OpiCalc

Favorites Specialties Drugs Guidelines Most Used

All Specialties

Favorites Specialties Drugs Guidelines Most Used

Faves Specs Drugs Guides Top

ABCD2 Score ACR Criteria Corrected Sodium FENa HEART Score Lights Criteria NEWS2 NRS-2002 Osmolality Gap RCRI (Lee Score)TTKG

OpiCalc

Easy, fast, and private medical tools for clinicians. Always free.

No Login Required

Ready for the Bedside

Resources

About Us Editorial Policy Medical Disclaimer Privacy Policy Terms of Use Cookie Policy

Support

Clinical Notice:OpiCalc is not a substitute for professional clinical judgment. Always verify dosages and guidelines.

OpiCalc © 2018-2026

•

All Rights Reserved

Recent Journal Updates

British J Clinical PharmacologyJun 6, 2026

6‐Mercaptopurine metabolic profiles and clinical outcomes in TPMT and NUDT15 phenotypes during maintenance therapy for Thai paediatric acute lymphoblastic leukaemia

Clinical Context

We think this has broad domain relevance to FENa — Fractional Excretion of Sodium.

WHO NewsJun 5, 2026

Africa CDC and WHO launch joint continental Ebola response plan

Clinical Context

We think this has broad domain relevance to FENa — Fractional Excretion of Sodium.

JAMAJun 2, 2026

Intra-arterial Alteplase After Thrombectomy for Acute Ischemic Stroke

Clinical Context

We think this has broad domain relevance to FENa — Fractional Excretion of Sodium.

FENa

Fractional Excretion of Sodium (FENa): Differentiates between pre-renal causes of AKI and intrinsic renal damage (ATN).

Serum Labs

Sodium (mEq/L)

Creatinine (mg/dL)

Urine Labs

Sodium (mEq/L)

Creatinine (mg/dL)

Guidelines & Evidence

Verified

Last Review: 2026

When to Use

When to Use

Differential diagnosis of Acute Kidney Injury (AKI) in oliguric patients (UOP < 400 mL/day).

Distinguishing prerenal azotemia (hypoperfusion) from intrinsic renal injury, specifically Acute Tubular Necrosis (ATN).

Assessment of the kidney's ability to conserve sodium in the setting of decreased GFR.

Required Parameters

Requires simultaneous (paired) blood and spot urine samples for Sodium and Creatinine.

Last Comprehensive Review: 2026

Related Internal Medicine Tools

Lights Criteria

Corrected Sodium

Internal Medicine Calculators Cardiology Calculators Pulmonary Calculators

Have feedback about this calculator?Let us know.