PUBLIC LIBRARY / CALCULATOR

Fractional excretion of urea (FEUrea)

Measures the percentage of filtered urea excreted. As urea reabsorption depends little on sodium transport, the index remains useful after diuretics.

Calculate with transparency

Check the population, units and version. The result shows the formula or classification; it does not make an automatic treatment decision.

Preparing the form…

Check the method
Enter the data
Check the result

Method · Limits of application

FEUrea/Carvounis 2002: 100×Uurea×PCr/(Purea×UCr); consistent urea/BUN quantities

The 2002 study assessed episodes of acute renal failure, including prerenal causes with and without diuretics and tubular necrosis. Urea fractional excretion was less affected by diuretics in that comparison; this does not make it independent of all interference or confirm the cause from a cutoff alone.

Conditions of use

Check the population, units, inclusion and exclusion criteria, and version in the original source. A result alone does not establish a diagnosis, discharge decision or prescription.

Documented parameters

Urine urea · mg/dL
Serum urea · mg/dL
Urine creatinine · mg/dL
Serum creatinine · mg/dL

3/3 reference cases checked. Numerical tests are not clinical validation.

Sources and documentation

Documented formula

Transcribed from the source or a recorded revision; this is not a clinical recommendation.

FEUrea (%) = (urine urea × serum creatinine) ÷ (serum urea × urine creatinine) × 100.

Urea or BUN yields the same result if the same quantity is used in blood and urine.

References

Carvounis CP, Nisar S, Guro-Razuman S. Significance of the fractional excretion of urea in the differential diagnosis of acute renal failure. Kidney Int, 2002.

Identifier: fracao-de-excrecao-de-ureia

Original clinical content: Brazilian Portuguese.

Method version

FEUrea/Carvounis 2002: 100×Uurea×PCr/(Purea×UCr); consistent urea/BUN quantities

fracao-de-excrecao-de-ureia@native-2026-10-03+0cdc2ef77d94

Source for the active edition

The bibliographic edition identifies the source. By itself, it proves neither full conformity of the formula nor clinical approval.

Synthetic cases checked (3)

Synthetic cases for checking the implementation, with no patient data.

Case 1

reference-001

Inputs

Urine urea: 800 mg/dL
Serum urea: 120 mg/dL
Urine creatinine: 100 mg/dL
Serum creatinine: 2 mg/dL

{
  "uur": 800,
  "pur": 120,
  "ucr": 100,
  "pcr": 2
}

Expected result

{
  "feur": 13.333
}

Actual result

{
  "feur": 13.333333
}

Case 2

reference-002

Inputs

Urine urea: 700 mg/dL
Serum urea: 100 mg/dL
Urine creatinine: 80 mg/dL
Serum creatinine: 4 mg/dL

{
  "uur": 700,
  "pur": 100,
  "ucr": 80,
  "pcr": 4
}

Expected result

{
  "feur": 35
}

Actual result

{
  "feur": 35
}

Case 3

reference-003

Inputs

Urine urea: 500 mg/dL
Serum urea: 100 mg/dL
Urine creatinine: 30 mg/dL
Serum creatinine: 3 mg/dL

{
  "uur": 500,
  "pur": 100,
  "ucr": 30,
  "pcr": 3
}

Expected result

{
  "feur": 50
}

Actual result

{
  "feur": 50
}

Code and reproducibility

This tool’s code on GitHub

Download code and tests

Sources, version and reproduction instructions

The code tests are technical checks. Clinical approval and professional translation review are recorded separately.

Relationship with cancer research

General context — relationship to be defined

A resource for general clinical contexts. This edition does not assign a specific oncological relationship; selecting it for a study requires a justified question, population and purpose.