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of the renal lesion. Additionally, hematuria may be absent in up to 50% of
patients with vascular pedicle injuries and in approximately one-third of patients
with penetrating injuries.
Renal injuries have been described using different classification systems based
on the clinical and radiologic assessment of the patient. In 1989, the Organ Injury
Scaling Committee of the American Association for the Surgery of Trauma
developed an injury severity score for classification of renal trauma with minor
modifications made over the years. This classification system is illustrated in
Figure 108.2 and is summarized below:
Grade I injuries include contusions or subcapsular, nonexpanding hematomas
and comprise 80% of all injuries to the kidney.
Grade II injuries include nonexpanding hematomas confined to the perirenal
fascia (Gerota’s) or lacerations less than 1 cm in depth without extension into
the collecting system or urinary extravasation.
Grade III injuries include lacerations extending more than 1 cm into the renal
cortex without collecting system rupture or urinary extravasation.
Grade IV injuries include lacerations extending into the collecting system,
lacerations of the renal pelvis, ureteropelvic junction (UPJ) disruptions, injuries
to the segmental renal arteries or vein, segmental infarctions due to thrombosis,
or active bleeding beyond the perirenal (Gerota’s) fascia.
Grade V injuries include completely shattered kidneys, avulsions of renal hilum
with devascularization of the kidney, or a devascularized kidney with active
bleeding.
Parenchymal contusions and hematomas are the most common renal injuries,
accounting for 60% to 90% of all lesions from blunt trauma. Lacerations account
for up to 10% of renal injuries and may involve disruption of the capsule,
collecting system, or both. Severe injuries, such as shattered kidney or pedicle
avulsions, constitute approximately 3% of renal injuries. Pedicle injuries result
from sheer force of the kidney with subsequent stretching of the renal vessels.

Initial Assessment

Evaluate all injured children thoroughly using a well-established pediatric trauma
protocol. Assessment of the genitourinary system can be undertaken once lifethreatening conditions have been identified and the child has been resuscitated.
Assess for flank and/or abdominal pain and the presence of flank ecchymosis or a
“seat belt sign,” since all of these findings indicate significant trauma and
possible renal injury.


Obtain a urinalysis in all patients with multisystem trauma or suspected
isolated renal injury.

Management/Diagnostic Testing
Hemodynamically stable patients who present with suggestive clinical findings,
gross hematuria, microscopic hematuria of more than 50 RBCs/hpf, major
associated injuries, or a history of significant deceleration injury should undergo
radiographic evaluation. Obtain a contrast-enhanced CT scan with delayed
images. Children who remain unstable despite resuscitative measures should
undergo a one-shot IVP before emergency laparotomy. Children with isolated
microscopic hematuria of less than 50 RBCs/hpf do not require immediate
imaging. These patients may be discharged and can be evaluated on an outpatient
basis with CT, IVP, or ultrasound if hematuria persists. However, in some
pediatric trauma centers, management of these patients involves hospitalization
for observation, followed by nonemergent radiographic evaluation.
The diagnostic performance of imaging modalities as they relate to the
evaluation of renal trauma is reviewed below:
Computed Tomography
Contrast-enhanced CT with additional 10-minute delayed scan is the “gold
standard” imaging modality for staging a stable trauma patient. The delayed scan
or “excretory” phase, occurs after contrast has passed into the renal pelvis and
ureter, allowing better definition and evaluation of these structures. Trauma
patients lacking radiographic signs of renal injury who do not have any

perinephric, periureteral, or pelvic fluid collections do not require delayed
imaging per expert consensus. If any of these subtle findings, especially lowdensity fluid tracking around the kidney and down the ureter, are present on the
initial contrast-enhanced CT, delayed scan is indicated. A UPJ or a ureteral injury
can easily be missed if delayed images are not obtained.
The diagnostic accuracy of CT scan has been reported to be as high as 98% (
Fig. 108.3 ).
The ability of CT to quickly evaluate solid organ and vascular injuries has
significantly improved the management of trauma. Important radiologic findings
that should be noted when reviewing CT for renal trauma include arterial medial
extravasation of contrast, denoting a severe arterial injury; medial hematoma
without arterial extravasation, often secondary to a venous injury; differential
contrast uptake and excretion, which is indicative of arterial injury or thrombosis;
cortical rim sign, often indicative of a main renal artery injury; degree of
parenchymal laceration and involvement of the collecting system; degree of


devitalized tissue; and the size and location of a perinephric hematoma or fluid
collection.


FIGURE 108.2 Classification of renal injuries as proposed by the Organ Injury Scaling
Committee of the American Association for the Surgery of Trauma.