FENa Calculator

FENa Calculator
mmol/L
μmol/L
mmol/L
μmol/L

Are you tired of calculating your fractional excretion of sodium (FENa) by hand? Well, you’re in luck! Our FENa calculator will do all the work for you, so you can spend your time doing more important things, like figuring out why your cat keeps knocking things off the counter.

FENa Calculation Formula

Here’s the FENa calculation formula in code format:

FENa = (urine Na/serum Na) / (urine Cr/serum Cr)

Categories/Types/Range/Levels of FENa Calculations and Results Interpretation

Category Range Interpretation
Prerenal <1% Dehydration or decreased renal perfusion
Intrinsic Renal >1-2% Acute tubular necrosis, glomerulonephritis, interstitial nephritis
Postrenal >2% Obstruction of urinary tract

Examples of FENa Calculations for Different Individuals

Patient Serum Na Urine Na Serum Cr Urine Cr FENa Calculation
John 140 mEq/L 10 mEq/L 0.8 mg/dL 200 mg/dL 0.71%
Jane 135 mEq/L 50 mEq/L 1.2 mg/dL 100 mg/dL 1.39%

Different Ways to Calculate FENa

Method Advantages Disadvantages Accuracy Level
Spot Urine Noninvasive, easy Variability in urine concentration Moderate
24-Hour Urine Accurate, comprehensive Inconvenient, time-consuming High
Serum and Urine Osmolality More accurate in dehydrated patients Can be affected by other electrolytes High

Evolution of FENa Calculation

Year Evolution
1976 FENa calculation formula introduced
1984 FENa used to differentiate between prerenal and intrinsic renal failure
2004 FENa used to predict fluid responsiveness

Limitations of FENa Calculation Accuracy

  1. Urine Collection Errors: Incomplete urine collection can lead to inaccurate results.
  2. Medications: Diuretics and other medications can interfere with FENa calculation accuracy.
  3. Age and Gender: Age and gender can affect FENa calculation accuracy.

Alternative Methods for Measuring FENa Calculation

Method Pros Cons
FeNa Includes potassium and chloride excretion Requires additional laboratory testing
FeUrea Less affected by diuretics Less sensitive than FENa
FENae Useful in edematous patients Less studied

FAQs on FENa Calculator and FENa Calculations

  1. What is FENa calculation? It is a test to determine whether a patient has prerenal, intrinsic renal, or postrenal failure.
  2. What is a normal FENa level? A normal FENa level is less than 1%.
  3. How is FENa calculated? FENa is calculated using the formula: (urine Na/serum Na) / (urine Cr/serum Cr).
  4. What can affect FENa results? Medications, incomplete urine collection, age, and gender can all affect FENa results.
  5. How is FENa used in clinical practice? FENa is used to differentiate between prerenal and intrinsic renal failure, as well as to predict fluid responsiveness.
  6. What is FeNa? FeNa is an alternative method for measuring sodium excretion in the urine.
  7. Is FENa a reliable test? FENa can be a useful diagnostic tool, but it has limitations and should be used in conjunction with other clinical findings.
  8. What is FENae? FENae is an alternative method for measuring FENa that takes into account the patient’s edema status.
  9. How is FENa used in the emergency department? FENa can help emergency physicians determine the cause of acute kidney injury in critically ill patients.
  10. Can FENa be used in patients with chronic kidney disease? FENa may not be as accurate in patients with chronic kidney disease, and other tests may be more appropriate.

Government/Educational Resources on FENa Calculations

  1. National Kidney Foundation: https://www.kidney.org/atoz/content/fractional-excretion-sodium-fena
  2. American Society of Nephrology: https://www.asn-online.org/education/kidney101/clinical/fena.aspx
  3. MedlinePlus: https://medlineplus.gov/lab-tests/fractional-excretion-of-sodium-fena-test/