Glomerular Filtration Rate Calculator

Calculate estimated Glomerular Filtration Rate (eGFR) using both MDRD and CKD-EPI equations for kidney function assessment.

Understanding Glomerular Filtration Rate (GFR)

Glomerular Filtration Rate (GFR) is the gold standard measure of kidney function, representing the volume of fluid filtered by the kidneys per unit of time. It's essential for diagnosing and staging kidney disease, adjusting medication dosages, and monitoring overall kidney health.

CKD Stages and Clinical Implications

Stage 1: Normal or High (≥90 mL/min/1.73m²)

Normal kidney function but other evidence of kidney disease may be present

Annual monitoring Risk factor modification

Stage 2: Mildly Decreased (60-89 mL/min/1.73m²)

Mild decrease in kidney function with other evidence of kidney disease

Blood pressure control Lifestyle modifications

Stage 3: Moderately Decreased

3a (45-59 mL/min/1.73m²) and 3b (30-44 mL/min/1.73m²)

Regular monitoring Medication review Dietary changes

Stage 4: Severely Decreased (15-29 mL/min/1.73m²)

Severe decrease in kidney function requiring specialist care

Specialist referral Prepare for RRT

Stage 5: Kidney Failure (<15 mL/min/1.73m²)

End-stage kidney disease requiring renal replacement therapy

Dialysis planning Transplant evaluation

Estimation Methods

MDRD Equation

eGFR = 175 × (Scr)^-1.154 × (Age)^-0.203 × [0.742 if female] × [1.212 if Black]
  • Best for GFR <60 mL/min/1.73m²
  • Validated in CKD populations
  • Widely used clinically

CKD-EPI Equation

eGFR = 141 × min(Scr/κ,1)^α × max(Scr/κ,1)^-1.209 × 0.993^Age × [1.018 if female] × [1.159 if Black]
  • More accurate across all GFR ranges
  • Better performance in healthy individuals
  • Preferred for general use
Clinical Pearl: The CKD-EPI equation is generally preferred as it provides more accurate estimates across a wider range of GFR values and has better risk prediction.

Clinical Applications and Monitoring

Diagnostic Applications

  • Initial CKD screening
  • Disease progression monitoring
  • Risk stratification
  • Treatment response assessment

Medication Considerations

  • Drug dosing adjustments
  • Nephrotoxic drug monitoring
  • Contrast media protocols
  • Antibiotic dose modification

Risk Factors to Monitor

  • Hypertension
  • Diabetes mellitus
  • Cardiovascular disease
  • Proteinuria

Factors Affecting GFR Measurement

Physiological Factors

  • Age and gender
  • Muscle mass
  • Pregnancy status
  • Dietary protein intake

Clinical Conditions

  • Acute kidney injury
  • Dehydration status
  • Severe illness
  • Malnutrition
Important Note: GFR estimates should always be interpreted in the clinical context and may require confirmation with more direct measurements in certain situations.

Prevention and Management Strategies

Lifestyle Modifications

  • Dietary sodium restriction
  • Regular physical activity
  • Smoking cessation
  • Weight management

Medical Management

  • Blood pressure control
  • Glycemic control
  • Regular monitoring
  • Specialist referral when needed