Kymora Scotland, MD, PhD
T. Ernesto Figueroa, MD, FAAP, FACS
BASICS
DESCRIPTION
• Traumatic injury overall is the leading cause of childhood death in the United States.
• Pediatric renal trauma is subdivided into blunt and penetrating mechanisms of injury.
• The pediatric kidney is believed to be more susceptible to trauma vs. the adult kidney.
• Over the past 2 decades, the management of pediatric renal trauma has shifted from operative intervention to conservative management.
EPIDEMIOLOGY
Incidence
• 10–20% of all abdominal blunt trauma involves a renal injury.
• 90% of GU injuries are from blunt trauma.
• Nearly 90% of patients with GU injuries have coexisting injuries to the thorax, spine, pelvis, or intra-abdominal organs.
Prevalence
N/A
RISK FACTORS
• Pre-existing GU abnormalities (ie, ureteropelvic junction obstruction horseshoe kidney vs. pelvic kidney):
– 3–5-fold more common in pediatric patients undergoing CT for trauma
– Classically presents with a history of hematuria disproportionate to the severity of trauma
• Decrease in physical renal protective mechanisms:
– More pliable thoracic cage and weaker abdominal muscles
– Less renal fat
– Position of the kidney within the abdomen
Genetics
Disorders that lead to an increase in GU anomalies have a greater risk for traumatic injury
PATHOPHYSIOLOGY
• Tissue or organ injury from external source of energy
• Grading system:
– Grade I: Subcapsular hematoma, microscopic or gross hematuria, normal radiographic studies
– Grade II: Nonexpanding perirenal hematoma or cortical laceration <1 cm deep
– Grade III: Laceration >1 cm in parenchyma without collecting system rupture or urine extravasation
– Grade IV: Parenchymal laceration through renal cortex, medulla, collecting system; contained main renal artery or vein hemorrhage
– Grade V (shattered kidney): Renal pedicle avulsion, multiple parenchymal lacerations, major injury to the renal vessels, urinary extravasation
ASSOCIATED CONDITIONS
Injury to other organ systems
GENERAL PREVENTION
Measures that decrease traumatic injury in general, such as seat belts, air bags
DIAGNOSIS
HISTORY
• Mechanism of injury: Degree of actual traumatic injury may not correlate with the mechanism
– Blunt: Falls, automobile collision, sporting injuries, etc.
– Penetrating: Gunshot wound, stabbing, etc.
• Vital signs in the field:
– Hypotension: Children will often have a normal BP despite a significant blood loss.
• Hematuria: Unlike adults, an unreliable indicator of underlying renal injury in children:
– Up to 70% of children with grade II or higher renal injury may have neither gross nor microscopic hematuria.
• Medical history: Any acute or chronic medical conditions and any previous GU abnormality
• Surgical history: Previous urologic procedure for reflux, stone, hypospadias, etc.
• Iodine or latex allergy
• Loss of consciousness
PHYSICAL EXAM
• Vital signs and ABCD of resuscitation to stabilize patient
• BP is often normal in severely hypovolemic children
• Exposure: Observe for obvious signs of abdominal/flank/thoracic trauma, abdominal/flank tenderness, flank ecchymosis, gross hematuria, pelvic instability
• DRE: Observe for perineal ecchymosis
• If blood at the urethral meatus, do not insert catheter
ALERT
Degree of hematuria does not correlate with degree of injury.
DIAGNOSTIC TESTS & INTERPRETATION
Lab
• CBC, basic metabolic profile, coagulation profile
• Urinalysis
– Unreliable in determining the extent of GU trauma
– Up to 70% of children with grade II renal trauma will have neither gross nor microscopic hematuria.
ALERT
The patient’s hemodynamic status determines when and what type of imaging modality is indicated.
