Elysia Tools

Browse tools, examples, visual explainers, and topic guides from one clear workspace.

Top Categories

Hubs

Language
ZHESPTRUFRDEEN

Elysia Tools

Navigation

Health

Fractional Excretion of Sodium (FENa)

· Last updated：2026-08-05

This tool is for informational purposes only and does not constitute medical, financial, or legal advice; consult a qualified professional for advice.

Calculate the Fractional Excretion of Sodium (FENa) to differentiate prerenal from intrinsic acute kidney injury: FENa (%) = [U_Na × S_Cr] / [S_Na × U_Cr] × 100. In oliguric AKI, FENa <1% suggests prerenal azotemia (sodium-avid state: volume depletion, heart failure, hepatorenal syndrome), while FENa ≥1% suggests intrinsic injury (typically ATN). FENa >4% is sometimes cited as supportive of post-obstructive pathology. Caveats: unreliable on diuretics (use FEUrea <35%), contrast/sepsis ATN can present with low FENa, chronic CKD and glucosuria elevate FENa independently. Derived from Espinel CH, JAMA 1976. Most useful in oliguric AKI; interpret with full clinical context. Not medical advice.

Execution

Run this tool

Fill in the form, run the tool, and review the result in one place.

Samples

Examples that match this tool

Related

Continue with connected tools and hubs

Written by the Elysia Tools team

Tool usage guide

Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Category
Health
Input types
number
Output type
json
Sample coverage
4
API ready
Yes

Overview

The Fractional Excretion of Sodium (FENa) calculator estimates the percentage of filtered sodium excreted in urine using urine sodium, serum creatinine, serum sodium, and urine creatinine. In oliguric acute kidney injury, the result can help distinguish prerenal azotemia from intrinsic renal injury, but it must be interpreted with the full clinical context.

When to use

  • Assess oliguric acute kidney injury when prerenal azotemia and intrinsic renal injury are being considered.
  • Review urine and serum laboratory values using the standard FENa formula.
  • Support clinical interpretation alongside volume status, medications, comorbidities, and other kidney findings.

How it works

  1. 1Enter urine sodium in mmol/L, serum creatinine in mg/dL, serum sodium in mmol/L, and urine creatinine in mg/dL.
  2. 2The calculator applies FENa (%) = (urine sodium × serum creatinine) ÷ (serum sodium × urine creatinine) × 100.
  3. 3Choose the number of decimal places for the displayed result, from 0 to 8.
  4. 4The output reports the FENa percentage, category, and a related interpretation such as prerenal azotemia or intrinsic renal injury.

Use cases

  • Nephrology review of urine and serum measurements in oliguric acute kidney injury.
  • Clinical education on the relationship between sodium handling and acute kidney injury categories.
  • Quick documentation or verification of FENa calculations using standardized laboratory inputs.

Examples

1. Low FENa consistent with prerenal azotemia

Clinician reviewing an oliguric AKI case

Background

The patient has urine sodium of 20 mmol/L, serum creatinine of 1.5 mg/dL, serum sodium of 140 mmol/L, and urine creatinine of 120 mg/dL.

Problem

Calculate FENa and review whether the result is consistent with a sodium-avid state.

How to use

Enter 20 for urine sodium, 1.5 for serum creatinine, 140 for serum sodium, and 120 for urine creatinine. Set decimal places to 4.

urineSodium=20; serumCreatinine=1.5; serumSodium=140; urineCreatinine=120; decimalPlaces=4

Outcome

The calculator returns FENa = 0.1786%, below 1%, consistent with prerenal azotemia in the appropriate clinical context.

2. FENa in the intrinsic injury range

Medical trainee studying AKI classification

Background

The laboratory values are urine sodium 60 mmol/L, serum creatinine 2.0 mg/dL, serum sodium 135 mmol/L, and urine creatinine 60 mg/dL.

Problem

Use the standard formula to calculate FENa and identify the reported category.

