Imaging Methods
The choice of imaging modality depends on the patient's condition and the suspected site of injury. Intravenous urography is no longer used in modern emergency practice.
- MSCT (multislice CT): The absolute standard for acute trauma. Intravenous contrast administration and multiplanar reconstruction allow for the evaluation of both parenchymal organs and the urinary tract, as well as the detection of intra-abdominal injuries. Accurate CT staging frequently allows patients to be managed conservatively.
- Ultrasound (including FAST protocol): Optimal for rapidly detecting free fluid. Well-suited for evaluating scrotal and penile injuries and for serial monitoring of renal trauma, but has low sensitivity for primary diagnosis of renal injuries (except in pediatric patients) and poor visualization of the retroperitoneum.
- MRI: Due to scan duration, it is unsuitable for the acute phase of polytrauma. However, it is indispensable for the detailed evaluation of penile, testicular, and urethral ruptures.
Renal injuries
Renal injuries account for one-tenth of all abdominal trauma. The vast majority (90%) are blunt injuries resulting from motor vehicle accidents or falls. The remaining 10% are penetrating (stab, gunshot) and iatrogenic injuries.
Risk factors: Children are particularly vulnerable: their kidneys are larger relative to body size, more mobile, their ribs are softer, and the perirenal fat capsule is thin. Patients with congenital anomalies (horseshoe kidney, cysts, tumors) are also at increased risk. If the severity of the injury on CT is disproportionate to the force of impact, an underlying pathology should be suspected.
Mechanisms of blunt trauma:
- Compression between the ribs and the spine causes contusions and parenchymal lacerations.
- Rapid deceleration (motor vehicle collisions) leads to organ displacement and avulsion at the pelviureteric junction (pelviureteric junction).
- Stretching of the vascular pedicle causes intimal tears, thrombosis, or complete vascular avulsion.
Penetrating injuries are associated with injuries to other organs in 80% of cases and more frequently require surgery. However, in hemodynamically stable patients, MSCT allows for consideration of conservative management.
Bladder injuries
CT cystography is used for diagnosis. It is performed in patients with gross hematuria in the setting of pelvic fractures or free fluid. Important: urethral injury must be ruled out prior to catheter placement.
To ensure an adequate examination, the bladder must be distended: up to 400 mL of 4% contrast is administered by drip infusion. Standard CT with a clamped urinary catheter is inadequate—it yields false-negative results.
Types of rupture on CT:
- Extraperitoneal: Contrast extravasates into the prevesical space of Retzius, inguinal regions, and thighs. The extravasate often has a "flame-shaped" or "molar tooth" appearance. Frequently associated with posterior urethral rupture (posterior urethra).
- Intraperitoneal: The defect is typically located at the dome. Less dense (urine-diluted) contrast outlines the bowel loops.
- Combined: Occurs in 5–10% of cases, combining features of both types.
Male genital trauma
A classic example of an urgent pathology is penile fracture, which occurs during sexual intercourse. MRI is the imaging modality of choice in this case. T2-weighted images clearly demonstrate a defect (tear) of the tunica albuginea (tunica albuginea) and the adjacent corpus cavernosum tissue (corpus cavernosum).
Briefly: answers to topical questions
What are the grades of renal injury according to the AAST classification?
According to the AAST classification, renal injuries are graded I–V.
- Grade II (Grade II) — non-contained perinephric hematoma (perinephric haematoma) with ill-defined margins.
- Grade III (Grade III) — renal parenchymal laceration (laceration) >1 cm in depth, not involving the collecting system.
- Grade IV (Grade IV) — parenchymal laceration extending into the urinary collecting system with urinary extravasation (urinary extravasation); segmental or main renal artery/vein injury with contained hemorrhage; renal pelvis laceration (renal pelvis laceration); or complete ureteropelvic junction disruption.
- Grade V (Grade V) — shattered kidney (shattered kidney) or renal pedicle avulsion (avulsion of renal hilum) resulting in renal devascularization.
Grade I criteria are not described in the provided sources.
What are the indications for emergency surgical intervention in renal trauma?
The primary indication for emergency surgical intervention in renal trauma is hemodynamic instability of the patient.
- Renal vascular avulsion — requires emergency surgery as it is accompanied by hemodynamic instability.
- Active hemorrhage — surgical exploration (surgical exploration) is necessary in the presence of concurrent hemodynamic instability.
- Resuscitation failure — hemodynamically unstable patients who fail to respond to rapid resuscitation are taken directly to the operating room, bypassing diagnostic imaging.
What CT signs are characteristic of renal vascular pedicle injury?
The following CT signs are characteristic of renal vascular pedicle injury:
- Devascularization — absence of parenchymal enhancement and reduced perfusion, while the kidney often appears morphologically intact.
- Rim sign (rim sign) — preserved peripheral enhancement due to intact collateral blood flow.
- Size alteration — reduction in size of the unperfused kidney.
- Vascular defects — abrupt cut-off (abrupt cut-off) of the proximal renal artery visualized on multiplanar reconstruction.
- Hematoma — presence of an extensive retroperitoneal hematoma or a small perivascular hemorrhage.
The CT appearance of an extraperitoneal bladder rupture resembles a "flame" or a "molar tooth".
Class and exam questions
Should a CT scan be performed in a patient with severe abdominal trauma if their hemodynamics are unstable?
No. Hemodynamically unstable patients who do not respond to resuscitation measures should be taken directly to the operating room, bypassing diagnostic imaging.
Is 200 mL of contrast sufficient for performing MSCT cystography?
No, administering less than 250 mL of contrast may lead to a false-negative result due to inadequate distension of the bladder wall. The standard volume is up to 400 mL.
What do blood clots emerging from the ureteral orifices into the urinary bladder indicate?
Such intravesical blood clots indicate upper urinary tract injury (renal or ureteral trauma) rather than a direct rupture of the bladder itself.
What else to study on this topic
- Peculiarities of diagnostic imaging in pediatric urological trauma.
- MRI diagnosis of urethral injuries in pelvic bone fractures.
- Indications for conservative management of penetrating renal injuries.
- The use of total-body scanning protocols (pan-scan) in blunt polytrauma.
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