Imaging
• Indications for radiographic imaging: All penetrating abdominal trauma or blunt trauma victims with 1 of the following criteria (1):
– Significant deceleration or high-velocity injury: MVA, fall from >15 ft
– Trauma resulting in fracture of the thoracic cage, spine, pelvis, or femur, or bruising of the torso/perineum
– Acute peritonitis
– Gross hematuria
– Microscopic hematuria (>50 RBC/HPF) associated with shock (SBP <90 mm Hg)
– Delayed hemorrhage following renal trauma
• CT:
– Currently the most commonly used imaging modality in these patients
– Triphasic abdominal and pelvic CT (ideally): Clinically stable patients; most sensitive method for diagnosing and classifying GU trauma, precontrast phase, nephrogram phase after injection of contrast, and delayed images at 15 min. The downside of this is radiation exposure.
– Single-phase CT: Clinically labile patients; allows for determination of renal perfusion and major renal fractures. This can be followed by a KUB to assess renal integrity.
– Delayed CT: Obtained postoperatively after patient is stabilized or after patient is resuscitated in the ICU for full trauma evaluation; used to assess grade 3–5 renal injuries 2–3 days posttrauma to assess for baseline hematoma or urinoma
• Focused assessment with sonography for trauma (FAST):
– Often combined with serial physical exams as a screening modality after blunt trauma
– Sensitivity ranges from 70–85% and specificity ranges from 93–100%; operator dependent
– Option in areas with limited radiologic resources
• Arteriography:
– Used for diagnosis of arteriovenous fistula in the setting of delayed hemorrhage following renal trauma
• Retrograde pyelography:
– Rule out presence of partial/total ureteral disruption
– Management of symptomatic urinoma with placement of ureteral stent
• Single-shot IVP:
– Increasingly limited role
– Done after patient is hemodynamically stable following trauma-exploratory laparotomy; allows for visualization of functioning contralateral kidney when considering unilateral nephrectomy
• DMSA scan:
– Allows for quantification of renal function for grade 3–5 injuries; obtain at least 1 wk after traumatic injury, also indicated
• Follow-up imaging:
– Triphasic CT is indicated for patients with persistent fever, worsening flank pain, or gross hematuria >72 hr after injury
Diagnostic Procedures/Surgery
N/A
Pathologic Findings
N/A
DIFFERENTIAL DIAGNOSIS
Injury to other major abdominal viscera in the setting of acute trauma
TREATMENT
GENERAL MEASURES
• The major challenge facing the urologist in evaluating pediatric renal trauma is in determining when to surgically intervene.
• The decision to intervene operatively is based on 3 clinical indicators: Hemodynamic stability, accurate radiographic staging, presence of associated organ injuries (2).
• In general:
– Irrespective of the mechanism of injury and provided there are no absolute indications for abdominal exploration then all renal trauma can be observed.
– Renal exploration and renorrhaphy for grade III or higher renal injuries should be carried out if laparotomy is necessary for coexisting intra-abdominal injuries.
– Renal exploration may be excluded in patients with concurrent intra-abdominal injuries if the urinary tract is separated from the enteric tract by omentum or other tissue, and adequate drains are left in place.
• Renal injury classification: Based on American Association for the Surgery of Trauma (AAST) renal injury grading system (see “Renal Trauma, Adult”)
MEDICATION
First Line
• Basic fluid and transfusion management
• Broad-spectrum antibiotics for penetrating injury and blunt trauma with urinary extravasation or large retroperitoneal hematoma
Second Line
N/A
SURGERY/OTHER PROCEDURES
• Absolute indications for renal exploration:
– Hemodynamic instability from a renal source
– Expanding or pulsatile retroperitoneal hematoma
– Inability to stop persistent or delayed hemorrhage via selective vascular embolization
• Relative indications for renal exploration:
– Patients with vascular instability resulting in an inability to obtain adequate preoperative radiographic studies
– Retroperitoneal hematoma found at the time of surgical exploration
– Known grade III or higher renal injury during concomitant abdominal exploration: Either perform renal exploration with renorrhaphy or separation of GI from GU tract and drain placement
• Renal salvage via renorrhaphy or partial nephrectomy requires complete exposure of the injured kidney, debridement of nonviable tissue, repair of the collecting system, and ligation of all bleeding vessels.
