Renal Injury

Description

• 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

Etiology

• 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

• 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