How to use

FAQ

What does FENa measure?

FENa estimates the percentage of filtered sodium that is excreted in the urine.

What does a FENa below 1% suggest?

In oliguric acute kidney injury, a value below 1% is consistent with prerenal azotemia or another sodium-avid state.

What does a FENa of 1% or higher suggest?

A value of at least 1% is consistent with intrinsic renal injury, typically acute tubular necrosis.

Can diuretics affect FENa interpretation?

Yes. Diuretics can make FENa unreliable; FEUrea may be considered instead, with a value below 35% often used in this context.

Is this calculator medical advice?

No. FENa should be interpreted by a qualified clinician with the complete clinical picture.

Hub

Renal Function, Dialysis, and Dose-Model Checks

Compare kidney-function formulas, dialysis adequacy metrics, and renal medication math in an educational workflow that avoids patient-specific dosing or diagnosis.

Home
Tools3201
Samples593
Visualizations465
Viewers103
Hubs233
Tags333
Images, Audio & Video657

Image, audio, and video processing, conversion, and optimization tools

Math, Date & Finance644

Calculators, numerics, date logic, statistics, and finance tools

Design & Color297

Color, layout, graphics, visual styling, and design helper tools

Text & Writing209

Writing, cleanup, formatting, extraction, and text analysis tools

Developer & Web193

Developer utilities, networking, web debugging, and automation helpers

Conversion & Encoding175

Format, file, archive, unit, and encoding conversion tools

FLAC/WAV Source Screening and Evidence Handoff
Self-Hosted Giveaway Widget Review and Embed Handoff
Stripe Promo Code Batch Review and Import Preflight
Batch Photo Culling Review and Editing Shortlist Handoff
UI Screenshot Structure Review and Development Handoff

© 2026 Elysia Tools. All rights reserved.

DocsPricingAboutTerms of ServicePrivacy PolicyCookiesContact
Python

Web Image Processing Python Samples

Web Python image processing examples using PIL/Pillow including reading, saving, resizing, and format conversion

Java

Android Image Processing Java Samples

Android Java image processing examples including reading/saving images, scaling, and format conversion

Kotlin

Android Image Processing Kotlin Samples

Android Kotlin image processing examples including reading/saving images, scaling, and format conversion

Media

SVG Samples

Scalable Vector Graphics (SVG) samples demonstrating various SVG features and techniques

Media

Adaptive 12-Point Hidden Watermark

Add a subtle text watermark to one image or every supported image in a ZIP, at all, random, or chosen perimeter positions with automatic dark/light local contrast.

Health

Cardiac Output by Thermodilution (Stewart-Hamilton)

Compute CO = V × (T_b − T_i) × 60 × 1.08 / A from a thermodilution curve, with optional cardiac index from BSA (normal 2.5–4.0 L/min/m²). Not medical advice.

Health

IV Drip Rate Calculator (Gravity)

Calculate the gravity (manual) IV drip rate in drops per minute: gtt/min = Volume × Drop factor / Time. Drop factor selectable (macro 10/15/20 or micro 60 gtt/mL). Time may be hours+minutes or minutes; rounded to whole drops with drift warning. Vasoactive/cardiotonic drugs and pediatric infusions must ALWAYS use a pump. Derived from Philips 2007, Macklin 2011, MDCalc, and ISMP. Not medical advice.

Math & Numbers

Minimum Spanning Tree (Kruskal / Prim)

MST with both textbook algorithms: Kruskal's sorted accept/cycle-reject log and Prim's component growth, cross-checked to agree on the total weight; disconnected graphs rejected.

Enter the four laboratory values and select 4 decimal places for the result.

urineSodium=60; serumCreatinine=2.0; serumSodium=135; urineCreatinine=60; decimalPlaces=4

Outcome

The calculator returns FENa = 1.4815%, in the 1–4% category and consistent with intrinsic renal injury, typically acute tubular necrosis.