– Renal pelvic or ureteral injuries should be closed watertight; if not, then ureteral stents or nephrostomy tube may be necessary.
– Nephrectomy should be considered in the setting of irreparable grade IV–V injures and in cases where nephrectomy would help control bleeding in the coagulopathic or hypothermic patient.
– Renal vascular injuries: The kidney is an end organ; segmental renal vessel repair should not be attempted, main renal artery reconstruction should only be considered if patients are hemodynamically stable and have either a solitary kidney or bilateral renal injuries.
– Endoscopic stent placement and/or percutaneous placement of perirenal drain or nephrostomy tube in cases of expanding urinoma
ADDITIONAL TREATMENT
Radiation Therapy
N/A
Additional Therapies
• Nonoperative management (3)
– Initially only for if hemodynamically stable
– Admission to ICU for monitoring is warranted:
Bed rest, monitor urine output, serial abdominal exams, serial hemoglobin/HCT, resuscitate and transfuse as necessary
• Ideal candidate will have grade I–II injury
• Patients with isolated grade III, IV, and V renal injuries are candidates for nonoperative treatment:
– Conservative management of isolated grade III–IV renal injuries will prevent 95% of patients from requiring operative intervention
– Angiographic, endoscopic, or percutaneous intervention will be required in up to 55% of patients
Complementary & Alternative Therapies
N/A
ONGOING CARE
PROGNOSIS
• Based on the overall renal function following the traumatic injury
• Renal vascular HTN
– Usually develops within 36 mo after injury
– DMSA scan is indicated to determine differential renal function
– CT angiogram may be necessary to rule out arteriovenous fistula as the source of HTN
• End-stage renal disease
– Bilateral renal injury
– May require peritoneal or hemodialysis
FOLLOW-UP
Patient Monitoring
• Repeat CT of the kidney 2–3 days after trauma for grade III or higher renal injuries.
– Have low threshold for repeat CT if patient has decreasing hemoglobin/HCT despite blood transfusion or if child is hemodynamically unstable.
• Ambulation should resume when gross hematuria resolves.
– Strenuous physical activity should be avoided for 6 wk.
REFERENCES
1. Buckley JC, McAninch JW. The diagnosis, management, and outcomes of pediatric renal injuries. Urol Clin N Am. 2006;33:33–40.
2. Husmann D. Pediatric genitourinary trauma. In: Wein AJ, Kavoussi LR, Novick AC, et al, eds. Campbell-Walsh Urology. 9th ed. Philadelphia, PA: Saunders Elsevier; 2007:3929–3945.
3. Jacobs MA, Hotaling JM, Mueller BA, et al. Conservative management vs early surgery for high grade pediatric renal trauma–do nephrectomy rates differ? J Urol. 2012;187(5):1817–1822.
ADDITIONAL READING
• Kawashima A, Sandler CM, Corl FM, et al. Imaging of renal trauma: A comprehensive review. Radiographics. 2001;21:557–574.
See Also (Topic, Algorithm, Media)
• Bladder Trauma
• Renal Trauma, Adult
• Renal Trauma, Adult Algorithm 
• Renal Trauma, Adult Images 
• Retroperitoneal Hematoma
• Ureter, Trauma
• Wunderlich Syndrome
CODES
ICD9
• 866.00 Injury to kidney without mention of open wound into cavity, unspecified injury
• 866.01 Injury to kidney without mention of open wound into cavity, hematoma without rupture of capsule
• 866.02 Injury to kidney without mention of open wound into cavity, laceration
ICD10
• S37.009A Unspecified injury of unspecified kidney, initial encounter
• S37.019A Minor contusion of unspecified kidney, initial encounter
• S37.039A Laceration of unsp kidney, unspecified degree, init encntr
CLINICAL/SURGICAL PEARLS
Hemodynamically stable patients can be managed conservatively.