What does a Glomerular Filtration Rate (GFR) of 29 indicate?

Interpreting a GFR of 29 ml/min/1.73 m²

A glomerular filtration rate (GFR) of 29 ml/min/1.73 m² indicates severe renal insufficiency, classified as Stage 4 chronic kidney disease, which requires prompt nephrology referral and careful management to prevent progression to kidney failure. 1

Understanding GFR Classification

GFR is the best overall indicator of kidney function and health. A GFR of 29 ml/min/1.73 m² falls into the following classification:

• Stage 4 Chronic Kidney Disease (CKD): GFR 15-29 ml/min/1.73 m² - Severely decreased kidney function 1
• This represents a loss of more than 70% of normal adult kidney function 1
• At this stage, the patient is approaching kidney failure (Stage 5), which is defined as GFR <15 ml/min/1.73 m² or requiring dialysis 1

Clinical Implications of Stage 4 CKD

A GFR of 29 ml/min/1.73 m² has several important clinical implications:

• High risk for progression to end-stage renal disease requiring dialysis or transplantation 1
• Increased risk of cardiovascular disease and mortality 1
• Requires careful medication dosing adjustments for drugs eliminated by the kidneys 1
• May be associated with various complications including electrolyte abnormalities, metabolic acidosis, anemia, and bone disease 1
• Necessitates close monitoring of kidney function every 3-6 months 1

Management Considerations

With a GFR of 29 ml/min/1.73 m², the following management steps are essential:

• Referral to nephrology is strongly recommended at this stage of CKD 1
• Regular monitoring of:
  • Serum creatinine and estimated GFR 1
  • Urinary albumin/creatinine ratio (UACR) 1
  • Electrolytes, particularly potassium 1
  • Hemoglobin, calcium, phosphorus, and parathyroid hormone levels 1
• Strict blood pressure control, preferably with ACE inhibitors or ARBs if proteinuria is present 1
• Careful glycemic control in patients with diabetes 1
• Medication review and dose adjustment for renally excreted drugs 1
• Consideration of renal replacement therapy planning as GFR approaches 15 ml/min/1.73 m² 1
• Protein intake should be approximately 0.8 g/kg/day 1

Important Caveats in GFR Interpretation

When interpreting a GFR of 29 ml/min/1.73 m², consider these important factors:

• Confirm that the low GFR persists for at least 3 months to establish chronic kidney disease 1
• Standard estimated GFR equations may be less accurate in certain populations:
  • Elderly patients with reduced muscle mass 2, 3
  • Patients with extreme body sizes 3
  • Patients with liver disease or malnutrition 3
• In high-consequence medical decisions, direct measurement of GFR may be warranted rather than relying solely on estimated GFR 2, 3
• The estimated GFR value represents a population average and the actual GFR may vary within a range 3

Conclusion for Clinical Practice

A GFR of 29 ml/min/1.73 m² represents severe kidney dysfunction requiring prompt attention. This level of kidney function demands nephrology consultation, careful monitoring of complications, medication adjustments, and preparation for possible future renal replacement therapy. Early intervention at this stage is critical to potentially slow progression to end-stage renal disease and reduce associated cardiovascular morbidity and mortality 1.