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Renal Trauma: Injury of the Kidney

Renal trauma is an injury to the renal parenchyma, collecting system, or renal vascular system caused by blunt or penetrating external force. Consequences include hemorrhage, ischemia of the renal tissue, or damage to the urinary tract with possible urinary extravasation or urinary outflow obstruction.

AAST classification of renal trauma into five grades: modified according to Kozar et al., 2018. See text for details.

Epidemiology and Etiology

Blunt injuries:

Renal injury most commonly results from direct blunt force (compression or contusion), usually in the setting of motor vehicle accidents, falls, or sports injuries. In blunt abdominal trauma, the kidneys are involved in up to 10 % of cases.

Deceleration injury:

Injury to the renal pedicle or ureter, up to and including complete avulsion, caused by the inertia of the renal mass during a fall from a great height or a motor vehicle accident.

Penetrating injuries:

Gunshot or stab wounds are uncommon; they play a greater role in the United States than in Europe. Associated intra-abdominal injuries are common.

Signs and Symptoms

Acute signs and symptoms:

History of a compatible mechanism of injury (deceleration, flank contusion, penetrating injury), flank bruising and hematoma, flank pain, guarding and a palpable mass, rib fracture, hematuria, and signs of hemorrhagic shock.

Late complications:

Abscess, urinoma, urinary tract obstruction, arteriovenous fistula, renal hypertension, and loss of renal function due to hydronephrosis or renal artery stenosis.

Diagnosis

Laboratory examinations:

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

Abdominal ultrasound:

Abdominal ultrasound is a valuable tool for the initial evaluation of abdominal injuries without clear evidence of organ injury. If abnormalities are detected on ultrasound (hematoma, free fluid, hydronephrosis, urinoma, or perfusion abnormalities on Doppler ultrasound), abdominal CT is necessary for an exact diagnosis.

Computed tomography:

CT is the imaging technique of choice if there is a high suspicion of organ injury, including multiple trauma, penetrating injuries, deceleration injury, multiple rib fractures, abnormal ultrasound findings, or gross hematuria. Fill the bladder with contrast medium before the examination when injury to the lower urinary tract must be assessed.

Contraindication to CT: Patients with hemodynamic instability after initial resuscitation and suspicion of intra-abdominal bleeding should undergo laparotomy without further imaging.

CT imaging in renal trauma: Left image: grade I injury of the left kidney (subcapsular hematoma). Right image: grade III injury of the right kidney (retroperitoneal hematoma, renal parenchymal laceration >1 cm deep). With kind permission, Dr. G. Antes, Kempten.

Urography (IVP):

Urography has been almost completely replaced by CT. It is an option to exclude renal injury, for example in patients with hematuria and normal ultrasound findings when CT is not available. Urography also has a limited role in intraoperative imaging during emergency laparotomy (single-shot IVP).

Classification of Renal Injuries

The severity of renal trauma is classified into five grades according to the American Association for the Surgery of Trauma (AAST); see AAST classification. In bilateral renal injuries, the severity grade is increased by one grade.

Grade I:

Renal contusion with hematuria and/or subcapsular hematoma; the renal capsule is intact.

Grade II:

Superficial renal parenchymal laceration (<1 cm) and/or hematoma confined to the space within the renal fascia. No evidence of active bleeding.

Grade III:

Deeper renal parenchymal laceration (>1 cm) without urinary extravasation. Signs of active bleeding may be present as long as the hematoma remains confined within the renal fascia.

Grade IV:

Parenchymal laceration with collecting-system injury and urinary extravasation. Injury to a segmental renal vessel, possibly with segmental loss of function. Bleeding with extension of the hematoma beyond the perirenal compartment.

Grade V:

Completely shattered kidney. Injury to the hilar vessels. Complete loss of renal perfusion with active bleeding.

Treatment

Conservative management:

Appropriate for renal trauma below grade IV without urinary extravasation in patients with a stable or stabilizable circulation. Bed rest until the urine clears and close monitoring of vital signs and blood count are important. A falling hemoglobin level, flank pain, and fever are indications for repeat imaging with ultrasonography or, if necessary, CT.

Selective embolization:

Indicated in hemodynamically stable patients with significant active bleeding on imaging. The aim is to reduce blood loss and avoid renal exploration or nephrectomy.

Ureteral stenting and drainage:

Placement of an MJ/DJ ureteral stent or nephrostomy. This is indicated in significant urinoma formation; small urinary extravasations may be observed with further imaging follow-up. Large urinomas diagnosed with delay are drained percutaneously, with additional ureteral stenting. Prophylactic antibiotic therapy is often recommended. Placement of an indwelling urethral catheter reduces reflux and thus urinary extravasation.

Surgical exploration:

Indications:

Hemodynamic instability due to renal bleeding, grade V renal injury with an expanding retroperitoneal hematoma, traumatic separation of the ureter and renal pelvis, associated intra-abdominal injuries, or gunshot wounds.

Technique:

Transperitoneal renal exploration with cell-saver and transfusion capability, with rapid control of the vascular pedicle. During temporary ischemia, attempt hemostasis if the kidney is salvageable. Cover renal defects with absorbable mesh, peritoneum, or omentum majus. If necessary, establish urinary drainage with a nephrostomy.

Indications for nephrectomy:

Complete renal disruption, pedicle avulsion without a reconstructive option, complete renal ischemia, or hemodynamic instability due to active renal bleeding.

References

EAU Guidelines: Urological Trauma.

Diederichs und Mutze 2003 DIEDERICHS, W. ; MUTZE, S.: [Renal trauma: is open surgery still up to date?].
In: Urologe A
42 (2003), Nr. 3, S. 322–7

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

  Deutsche Version: Nierentrauma

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