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    Patent Pending

    Fractional Excretion of Sodium (FENa)

    Determines if renal failure is due to pre-renal, intrinsic, or post-renal pathology.

    INSTRUCTIONS

    Do not use in patients taking diuretics or with known chronic kidney disease, urinary tract obstruction, or acute glomerular disease. Use FEUrea in patients on diuretics.

    When to Use
    Pearls/Pitfalls
    Why Use

    Patients with oliguria and/or acute kidney injury of unclear etiology.

    • FENa is only clinically validated in patients with oliguric acute kidney injury WITHOUT any of the following: diuretic use, chronic kidney disease (CKD), urinary tract obstruction, or acute glomerular disease.
    • Using urine Na concentration alone is less accurate because it does not account for urine volume and water handling of the kidney by antidiuretic hormone (ADH).
    • Single measurements of serum creatinine are “snapshots” in time and do not reflect true glomerular filtration rate (GFR). The most accurate measurement of GFR is the average of the sum of 24h creatinine clearance and urea clearance.
    • May give an additional data point in patients whose volume status is difficult to assess.
    • Provides a more accurate assessment of kidney function than urine sodium alone (for example, a severely hypovolemic patient may have a relatively high urine sodium, as a fraction of total urine volume, despite having little sodium in the urine).
    mEq/L
    mg/dL
    mEq/L
    mg/dL

    Result:

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    Next Steps
    Evidence
    Creator Insights
    Dr. Carlos Espinel

    About the Creator

    Carlos Espinel, MD, is a cardiologist in Arlington, Virginia and is affiliated with Virginia Hospital Center. In addition to developing the FENa test, his research is the scientific basis for the US Food Labeling Law, which stipulates that food labels must list the exact amount of sodium and other contents. Dr. Espinel is also the creator of ArtMedicine, a medical education model integrating science, humanities and the arts.

    To view Dr. Carlos Espinel's publications, visit PubMed

    Are you Dr. Carlos Espinel? Send us a message to review your photo and bio, and find out how to submit Creator Insights!
    MDCalc loves calculator creators – researchers who, through intelligent and often complex methods, discover tools that describe scientific facts that can then be applied in practice. These are real scientific discoveries about the nature of the human body, which can be invaluable to physicians taking care of patients.
    Content Contributors
    • Devika Nair, MD
    About the Creator
    Dr. Carlos Espinel
    Are you Dr. Carlos Espinel?
    Content Contributors
    • Devika Nair, MD