What is the difference between eGFR and creatinine clearance?

eGFR (CKD-EPI equation) estimates glomerular filtration rate from serum creatinine and is used for CKD staging. Creatinine clearance (Cockcroft-Gault) estimates renal drug clearance and is preferred for drug dosing adjustments. They use different formulas and may give different results, so it's important to use the right one for the clinical question.

What does FENa tell you?

Fractional excretion of sodium (FENa) helps differentiate prerenal from intrinsic renal causes of acute kidney injury. FENa 2% suggests intrinsic renal disease. FENa can be unreliable in patients on diuretics — use FEUrea instead in those cases.

What is a normal BUN/creatinine ratio?

A normal BUN/creatinine ratio is 10:1 to 20:1. A ratio >20:1 with elevated BUN suggests prerenal azotemia (dehydration, heart failure, GI bleeding). A ratio <10:1 may indicate liver disease, malnutrition, or rhabdomyolysis.

Nephrology Calculators

Renal function tools including eGFR (CKD-EPI), creatinine clearance (Cockcroft-Gault), FENa, BUN/creatinine ratio, free water deficit, urine anion gap, and transtubular potassium gradient. For evaluating kidney function and electrolyte disorders.

This category currently includes 7 tools, including FENa Calculator, BUN/Cr Ratio, and Free Water Deficit.

These resources are built for clinicians, trainees, and medically informed patients who need fast bedside calculations. Use the results as decision support and pair them with full clinical context and local guidelines.

All Nephrology Tools (7)

FENa Calculator

Calculate the Fractional Excretion of Sodium (FENa) to differentiate pre-renal azotemia (FENa <1%) from intrinsic renal disease such as ATN (FENa >2%) in acute kidney injury.

BUN/Cr Ratio

Calculate the BUN/Creatinine ratio to distinguish pre-renal from intrinsic acute kidney injury. Normal ratio 10–20. Ratio >20 suggests pre-renal azotemia; <10 suggests intrinsic renal disease.

Free Water Deficit

Calculate free water deficit for hypernatremia using TBW × (serum Na/140 - 1), with practical 24-hour sodium correction targets and fluid-planning guidance.

Urine Anion Gap

Calculate the urine anion gap to differentiate GI from renal causes of non-anion gap metabolic acidosis. Negative UAG suggests GI bicarbonate loss; positive UAG suggests renal tubular acidosis.

24h Creatinine Clearance

Calculate measured creatinine clearance from a 24-hour urine collection. More accurate than estimated GFR in certain populations.

FEUrea Calculator

Calculate FEUrea to help distinguish pre-renal azotemia from intrinsic AKI, especially when diuretics make FENa unreliable.

Osmolar Gap

Calculate osmolar gap to screen for unmeasured osmoles such as toxic alcohols, ethanol, mannitol, or propylene glycol.

Frequently Asked Questions

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