Examkin

Question

Difficulty: Very hardInterpreting Imaging Results

A 31-year-old man is brought to the trauma resuscitation bay following a high-speed motorcycle collision where he was thrown 30 feet. He is hemodynamically stable with a blood pressure of 118/78 mmHg and a heart rate of 105/min. His primary survey is intact. The secondary survey is notable for a mechanically unstable 'open book' pelvic fracture, significant perineal ecchymosis, and frank blood visible at the urethral meatus. A focused assessment with sonography for trauma (FAST) exam shows no free intraperitoneal fluid. Urinalysis from a spontaneously voided small sample prior to arrival showed gross hematuria.

Arrange the following diagnostic imaging steps in the correct mandated sequence to properly evaluate this patient's genitourinary injuries while minimizing iatrogenic harm and diagnostic artifact.

  1. 1Retrograde urethrography (RUG)
  2. 2Portal venous phase computed tomography (CT) of the abdomen and pelvis
  3. 3Delayed-phase (excretory) computed tomography of the urinary tract
  4. 4Computed tomography (CT) cystography with retrograde bladder instillation

Answer

The correct sequence is: Retrograde urethrography (RUG) → Portal venous phase CT of the abdomen and pelvis → Delayed-phase (excretory) CT → CT cystography.
The correct diagnostic pathway for complex genitourinary trauma must balance clinical safety with radiologic physics. Urethral integrity must be established first via Retrograde Urethrography (RUG) to prevent iatrogenic transection during catheterization. After safe catheter placement, standard trauma imaging (portal venous phase) evaluates the solid organs. The delayed (excretory) phase must follow to assess the ureters and collecting system. Finally, CT cystography is performed last; this requires retrograde distension of the bladder with contrast, which creates massive streak artifacts that would ruin the diagnostic quality of any subsequent pelvic scans if it were performed earlier.

Step-by-Step Solution

1
Perform Retrograde Urethrography (RUG)
Evaluates the integrity of the urethra.
Blood at the meatus and perineal ecchymosis in the setting of a pelvic fracture strongly suggest a urethral tear. Blind urethral catheterization is absolutely contraindicated as it can convert a partial tear into a complete transection.
2
Perform Portal Venous Phase CT
Evaluates solid organ parenchyma, including the kidneys, liver, and spleen.
Once the urethra is deemed intact and a catheter is placed, standard IV contrast trauma imaging is needed to evaluate the extent of the pelvic hematoma and check for renal parenchymal lacerations.
3
Perform Delayed-Phase (Excretory) CT
Highlights the renal collecting system and ureters.
Intravenous contrast requires 10 to 15 minutes to be filtered and excreted by the kidneys. The portal venous phase is completely insufficient for identifying urinary extravasation from caliceal or ureteral injuries.
4
Perform CT Cystography via retrograde filling
Evaluates for intraperitoneal or extraperitoneal bladder rupture.
Bladder rupture is highly associated with pelvic ring fractures. CT cystography requires instilling 350-400 mL of contrast retrogradely into the bladder. This must be the final imaging step because dense contrast pooling in the bladder causes severe radiologic streak artifacts that obscure adjacent pelvic structures, which would ruin the venous and delayed-phase scans if done earlier.

Key Concept

Genitourinary Trauma Imaging Sequencing
Rate this question

Topics

Interpreting Imaging Results

More questions from this topic