Renal Trauma

Genitourinary Tract Trauma

The genitourinary tract is involved only in 3% of pediatric trauma cases. However, the management of these injuries can be challenging.

Incidence

Almost 50% of genitourinary tract injuries involve the kidney. 90 % of renal injuries in children are due to blunt force trauma and approximately 10% of pediatric blunt abdominal trauma causes injury to the kidney. In four of five cases of renal trauma, other organs are also injured. The pediatric kidney is at greater risk for injury since:

* it is located lower in the abdomen

* it is not protected by the rib cage and the cupola of the diaphragm

* there is a dearth of protective perirenal tissue and fat.

An associated abnormality, congenital (ureteropelvic junction obstruction, ectopic kidney) or otherwise (Wilms' tumor), makes it even more susceptible to injury.

Blunt trauma resulting in renal contusion is the most common injury; however, the incidence of penetrating trauma is rising in children. Renal injury occurs in about 3% to 6% of patients with penetrating trauma.

Presentation

Patients present with flank pain and hematuria (microscopic or gross). Abdominal tenderness, flank mass, flank hematoma and fractured ribs are important signs of renal trauma. The degree of hematuria does not always correlate with the severity of the injury and children with renal pedicle injuries and/or pedicle disruptions may present without hematuria.

Classification

In 1989, the American Association for the Surgery of Trauma (AAST) Organ Injury Scaling Committee devised and pub­lished a classification or grading system for genitourinary tract injuries (Table 8.5, Image 8.8) to standardize injury descriptions for research and data collection purposes.

Table 8.5

Contusions are typically grade I or II.

For the kidney, this grading system has proved highly applicable, and its usefulness as a measure of the seriousness of renal injury and as a predictor of clinical outcomes.

For example, patients with a grade I injury require observation only, whereas those with a grade V injury are more likely to require nephrectomy. Those with intermediate injuries (grades II to IV) require individualized therapy, with a trend toward more invasive therapy as injury grade increases.

Note! It should be noted, however, these validation studies were composed primarily of adult patients. Thus extrapolation of results may not be entirely applicable to children.

Image 8.10 The AAST grading of renal injury. (A) Grade I, subcapsular hematoma (arrow). (B) Grade II, cortical laceration less than 1 cm deep (arrow) and perinephric hematoma (arrowhead). (C) Grade III, cortical laceration more than 1 cm deep (arrows) and perinephric hematoma. (D) Grade IV, laceration extending through the renal cortex, medulla (arrows), and collecting system (curved arrow). (E) Grade IV, segmental infarction caused by thrombosis of segmental renal artery branches (arrows). (F) Grade V, shattered kidney. (G) Grade V, avulsion of renal hilum that devascularizes the kidney.

Diagnosis

The most sensitive and specific test to evaluate renal trauma is computed tomography with intravenous contrast. If the patient is unstable or requires immediate surgery, a "one shot" intravenous pyelogram is performed by administering a 2 mL/kg bolus of radiographic contrast and obtaining a single supine radiograph of the abdomen 10 minutes later. This abbreviated study is sufficient to provide information regarding the kidney suspected of injury and of contralateral renal function.

Management

Blunt Injuries:

Nonoperative management of blunt renal trauma is as successful as nonoperative mangement of injuries to other solid organs, such as the liver and spleen.

Nonoperative management of hemodynamically stable children with blunt renal injury has become the standard of care in most centers, with success rates up to 98%. About 85% of pediatric blunt renal injuries are considered low grade (grades I-III).

Most pediatric and adult series report successful nonoperative management of even the most complex grade IV and grade V injuries, including shattered but perfused kidneys and complex lacerations with extensive perinephric hematoma and urinary extravasation. Although the AAST grading scale appears to have some predictive value on the need for surgery, indications for surgery are based more on hemodynamic stability of the patient and associated injuries, rather than on grade of renal injury based on imaging criteria. The only absolute indication for surgery is hemodynamic instability with ongoing bleeding and transfusion requirements. Radiographic signs of ongoing renal bleeding include an expanding or uncontained retroperitoneal hematoma or complete avulsion of the main renal artery or vein with extravasation as demonstrated by CT or arteriography. Although not an absolute indication for surgical intervention, active extravasation and pooling of contrast enhanced blood in the arterial phase of the CT scan should be considered a relative indication for surgical intervention depending on the clinical status of the patient, and the clinician should maintain a low threshold for prompt exploration in patients with this CT finding. Recent studies would suggest that about 90% of grade IV injuries with urinary extravasation can be successfully managed nonoperatively in the hemodynamically stable patient.

The caveat to be remembered is that an adjunctive procedure may have to be performed at a later date. If there is no other indication for operation, the patient should be admitted, placed on bed rest and followed for resolution of hematuria.

Note! Serial abdominal CT scans or ultrasonography are helpful in initially evaluating stability and subsequent resolution of hematomas.

Penetrating Injuries:

Penetrating renal injuries are rare in children. Although there is a role for selective nonoperative management, most wounds require surgical exploration.

Selection criteria for nonoperative management include hemodynamic stability, CT for grading of kidney injury and excluding other associated injuries requiring exploration.

However, a high index of suspicion for missed ureteral and other associated injuries must be maintained if a nonoperative pathway is chosen.

Complications

Although most renal injuries in children can be managed nonoperatively, this type of management is not without complications.

These complications are generally seen after injuries in which segments of parenchyma are devascularized or extensive hemorrhage and urinary extravasation have occurred. Obviously, some severe renal injuries require operative intervention consisting of drainage, repair, or nephrectomy.