What are the distinguishing features between anterior and posterior urethral (urinary tract) injuries?

From the Guidelines

Distinguishing between anterior and posterior urethral injuries relies primarily on the anatomical location relative to the urogenital diaphragm, with anterior injuries involving the bulbar and penile urethra, and posterior injuries affecting the prostatic and membranous urethra, as outlined in the 2019 kidney and uro-trauma guidelines by the WSES-AAST 1.

Key Diagnostic Approaches

The key diagnostic approach includes:

• Physical examination
• Retrograde urethrography
• Assessment of associated injuries On examination, anterior injuries typically present with:
• Blood at the urethral meatus
• Penile or perineal bruising
• Sometimes a "high-riding" prostate on rectal exam if there's significant swelling Posterior injuries often accompany pelvic fractures and may present with:
• Perineal hematoma
• Inability to void
• Blood at the meatus

Diagnostic Tests

Retrograde urethrography is the gold standard diagnostic test, with:

• Anterior injuries showing contrast extravasation in the penile or bulbar region
• Posterior injuries demonstrating contrast extravasation at or above the urogenital diaphragm with possible disconnection between the prostatic and bulbar urethra, as noted in the 2019 guidelines by the WSES-AAST 1 The mechanism of injury also helps differentiate, with:
• Anterior injuries commonly resulting from straddle injuries or direct trauma to the penis
• Posterior injuries typically occurring with pelvic fractures or severe pelvic trauma, as discussed in the 2014 urotrauma guidelines by the AUA 1 This distinction is crucial as management differs significantly between the two types of injuries, with the 2019 WSES-AAST guidelines recommending conservative treatment for blunt anterior urethral injuries and delayed surgical repair for posterior urethral injuries 1

From the Research

Distinguishing between Anterior and Posterior Urethral Injuries

To distinguish between anterior and posterior urethral injuries, several factors and diagnostic methods can be considered:

• Mechanism of Injury:
  • Anterior urethral injuries are usually iatrogenic during catheterization or cystoscopy, or caused by blunt trauma, such as straddle injury or penetrating trauma 2, 3.
  • Posterior urethral injuries are most often caused by traffic accidents and are associated with pelvic fractures 2, 3.
• Diagnostic Methods:
  • Both types of injuries can be diagnosed using ascending urethrography, voiding cysto-urethrography, and urethroscopy/endoscopy 2.
  • Computed Tomography (CT) scans can also be used to evaluate urethral injuries, especially in cases of pelvic fractures 4, 5.
• CT Signs:
  • Specific CT findings such as elevation of the prostatic apex, extravasation of urinary tract contrast material above or below the urogenital diaphragm (UGD), and distortion or obscuration of the UGD fat plane can indicate posterior urethral injuries 4.
• Classification and Treatment:
  • The classification of urethral injuries is crucial for appropriate management, with different treatment approaches for anterior and posterior injuries 3, 6.
  • Treatment for posterior injuries may include cystostomy, abdominal drainage, perineal drainage, and urethra reconstruction, while anterior injuries may be managed conservatively or surgically 2, 6.