteric reflux
   • Remove catheter (unless contraindicated)
   • Obtain images during voiding phase to evaluate:
     • Bladder emptying
     • Urethral anatomy
     • Vesicoureteric reflux during increased intravesical pressure

6. Post-procedure care:

   • Monitor for signs of infection or urinary retention
   • Encourage fluid intake to help flush contrast media

Special Considerations

• For suspected urethral trauma: Perform retrograde urethrography (RUG) before attempting catheterization 4, 3
• For pelvic trauma patients: If hemodynamically unstable, postpone urethral investigations and insert a suprapubic catheter for urinary drainage 3
• For pediatric patients: Use age-appropriate catheter sizes and consider sedation for young children 3
• For pregnant women and elderly patients: Position pelvic binders cautiously if used 4

Interpretation Guidelines

• Contrast extravasation during RUG indicates urethral injury 3:
  • Extravasation with bladder filling = incomplete lesion
  • Extravasation without bladder filling = complete lesion
• Vesicoureteric reflux grading should be documented when present
• Bladder contour abnormalities should be noted

Common Pitfalls and Caveats

• Technique variations can significantly affect detection of vesicoureteric reflux 5
• False-positive reflux may occur if performed within one week of acute UTI 1
• Inadequate bladder filling may lead to false-negative results for reflux
• Passive bladder distension with contrast during CT by clamping a urinary catheter is ineffective due to low intravesical pressure 4
• MCU may not be necessary in children over 6 months with UTI if IVU is normal 6

By following these standardized guidelines, clinicians can maximize the diagnostic yield of MCU while minimizing patient discomfort and potential complications.