The kidney is injured in up to 10% of patients who sustain significant abdominal trauma. Overall about 65% of GU injuries involve the kidney. It is the most commonly injured GU organ.
Most renal injuries (85 to 90% of cases) result from blunt trauma, typically due to motor vehicle crashes, falls, or assaults. Most injuries are low grade. The most common accompanying injuries are to the head, CNS, chest, spleen, and liver. Penetrating injuries usually result from gunshot wounds and are usually associated with multiple intra-abdominal injuries, most commonly to the chest, liver, intestine, and spleen.
Renal injuries are classified according to severity into 5 grades (see Figure: Grades of Renal Injury.).
Grades of Renal Injury.
Diagnosis should be suspected in any patient with the following situations:
In such patients, hematuria strongly suggests renal injury; other indicators include the following:
Patients who develop gross hematuria after relatively minor trauma may have a previously undiagnosed congenital renal anomaly.
Laboratory testing should include Hct and urinalysis. When imaging is indicated, contrast-enhanced CT should be used to determine the grade of renal injury and identify accompanying intra-abdominal trauma and complications, including retroperitoneal hemorrhage and urinary extravasation. Patients with blunt trauma and microscopic hematuria usually have minor renal injuries that almost never require surgical repair; thus, CT is usually unnecessary. CT is indicated in blunt trauma in any of the following:
The mechanism involves a fall from a significant height or a high-speed motor vehicle crash
Microscopic hematuria with hypotension (systolic pressure < 90 mm Hg)
Clinical signs potentially suggesting severe renal injury (eg, flank contusion, seat belt marks, lower rib or vertebral transverse process fractures)
For penetrating trauma, CT is indicated for all patients with microscopic or gross hematuria. Angiography may be indicated to assess persistent or delayed bleeding and can be combined with selective arterial embolization.
Pediatric renal injuries are evaluated similarly, except that all children with blunt trauma in whom urinalysis shows > 50 RBCs/high-power field require imaging.
Most blunt renal injuries, including all grade 1 and 2 and most grade 3 and 4 injuries, can be safely treated without active intervention. Active intervention can be surgery or, when necessary, stent placement or angiographic intervention (eg, embolization for certain renovascular injuries). Patients require strict bed rest until gross hematuria has resolved. Intervention is required for patients with the following:
Penetrating trauma usually requires surgical exploration, although observation may be appropriate for patients in whom the renal injury has been accurately staged by CT, BP is stable, and no associated intra-abdominal injuries require surgery.
Most GU injuries involve the kidney, most are due to blunt mechanisms, and most are low grade.
Begin urologic testing with urinalysis and Hct.
Obtain contrast-enhanced CT for suspected moderate or severe injury (eg, mechanism or findings suggesting severe injury, gross hematuria, hypotension).
Consider surgery or angiographic intervention for persistent bleeding, expanding perinephric hematoma, renal pedicle avulsions, and significant renovascular injuries.