Renal Failure Index
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Urine Sodium
unit mEq/L mmol/L
Serum Creatinine
unit mg/dL µmol/L
Urine Creatinine
unit mg/dL µmol/L
R e s u l t s
Renal Failure Index
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Renal Failure Index

Formula:

  • RFI = UNa × SCr/UCr

Details of formula:

  • RFI = Renal Failure Index
  • UNa = Urine Sodium in mEq/L
  • SCr = Serum Creatinine in mg/dL
  • UCr = Urine Creatinine in mg/dL

Interpretation

  • Typical findings prerenal azotemia or glomerulonephritis
    • RFI <1
    • UNa <20 mEq/L
    • FENa <1%
    • UCr/SCr >30
  • Typical findings with ATN (Acute Tubular Necrosis) or post-renal azotemia
    • RFI >1
    • UNa >40 mEq/L
    • FENa >2-3%
    • UCr/SCr <20

References:

  1. Durakovic Z, Durakovic A, Durakovic S. The lack of clinical value of laboratory parameters in predicting outcome in acute renal failure. Ren Fail 1989-90;11(4):213-9.
  2. Miller TR, Anderson RJ, Linas SL, et al. Urinary diagnostic indices in acute renal failure: a prospective study. Ann Intern Med 1978 Jul;89(1):47-50.
  3. Myers BD, Hilberman M, Spencer RJ, et al. Glomerular and tubular function in non-oliguric acute renal failure. Am J Med 1982 Apr;72(4):642-9.
  4. Porush JG. New concepts in acute renal failure. Am Fam Phy 1986 Mar;33(3):109-18.