Fractional Excretion of Sodium Calculator


Fractional Excretion of Sodium Calculator

Welcome, future nephrology nerds! Ever fantasized about wowing your friends with your deep understanding of renal function calculations? No? Just me? Well, brace yourself for an exciting journey into the thrilling world of the Fractional Excretion of Sodium (FeNa)!


The captivating formula for FeNa is as follows:

FeNa (%) = (urine sodium concentration * plasma creatinine concentration) / (plasma sodium concentration * urine creatinine concentration) * 100


The fascinating world of FeNa is divided into two main categories:

Category FeNa (%)
Prerenal azotemia <1
Intrinsic renal disease >2


Let’s dive into some examples. Meet our imaginary friends John and Jane Doe:

Individual Calculation Result
John Doe (20 * 1.0) / (140 * 100) * 100 0.14 – Prerenal azotemia
Jane Doe (40 * 1.2) / (135 * 150) * 100 2.13 – Intrinsic renal disease


Here are some ways to calculate FeNa, along with their pros and cons:

Method Advantages Disadvantages Accuracy
Direct measurement Most accurate Invasive Very High
Estimation using formula Non-invasive Less accurate Moderate

Evolution of FeNa Calculation

FeNa calculation has come a long way since its inception:

Year Changes
1950s Concept introduced
1980s Formula developed


Like anything else, FeNa calculation has its limitations:

  1. Accuracy: The calculation may not be accurate in all cases.
  2. Time-Dependent: The result can vary depending on the time of measurement.


Here are some alternative methods and their pros and cons:

Method Pros Cons
Urinary osmolality Simple Less accurate
Creatinine clearance More accurate Invasive


Let’s answer some frequently asked questions:

  1. What is FeNa calculation? It’s a method to evaluate kidney function.
  2. Is it accurate? Generally yes, but there can be exceptions.
  3. When was the concept introduced? The concept of FeNa was introduced in the 1950s.
  4. How has the concept evolved? The formula for FeNa calculation was developed in the 1980s.
  5. What are the alternatives to FeNa calculation? Alternatives include urinary osmolality and creatinine clearance.
  6. What are the limitations of FeNa calculation? It may not be accurate in all cases and the result can vary depending on the time of measurement.
  7. What are the categories of FeNa? The categories are prerenal azotemia and intrinsic renal disease.
  8. How is FeNa calculated? FeNa is calculated using the given formula.
  9. What are the advantages and disadvantages of different methods? Direct measurement is the most accurate but invasive, while estimation using formula is non-invasive but less accurate.
  10. Are there any resources for further information? Yes, you can refer to the references section below for more information.


Here are some reliable resources for further research:

  1. National Kidney Foundation: Provides comprehensive information on kidney health and diseases.
  2. American Society of Nephrology: Offers a wealth of resources on nephrology research and education.