Renal Failure Index
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Urine Sodium
unit mg/dL 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 x 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:

Durakovic Z, et al. The lack of clinical value of laboratory parameters in predicting outcome in acute renal failure. Ren Fail 1989-90;11(4):213-9.

Miller TR, et al. Urinary diagnostic indices in acute renal failure: a prospective study. Ann Intern Med 1978 Jul;89(1):47-50. Myers BD, et al. Glomerular and tubular function in non-oliguric acute renal failure. Am J Med 1982 Apr;72(4):642-9.

Porush JG. New concepts in acute renal failure. Am Fam Phy 1986 Mar;33(3):109-18.