What does a Glomerular Filtration Rate (GFR) of 73 indicate about kidney function and what are the recommended management strategies?

GFR of 73: Normal Kidney Function with Monitoring Recommendations

A glomerular filtration rate (GFR) of 73 mL/min/1.73 m² indicates normal kidney function, falling within stage 2 chronic kidney disease (CKD) classification, and requires routine monitoring but no specific interventions at this time.

Understanding GFR and Kidney Function Classification

• A GFR of 73 mL/min/1.73 m² represents mildly reduced kidney function compared to the normal value in young adults (approximately 120-130 mL/min/1.73 m²), but is still considered within normal range for most adults 1
• According to the Kidney Disease: Improving Global Outcomes (KDIGO) classification system, this value falls into GFR category G2 (60-89 mL/min/1.73 m²), which is classified as mildly decreased GFR 1
• This level of kidney function does not meet the diagnostic threshold for CKD unless other markers of kidney damage are present (such as albuminuria, abnormal urine sediment, or structural abnormalities) 1

Clinical Significance and Risk Assessment

• A GFR of 73 mL/min/1.73 m² alone, without other markers of kidney damage, is not associated with significantly increased risks for adverse outcomes 1
• This level of kidney function is not associated with clinically significant symptoms, as renal dysfunction typically remains asymptomatic until GFR falls below 60 mL/min/1.73 m² 2
• The risk of progression to end-stage renal disease (ESRD) is low with this GFR level, particularly if albuminuria is absent 1, 3

Recommended Monitoring and Management

• For patients with GFR >60 mL/min/1.73 m² without albuminuria, annual monitoring of kidney function is sufficient 1, 4

• Assessment should include:

  • Measurement of serum creatinine and calculation of eGFR 1
  • Urinalysis for albuminuria (albumin-to-creatinine ratio) 1, 4
  • Blood pressure measurement 4

• If albuminuria is present (ACR ≥30 mg/g), more frequent monitoring (twice yearly) is recommended even with preserved GFR 4

Preventive Strategies

• Blood pressure control is essential, with a target of ≤140/90 mmHg for patients without albuminuria 1, 4
• For patients with albuminuria, a lower target of ≤130/80 mmHg may be appropriate 1, 4
• Lifestyle modifications that should be recommended include:
  • Moderate sodium restriction (<2.3g/day) 4
  • Regular physical activity 4
  • Smoking cessation 4
  • Weight management for those with obesity 4

Important Considerations and Caveats

• GFR estimating equations have limitations and may not be equally accurate in all populations 5

• Factors that can affect the accuracy of eGFR calculations include:

  • Extremes of muscle mass or weight 1
  • Non-steady state conditions such as acute illness 1
  • Advanced age (normal age-related decline in GFR) 1

• A single GFR measurement should not be used in isolation for clinical decision-making; trends over time are more informative 5, 3

• A decline in eGFR of 30% or greater over 2 years is associated with increased risk of ESRD and mortality and warrants closer attention 3

When to Consider Nephrology Referral

• With a GFR of 73 mL/min/1.73 m², nephrology referral is generally not necessary unless there are other concerning features 1, 4
• Consider nephrology consultation if:
  • Significant albuminuria (ACR >300 mg/g) is present 4
  • Rapid decline in GFR (>5 mL/min/1.73 m² per year) 4
  • Difficult to control hypertension 4
  • Recurrent urinary tract infections or obstruction 4