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FeNa & TTKG

Fractional Excretion of Sodium & Transtubular Potassium Excretion

Calculate FENa:

Sodium:

Serum (PNa): mmol/L
Urinary (UNa): mmol/L

Creatinine:

Serum (PCr): mg/dl
Urinary (UCr): mg/dl
Fractional Excretion of Sodium (FENa) = %
Renal Failure Index (RFI) = %

Calculate TTKG:

Potassium:

Serum (PK): mmol/L
Urinary (UK): mmol/L

Osmolality:

Serum (POsm): mOsm/L
Urinary (UOsm): mOsm/L
Transtubular Potassium Gradient (TTKG) = %

Fractional Excretion of Sodium (FENa) = (UNa x PCr) / (PNa x UCr) x 100

Renal Failure Index (RFI) = (UNa x PCr) / UCr

Transtubular Potassium Gradient (TTKG) = (UK x Posm) / (PK x Uosm)

Interpretation of the Urinary Indices


  Prerenal ATN Postrenal
UNa (mmol/L) < 20 > 40 > 40
FENa < 1% > 1% > 4%
RFI < 1% > 1% > 1%

DISCLAIMER

DISCLAIMER: All calculations must be confirmed before use. The authors make no claims of the accuracy of the information contained herein; and these suggested doses are not a substitute for clinical judgement. Neither ValueMD nor any other party involved in the preparation or publication of this site shall be liable for any special, consequential, or exemplary damages resulting in whole or part from any user's use of or reliance upon this material.


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