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Acute Tubular Necrosis

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Topic updated on 09/26/16 1:11pm

Introduction
  • Most common cause of AKI
  • Intrinsic "renal" category
  • Caused by ischemic kidney, leading to tubule necrosis
  • Causes 
    • sepsis
    • trauma
    • hypotension
    • hemorrhage
    • crush injury or rhabdomyolysis (myoblobineria)
    • direct toxins (heavy metal)
      • radiograph contrast agents
    • transplant
    • drugs
      • aminoglycosides
  • Three phases of injury
    • prodromal
    • oliguric
    • postoliguric
Symtoms
  • Symptoms
    • uremia
    • generalized edema
    • seizures
    • easy bruising or bleeding
    • vomiting blood
    • bloody stools or urine 
Evaluation
  • Urinalysis
    • urine osmolarity = 300-350 mosm/L (never < 300)
    • urine sodium = > 20 mEq/L
    • fractional excretion of sodium = > 2%
  • Microscopic urine analysis shows
    • muddy brown granular casts
  • Ultrasound shows debris in the collecting system
  • Gross pathology shows pale swollen kidney and cortex and congested medullary parenchyma
  • Histopathology shows
    • dilated convoluted tubules and their necrotic epithelial walls that shed into the lumen
    • glomeruli are relatively intact
Differential

Disease
Microscopic Urine Analysis
End Stage Renal Failure Waxy casts
ATN muddy brown granular casts
Pyelonephritis White Blood Cell (WBC) Casts
Glomerulonephritis Red Blood Cell Casts (pathognomonic)
Nephrotic Syndrome Double-refractile fat bodies
Atheroembolic disease Urinary eosinophils
Allergic nephriti Urinary eosinophils

Treatment
  • Resolution of precipitating cause
  • IV fluids to maintain urinary output
  • Monitor and correct electrolytes
  • Diuresis as needed to prevent fluid overload


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