Uric acid feua Assessment Tool — Free nephrology Risk Score Calculator

How it Works

Fractional Excretion of Uric Acid (FEUA)

FEUA (%) = [(Urine Uric Acid × Serum Cr) / (Serum Uric Acid × Urine Cr)] × 100

Renal Handling Thresholds

Normal FEUA	7% – 12%
Underexcretion	< 6% (Renal cause)
Overproduction	> 12% (Metabolic/Dietary cause)

Physiological Process

Urate undergoes a complex "four-component" process in the nephron: 1) Glomerular filtration, 2) Near-complete proximal reabsorption, 3) Tubular secretion, and 4) Post-secretory reabsorption. Roughly 90% of filtered urate is reabsorbed.

Clinical Pearls

Underexcretion vs. Overproduction

90% of gout patients are "underexcretors" at the renal level.

Overproduction (FEUA > 12%) suggests myeloproliferative disorders, tumor lysis, or high purine intake.

A 24-hour urine collection showing > 800 mg (men) or > 750 mg (women) of uric acid on a normal diet confirms overproduction.

Drug Interactions

Low-dose Aspirin inhibits urate secretion, increasing serum levels.

Diuretics (Thiazides/Loops) increase urate reabsorption via volume depletion.

Losartan and SGLT2 inhibitors are uricosuric (increase FEUA) and can lower serum levels.

The "Urate Gap"

In Acute Kidney Injury (AKI) due to Tumor Lysis Syndrome, the Urine Uric Acid-to-Creatinine ratio is typically > 1.0, helping distinguish it from other causes of AKI.

Next Steps

Management Decisions

01

If Underexcretor: Prioritize xanthine oxidase inhibitors (Allopurinol/Febuxostat). Consider uricosurics (Probenecid) if renal function is preserved (eGFR > 30).

02

If Overproducer: Screen for malignancy or enzymatic defects; restrict high-purine foods and fructose.

03

Stone Prevention: For uric acid stones, prioritize urinary alkalinization (Target pH 6.2 – 6.8) using Potassium Citrate.

04

Acute Gout: Do NOT start Allopurinol during an acute flare; wait 2 weeks after resolution.

Related Tools

CKD-EPI eGFR Calculator

Fractional Excretion of Sodium (FENa)

24-Hour Urine Interpretation

The Evidence

Core Guidelines

2020 American College of Rheumatology Guideline for the Management of Gout.

FitzGerald JD et al. • Arthritis Care & Research. 2020;Provides the standard targets for urate-lowering therapy and the role of renal assessment.

Renal Handling Study

Regulation of uric acid excretion by the kidney.

Lipkowitz MS. • Current Rheumatology Reports. 2012;Review of the URAT1 and ABCG2 transporters responsible for the FEUA thresholds used in clinical calculators.

Origins & History

Evolution of Theory

The concept of fractional excretion was adapted from sodium physiology in the 1970s. The specific application to uric acid allowed nephrologists to pinpoint the tubular defects (specifically in the URAT1 transporter) that lead to familial hyperuricemia and gout.

Uric Acid & FEUA

When to Use

When to Use

Target Population

How it Works

Fractional Excretion of Uric Acid (FEUA)

Renal Handling Thresholds

Physiological Process

Clinical Pearls

Underexcretion vs. Overproduction

Drug Interactions

The "Urate Gap"

Next Steps

Management Decisions

Related Tools

The Evidence

Core Guidelines

2020 American College of Rheumatology Guideline for the Management of Gout.

Renal Handling Study

Regulation of uric acid excretion by the kidney.

Origins & History

Evolution of Theory

In Recent Clinical News

Uric Acid & FEUA

When to Use

When to Use

Target Population

How it Works

Fractional Excretion of Uric Acid (FEUA)

Renal Handling Thresholds

Physiological Process

Clinical Pearls

Underexcretion vs. Overproduction

Drug Interactions

The "Urate Gap"

Next Steps

Management Decisions

Related Tools

The Evidence

Core Guidelines

2020 American College of Rheumatology Guideline for the Management of Gout.

Renal Handling Study

Regulation of uric acid excretion by the kidney.

Origins & History

Evolution of Theory

In Recent Clinical News