Urinary Tract Injuries: A Comprehensive MCCQE1 Guide

Introduction

Urinary tract injuries are a high-yield topic for the MCCQE1. As a future Canadian physician, you must be adept at recognizing these injuries in the context of trauma (blunt and penetrating) and iatrogenic causes. This guide aligns with the CanMEDS roles, particularly Medical Expert (diagnostic reasoning and management) and Collaborator (consulting Urology).

In the Canadian context, blunt trauma (motor vehicle collisions, winter sports like skiing/snowmobiling) accounts for the vast majority of urinary tract injuries compared to penetrating trauma.

Renal Trauma

The kidney is the most commonly injured genitourinary organ.

Mechanism of Injury

• Blunt Trauma (80-90%): MVA, falls, sports (hockey, football).
• Penetrating Trauma: Stabbings, gunshot wounds (less common in Canada but increasing in urban centers).

Clinical Presentation

• Flank pain or ecchymosis (Grey Turner’s sign).
• Hematuria (Gross or Microscopic).
• Associated injuries: Rib fractures (lower ribs), vertebral fractures.

Indications for Renal Imaging (CT with IV Contrast)

According to Canadian trauma guidelines and ATLS principles, imaging is indicated in:

1. Penetrating trauma with any degree of likelihood of renal damage.
2. Blunt trauma with:
   • Gross hematuria.
   • Microscopic hematuria AND shock (SBP < 90 mmHg).
   • Rapid deceleration injury (suspect pedicle injury).
3. Pediatric patients: Any degree of hematuria (kidneys are larger relative to body size and less protected).

AAST Renal Injury Grading Scale

Management Principles

Ureteral Injuries

Ureteral injuries are rare in external trauma but are a common source of litigation in iatrogenic cases.

Etiology

• Iatrogenic (Most Common): Gynecologic surgery (hysterectomy), Colorectal surgery, Ureteroscopy.
• Trauma: Penetrating trauma (GSW). Rare in blunt trauma (requires hyperextension).

Diagnosis

Often delayed. Suspect if:

• Persistent ileus.
• Fever/Sepsis post-op.
• Watery discharge from drain or vagina.
• Rising creatinine (if bilateral or solitary kidney).

Diagnostic Test of Choice: CT Urogram (delayed phase) or Retrograde Pyelogram.

Bladder Injuries

Bladder injuries are strongly associated with pelvic fractures.

Classification & Management

Understanding the distinction between Intraperitoneal and Extraperitoneal rupture is vital for the MCCQE1.

Urethral Injuries

Anterior vs. Posterior Urethra

1. Posterior Urethral Injury:

   • Associated with Pelvic Fractures.
   • Injury at the membranous urethra (prostatomembranous junction).
   • Clinical Triad:
     1. Blood at the urethral meatus.
     2. Inability to void.
     3. Palpably distended bladder.
   • Note on DRE: A “high-riding prostate” is a classic sign but is unreliable and often difficult to appreciate.

2. Anterior Urethral Injury:

   • Associated with Straddle Injuries (falling onto a bike bar or fence) or perineal trauma.
   • Injury to the bulbar urethra.
   • Signs: Perineal hematoma (“butterfly” pattern if Buck’s fascia remains intact).

Diagnostic Algorithm

Canadian Guidelines & Clinical Pearls

CUA & Trauma Guidelines

• FAST Exam: Focused Assessment with Sonography for Trauma. Useful for detecting intraperitoneal fluid but poor sensitivity for retroperitoneal (renal) injuries.
• Hematuria in Canada: The Canadian Urological Association (CUA) has specific guidelines for microhematuria. In trauma, however, stick to the shock/mechanism rules listed in the Renal Trauma section.

Important Mnemonics

“Blood at the Meatus means Stop the Apparatus”

• Refers to the contraindication of Foley catheterization in suspected urethral injury.

“Dome for the Home”

• Intraperitoneal bladder rupture occurs at the Dome and requires surgery (go Home implies leaving the ED for the OR).

Key Points to Remember for MCCQE1

• Hemodynamic stability dictates management in renal trauma.
• CT with IV contrast (delayed phase) is the gold standard for renal/ureteral imaging.
• Retrograde Urethrogram is the first step for suspected urethral injury.
• Intraperitoneal bladder rupture = Surgery.
• Extraperitoneal bladder rupture = Catheter.
• Pelvic fracture + gross hematuria $\rightarrow$ High suspicion for bladder/urethral injury.

Sample Question

Clinical Scenario

A 24-year-old male is brought to the Emergency Department following a high-speed motorcycle collision. He complains of severe pelvic pain and an inability to void. His vitals are HR 110 bpm, BP 100/60 mmHg. On examination, there is instability of the pelvic ring upon compression. Inspection of the perineum reveals bruising, and there is blood visible at the urethral meatus. A FAST scan is negative for free fluid.

Which one of the following is the most appropriate next step in management?

• A. Attempt gentle insertion of a 16 Fr Foley catheter
• B. Perform a CT abdomen/pelvis without contrast
• C. Perform a retrograde urethrogram
• D. Place a suprapubic catheter immediately
• E. Perform flexible cystoscopy

Explanation

The correct answer is:

• C. Perform a retrograde urethrogram

Detailed Analysis

Why C is correct: The patient presents with a classic mechanism (motorcycle crash, pelvic fracture) and clinical signs (blood at the meatus, inability to void) suggestive of a posterior urethral injury. The presence of blood at the meatus is an absolute contraindication to blind urethral catheterization. The diagnostic gold standard to assess urethral integrity is a Retrograde Urethrogram (RUG).

Why A is incorrect: Attempting to insert a Foley catheter in the presence of a potential urethral disruption can convert a partial tear into a complete transaction and introduce infection into the retropubic hematoma.

Why B is incorrect: While a CT is indicated for the trauma workup, specifically for the urethral issue, a CT without contrast will not delineate the urethral injury. A CT Cystogram or Urogram might be used later, but RUG is the immediate specific test for the urethra.

Why D is incorrect: While a suprapubic catheter may be the ultimate management if a tear is confirmed, it is an invasive procedure. One must first confirm the diagnosis with a RUG. Furthermore, if the bladder is not distended or easily palpable, blind suprapubic insertion carries risks.

Why E is incorrect: Flexible cystoscopy is generally not the first-line screening tool in the acute trauma bay for this indication compared to the speed and safety of a RUG.

References

1. Medical Council of Canada. MCCQE Part I Clinical Decision-Making and Multiple-Choice Question Objectives. Available at: mcc.ca 
2. Canadian Urological Association (CUA). Guidelines on the Management of Trauma.
3. Advanced Trauma Life Support (ATLS). Student Course Manual. 10th Edition. American College of Surgeons.
4. Campbell-Walsh-Wein Urology. 12th Edition. Elsevier.
5. Morey, A. F., et al. (2020). Urotrauma: AUA Guideline. Journal of Urology.