FENA

• • FeNa = (urine Na/plasma Na)/(urine creatinine/plasma creatinine)*
  • FeNa <1 % = prerenal ARF
  • FeNa >1% = ATN

• *FeNa best interpreted in oliguria

• Exceptions (intrinsic renal failure with FeNa <1%)

• • Urinary tract obstruction
  • Acute glomerulonephritis
  • Hepatorenal syndrome
  • Radiologic contrast–induced ATN
  • Myoglobinuric and hemoglobinuric ARF
  • Renal allograft rejection
  • Drug-related alterations in renal hemodynamics (eg, captopril, NSAIDs)