Is cystoscopy indicated in cases of suspected urinary tract injury following a saddle injury?

Cystoscopy for Suspected Urinary Tract Injury Following Saddle Injury

Cystoscopy is indicated in cases of suspected urinary tract injury following a saddle injury, particularly when there are signs of urethral trauma such as blood at the urethral meatus, perineal hematoma, or difficulty with urinary catheterization.

Diagnostic Approach for Saddle Injuries

Saddle injuries present a high risk for urethral trauma compared to other mechanisms of pelvic injury. Research shows that urethral injury rates are significantly higher in saddle horn injuries (83%) compared to other mechanisms of pelvic trauma (49%) 1.

Initial Evaluation

1. Assess for signs of urethral injury:

   • Blood at the external urethral meatus
   • Perineal laceration or hematoma
   • Scrotal hematoma
   • Urinary retention
   • Difficulty or inability to insert a urinary catheter
   • Suprapubic fullness
   • Superiorly displaced prostate on rectal examination 2, 3

2. Hematuria assessment:

   • Gross hematuria in the setting of pelvic trauma strongly suggests urinary tract injury
   • In one study, 29 of 32 patients with urological injuries had gross hematuria 4
   • Microscopic hematuria alone has a low correlation with serious urological injury 4

Diagnostic Imaging Algorithm

For Hemodynamically Stable Patients:

1. First-line imaging: Retrograde urethrography (RUG)

   • RUG is the gold standard for diagnosing traumatic urethral injuries 2, 3
   • Should be performed BEFORE attempting urinary catheterization in suspected cases 3
   • Sensitivity of 89% and specificity of 97% compared to cystourethroscopy 3
   • Extravasation of contrast indicates urethral injury 3

2. Cystoscopy indications:

   • When RUG shows evidence of urethral injury
   • When RUG is inconclusive but clinical suspicion remains high
   • As a complementary procedure to RUG for better visualization
   • In cases with associated penile injuries (preferred over RUG) 3
   • Flexible cystourethroscopy can provide both diagnostic information and therapeutic intervention 5

3. CT cystography:

   • For suspected bladder injuries (often coexisting with urethral trauma)
   • Conventional or CT cystography has similar sensitivity (95%) and specificity (100%) 2
   • CT with delayed phase is less sensitive than retrograde cystography for bladder injuries 2

For Hemodynamically Unstable Patients:

• Postpone urethral investigations
• Insert suprapubic catheter if urinary drainage is needed 3
• Consider intravenous urography during emergency surgery if CT is unavailable 2

Clinical Pearls and Pitfalls

Pearls:

• Saddle injuries have a significantly higher rate of urethral trauma (83%) and pubic symphysis diastasis (100%) compared to other pelvic trauma mechanisms 1
• Direct inspection of the bladder should be performed during emergency laparotomy when bladder injury is suspected 2
• Methylene blue or indigo carmine can be useful during cystoscopy to identify subtle injuries 2, 6

Pitfalls:

• Never attempt blind catheterization when urethral injury is suspected as this may worsen the injury 3
• CT scanning alone may miss urethral injuries - in one study, only 1 of 3 posterior urethral injuries was detected with CT 7
• Passive bladder distension with contrast during CT by clamping a urinary catheter is not effective due to low intravesical pressure 2
• Excessive pressure during contrast injection for RUG can lead to complications including extravasation, bacteremia, and sepsis 3

Conclusion

For suspected urinary tract injuries following saddle trauma, a systematic approach using retrograde urethrography followed by cystoscopy when indicated provides the most accurate diagnosis and guides appropriate management. The high incidence of urethral trauma in saddle injuries warrants a high index of suspicion and thorough evaluation.