What is FENa?
FENa stands for Fractional Excretion of Sodium. It is a diagnostic test used to assess the cause of acute kidney injury (AKI) or kidney dysfunction. The FENa test measures the amount of filtered sodium that is excreted in the urine compared to the amount that is reabsorbed by the kidneys. By evaluating the FENa value, healthcare professionals can determine whether the kidneys are functioning properly or if there is a problem.
How is FENa Calculated?
The FENa is calculated using the following formula:
FENa = (urine sodium concentration × plasma creatinine concentration) / (plasma sodium concentration × urine creatinine concentration) × 100
The FENa value is expressed as a percentage. A FENa value less than 1% indicates that the kidneys are conserving sodium and suggests prerenal causes of AKI, such as hypovolemia or renal artery stenosis. On the other hand, a FENa value greater than 2% indicates that the kidneys are not reabsorbing sodium properly and suggests intrinsic renal causes of AKI, such as acute tubular necrosis or glomerulonephritis.
Interpretation of FENa Results
Interpreting the FENa results requires considering the clinical context and the patient’s overall condition. Here are some general guidelines:
- A FENa value less than 1% suggests prerenal causes of AKI.
- A FENa value greater than 2% suggests intrinsic renal causes of AKI.
- However, FENa values between 1% and 2% can be inconclusive and may require further evaluation.
Conclusion
The FENa test is a valuable tool in the diagnosis and management of acute kidney injury. It helps healthcare professionals determine the cause of kidney dysfunction and guide appropriate treatment. Understanding the FENa calculation and interpretation can aid in providing optimal care for patients with kidney disorders.
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