Acute Kidney Injury

AKI = acute kidney injury is classified further into prerenal, renal, postrenal

Diagnostic criteria

• RIFLE
• AKIN
• doesn’t account for non-oliguric states

Diagnostic approach

• Ultrasound
  • postrenal obstruction
  • prerenal: low volume
• Blood
  • Na, K (and pH can easily be tested with ABG)
  • Creatinine, BUN/Urea
  • Cystatin C
  • specific antibodies in autoimmune AKI
  • …
• Urine
  • Urinalysis
  • Osmolarity
  • Na/Urea, Creatinine
    • low Na indicates prerenal cause
    • Used to calculate fractional excretion of sodium or urea
      • fractional excretion of sodium < 1 %: prerenal, > 2 % renal, cannot be used with diuretics
      • fractional excretion of urea < 35 % prerenal, > 50 % renal, not influenced by diuretics

Therapy

• improve renal perfusion
• stop nephrotoxic medications
  • NSAIDs, aminoglykosides, ACE-inhibitors, AT-receptor blockers, etc.
• treat underlying causes
• furosemide does not improve renal function or revert oliguric kidney failure. Can be used to reduce volume/sodium.

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