Renal Failure (Acute Kidney Injury)

Renal Failure (Acute Kidney Injury) is a topic covered in the 5-Minute Emergency Consult.

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  • The disorder is now known as acute kidney injury (AKI); the term renal failure is outdated.
  • Changes in glomerular filtration rate (GFR) and urine output (UO) encompassing a spectrum ranging from normal physiologic response to end-stage renal disease (ESRD) and measured by accumulation of nitrogenous by-products.
  • Defined by the RIFLE criteria:
    • 3 stages of renal injury:
      • Risk: Increased creatinine (Cr) ×1.5 or GFR decrease >25%, UO <0.5 mL/kg/h × >6 h
      • Injury: Increased Cr ×2 or GFR decrease >50%, UO <0.5 mL/kg/h × >12 h
      • Failure: Increased Cr ×3 or GFR decrease >75% or Cr ≥4 mg/dL (acute rise of ≥0.5 mg/dL), UO <0.3 mL/kg/h × 24 h or anuria × 12 h
    • 2 stages of outcome:
      • Loss: Loss of renal function >4 wk
      • ESRD: Loss of renal function >3 mo
  • The most severe marker defines stage.
  • AKI based upon changes within last 48h; however, must often base on most recent data.
  • Higher RIFLE stages correlate with higher 1 and 6 mo mortality rates for hospitalized patients.


  • Prerenal AKI:
    • Caused by renal hypoperfusion
    • Renal tissue remains normal unless severe/prolonged hypoperfusion.
  • Intrarenal AKI:
    • Caused by diseases of the renal parenchyma
  • Iatrogenic AKI causes include:
    • Aminoglycoside antibiotics
    • Radiocontrast material administration
    • NSAIDs
    • ACE inhibitors
    • Angiotensin receptor blockers
  • Postrenal AKI:
    • Due to urinary tract obstruction (e.g., prostatic hypertrophy, prostatitis)

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