Renal Injury



  • Kidneys are located in the retroperitoneal space and are surrounded by adipose tissue and loose areolar connective tissue:
    • Protected by the lower ribs, back musculature, and perinephric fat
  • Kidneys lie along the lower 2 thoracic vertebrae and first 4 lumbar vertebrae
  • Left kidney is positioned slightly higher than the right due to the presence of the liver
  • Kidneys are not fixed:
    • Shift with the diaphragm and are supported by the renal arteries, veins, and adipose tissue to the renal (Gerota) fascia


  • Most common of all urologic injuries
  • Occurs in ∼8–10% of all abdominal trauma
  • Blunt renal trauma accounts for 80–85% of all renal injuries and is 5 times more common than penetrating injury:
    • Mechanisms include motor vehicle accidents, falls, domestic violence, and contact sports
    • Pathophysiology includes rapid deceleration and displacement mechanisms
    • ∼20% of cases are associated with intraperitoneal injury
  • Mechanisms responsible for significant renal injury almost never affect the kidney alone:
    • Most often disrupt and injure other vital organs that can be responsible for patient mortality
  • Renal injuries are graded by type and severity of injury (Association for the Surgery of Trauma [AAST] criteria)
    • Grade I:
      • Contusion: Microscopic or gross hematuria, urologic studies normal
      • Hematoma: Subcapsular, nonexpanding without parenchymal laceration
    • Grade II:
      • Hematoma: Nonexpanding, perirenal hematoma confined to retroperitoneum
      • Laceration: <1 cm parenchymal depth of renal cortex without urinary extravasation
    • Grade III:
      • Laceration: >1 cm parenchymal depth of renal cortex without collecting system rupture or urinary extravasation
    • Grade IV:
      • Laceration: Parenchymal laceration extending through renal cortex, medulla, and collecting system
      • Vascular: Main renal artery or vein injury with contained hemorrhage
    • Grade V:
      • Laceration: Completely shattered kidney
      • Vascular: Avulsion of renal hilum, devascularizing the kidney

Pediatric Considerations
  • The kidney is the organ most commonly damaged by blunt abdominal trauma:
    • Bicycle accidents are an important mechanism of injury
  • Contributing factors:
    • Relatively larger size of kidneys compared with adults
    • Tenth and eleventh ribs are not completely ossified until the third decade of life
  • Significant abdominal injury occurs in about 5% of nonaccidental trauma cases but is the second most common cause of death after head injury
  • Children may not manifest hypotension with renal injury as often as adults

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