Retrograde Urethrography: The Gold Standard for Urethral Evaluation
Retrograde urethrography (RUG) is the procedure of choice and must be performed before any urethral catheterization or manipulation when urethral injury is suspected. 1
When to Perform RUG
Perform RUG immediately in patients presenting with:
- Blood at the urethral meatus (the most critical indicator) 1, 2
- Pelvic fractures with hematuria 1
- Straddle injuries 1
- Perineal or scrotal hematoma 1
- Superiorly displaced or non-palpable prostate on rectal examination 1
- Difficulty or inability to insert urinary catheter 1
- Urinary retention with trauma history 1
Critical Timing and Sequencing
Never attempt urethral catheterization before obtaining RUG when urethral injury is suspected - this can convert partial injuries to complete transections and cause long-term complications including strictures, impotence, and incontinence. 1, 2
The proper sequence is:
- Clinical examination identifying concerning signs
- RUG to document urethral integrity
- Only then proceed with catheterization if urethra is intact 1
Technical Approach
RUG demonstrates 89% sensitivity and 97% specificity compared to cystourethroscopy. 3 The procedure involves:
- External application of contrast without urethral instrumentation (preferred modern techniques use vacuum devices or clamp methods to avoid iatrogenic injury) 4, 5
- Water-soluble contrast agent administration 3
- Fluoroscopic imaging to visualize contrast extravasation 1
Extravasation of contrast indicates urethral injury - incomplete lesions show extravasation with bladder filling, while complete lesions show extravasation without bladder filling. 1
Alternative Diagnostic Modalities
Flexible urethroscopy is preferred over RUG specifically for penile injuries and in female patients due to the short female urethra. 1, 2
Ultrasound urethrography can provide superior information about stricture length, lumen caliber, and spongiofibrosis extent compared to radiologic urethrography, though it is not the standard for acute trauma. 6, 7
Common Pitfalls to Avoid
- Never perform blind catheterization in trauma patients with blood at meatus - this is the most common error that worsens outcomes 2
- Do not rely on CT cystography alone for urethral evaluation - it misses urethral injuries 1
- Avoid repeated catheterization attempts, which extend injury 2
- In hemodynamically unstable patients, defer RUG and place suprapubic catheter for drainage 1
Special Populations
In pediatric patients, RUG uses appropriately sized catheters (5 Fr for infants <1 year, 7 Fr for ages 1-5 years, 8 Fr for >5 years) and can be combined with voiding cystourethrography when indicated. 3
For pregnant women or when radiation exposure is concerning, MRI can be used for delayed evaluation, though not in acute trauma settings. 1