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Renal Trauma: Injury of the Kidney

Renal trauma is an injury to the renal parenchyma or vasculature by an outside force. Consequences of renal trauma are bleeding or damage to the collecting system with possible leakage of urine. EAU Guidelines: Urological Trauma. Review literature: (Diederichs and Mutze, 2003) (Kawashima et al., 2002) (Meria and Mazeman, 2000) (Vasile et al., 2000).

Epidemiology and Etiology

Blunt Trauma:

Blunt trauma is the most common etiology; direct blunt force (contusion, bruising of the abdomen or flank) leads to an injury of the kidney. In blunt abdominal trauma, up to 40% present with renal injury. In urban areas, 80% of renal injuries occur in the context of polytrauma.

Deceleration Trauma:

High-velocity accidents (falls from height oder motor vehicle accidents) damage the kidney, renal vessels or ureter by the inertia of the mass.

Penetrating Injuries:

Renal trauma due to gunshot or stab wounds are rare, they play a greater role in the U.S. than in Europe. Concomitant bowel lesions are present in 80% of cases.

Signs and Symptoms of Renal Trauma

Acute signs and symptoms:

• History of abdominal trauma or deceleration injury
• Bruising and hematoma of abdomen or flank
• Abdominal tenderness and tumor
• Flank pain
• Rib fracture
• Hematuria
• Hemodynamic instability, Shock

Late complications of renal trauma:

• Urinoma
• Renal Abscess
• Renal arteriovenous fistula
• Renal hypertension
• Hydronephrosis
• Loss of renal function

Diagnostic Workup of Renal Trauma

Laboratory examinations:

Urine sediment, blood count, creatinine. The lack of hematuria does not exclude severe renal trauma.

Ultrasound imaging:

Abdominal (renal) ultrasound is a valuable tool for the initial evaluation of abdominal injuries without clear evidence of renal injury. If free abdominal fluid, retroperitoneal hematoma, urinoma, hydronephrosis, or kidney infarction (with Doppler ultrasound) is seen, abdominal CT is necessary for an exact diagnosis.

Computed tomography:

CT scan is the imaging technique of choice if there is a high suspicion of renal injury: severe trauma, abnormalities in ultrasound imaging, or hematuria [fig. CT imaging of renal trauma]. Fill the bladder with contrast medium before CT to exclude bladder injury in blunt abdominal trauma.

Contraindication of CT: patients with hemodynamic instability after initial resuscitation and suspicion for intraabdominal bleeding. They require surgical intervention without further imaging.

CT imaging in renal trauma: left figure: renal trauma grade I (subcapsular hematoma). Right figure: renal trauma grade III (retroperitoneal hematoma, renal laceration >1 cm). With kind permission, Dr. G. Antes, Kempten.

Urography (IVP):

Intravenous urography is outdated and has been replaced by computed tomography. IVP may be helpful (as an alternative to CT) to exclude renal injury, e.g., patients with hematuria and normal ultrasound imaging, and if CT is not available. Urography also has a limited role in intraoperative imaging after emergency laparotomy (single shot IVP).

Classification (Severity) Of Renal Trauma

The severity of renal trauma is classified in five grades according to the American Association for the Surgery of Trauma (AAST), see fig. Classification of renal trauma for details.

AAST classification of renal trauma: in five grades (Kozar et al., 2018), advance one grade for bilateral injuries:
Grade I: renal contusion with hematuria or subcapsular hematoma.
Grade II: renal laceration of less than 1 cm, perirenal hematoma confined to the perirenal fascia without active bleeding.
Grade III: renal laceration of more than 1 cm, without urinary extravasation, active bleeding with perirenal hematoma confined to the perirenal fascia.
Grade IV: renal laceration extending through renal cortex, medulla and collection system with urinary extravasation, vascular injury to segmental renal artery or vein, segmental infarctions without associated active bleeding, active bleeding with hematoma extending beyond the perirenal fascia (into the retroperitoneum or peritoneum).
Grade V: completely shattered kidney, vascular injury of the renal hilum, devascularization of the complete kidney with active bleeding.

Treatment of Renal Trauma

Conservative management:

Conservative management is possible in renal trauma with stable circulation and trauma severity grade I–III (no urinary extravasation). Conservative management consists of bed rest until gross hematuria resolves and frequent monitoring of vital signs and blood count. Fever, dropping blood count or flank pain are indications for repeated imaging (ultrasonography or CT) or surgery.

Selective embolization:

Selective embolization is an option in case of persistent bleeding to avoid open surgery.

Internal ureteral stent:

Ureteral stenting is indicated for urinary extravasation in grade IV renal injury (MJ/DJ ureteral stent or percutaneous nephrostomy). Place a urethral catheter to prevent reflux alongside the DJ stent. Large (delayed diagnosed) urinomas are drained percutaneously in addition to ureteral stenting. Antibiotic prophylaxis is often recommended.

Surgical Management:

Absolute indications for surgery are:

• Hemodynamic instability after initial resuscitation
• Grade V renal injury with expanding renal hematoma
• Ureteropelvic junction disruption

Relative indications (depending on other factors):

• Urinary extravasation with nonviable renal tissue over 25%
• Associated intraabdominal injuries
• Gunshot wounds
• Suspicious intraoperative IVP during emergency laparotomy.

Surgical technique:

Transperitoneal exposure using a midline laparotomy, cell saver and packed red blood cells for transfusion should be ready. Early vascular control (near the aorta) before opening of renal fascia improves renal salvage rate. Renal reconstruction can be done with temporary ischemia. Kidney defects may be sutured (renorrhaphy) and covered with omentum majus, absorbable mesh or retroperitoneal fat. Hemostatic agents help control bleeding tissue. If necessary, insert a nephrostomy for urinary drainage.

Indications for nephrectomy:

• Extensive renal or vascular injury
• Ischemia of the kidney
• Hemodynamic instability due to bleeding

References

Kawashima u.a. 2002 KAWASHIMA, A. ; SANDLER, C. M. ; CORL, F. M. ; WEST, O. C. ; TAMM, E. P. ; FISHMAN, E. K. ; GOLDMAN, S. M.: Imaging evaluation of posttraumatic renal injuries.
In: Abdom Imaging
27 (2002), Nr. 2, S. 199–213

R. A. Kozar et al., “Organ injury scaling 2018 update: Spleen, liver, and kidney.,” The journal of trauma and acute care surgery, vol. 85, no. 6, pp. 1119–1122, 2018.

Meria und Mazeman 2000 MERIA, P. ; MAZEMAN, E.: Immediate and delayed management of renal trauma.
In: Eur Urol
37 (2000), Nr. 1, S. 121–30

Vasile u.a. 2000 VASILE, M. ; BELLIN, M. F. ; HELENON, O. ; MOUREY, I. ; CLUZEL, P.: Imaging evaluation of renal trauma.
In: Abdom Imaging
25 (2000), Nr. 4, S. 424–30

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