When is a retrograde urethrogram (RUG) indicated?

Indications for Retrograde Urethrogram (RUG)

Retrograde urethrography should be performed in patients with suspected urethral injury, particularly those with blood at the urethral meatus after pelvic trauma, before attempting any urinary catheterization. 1

Primary Indications

• Suspected urethral trauma:

  • Blood at the external urethral meatus 1, 2
  • Pelvic fracture with associated signs of urethral injury 1
  • Perineal/scrotal hematoma 1, 2
  • Suprapubic fullness 1, 2
  • Urinary retention 1, 2
  • Difficulty or inability to insert a urinary catheter 1, 2
  • Superiorly displaced or non-palpable prostate on rectal examination 1, 2
  • Straddle injuries 2

• Evaluation of urethral strictures 3, 4

  • Though urethroscopy may be more accurate in some cases 4

• Post-surgical evaluation of the urethra 3

Clinical Decision Algorithm

1. For trauma patients:

   • If blood is present at the urethral meatus → Perform RUG before any catheterization attempt 1
   • If pelvic fracture is present with clinical signs of urethral injury → Perform RUG 1
   • If hemodynamically unstable → Postpone RUG and place suprapubic catheter 1, 2

2. For non-trauma patients:

   • If urethral stricture is suspected → Consider RUG, though combining with urethroscopy improves diagnostic accuracy 4
   • If post-surgical evaluation of urethra is needed → RUG is appropriate 3

Special Considerations

• In penile injuries: Urethroscopy is preferred over RUG 1, 2
• In female patients: Due to short urethra, urethroscopy is recommended over RUG 1, 2
• In children: RUG remains the study of choice for suspected urethral trauma, with catheter size adjusted by age 3
• During emergency laparotomy: If urethral injury is suspected, direct investigation is preferred when feasible 1

Technical Aspects

RUG should be performed by:

• Positioning the patient obliquely with bottom leg flexed and top leg straight 1
• If severe pelvic or spine fractures are present, patient may remain supine 1
• Using a 12Fr Foley catheter or catheter-tipped syringe introduced into the fossa navicularis 1
• Placing the penis on gentle traction 1
• Injecting 20 mL of undiluted water-soluble contrast material 1

Interpretation

• Extravasation of contrast indicates urethral injury 1, 2
• Incomplete lesions: Extravasation of contrast with bladder filling 1, 2
• Complete lesions: Extravasation of contrast without bladder filling 1, 2

Pitfalls and Complications

• Blind catheter passage prior to RUG should be avoided to prevent worsening injury 1
• Excessive pressure during contrast injection can lead to extravasation or intravasation, risking bacteremia, sepsis, contrast reactions, and worsening of strictures 5
• If a Foley catheter has already been placed, a pericatheter RUG can be performed using a 3Fr catheter or angiocatheter held in the fossa navicularis 1

RUG remains the gold standard for diagnosing traumatic urethral injuries with high sensitivity for detecting urethral disruption, though it should be used judiciously and with proper technique to avoid complications.