From the Guidelines
A GFR of 40 mL/min/1.73m² in a 70-year-old indicates moderate chronic kidney disease (CKD stage 3b), necessitating regular monitoring and management to prevent progression and complications. This classification is based on the guidelines from the National Kidney Foundation, which define chronic kidney disease as a GFR less than 60 mL/min per 1.73 m2, regardless of age 1. The prevalence of complications of chronic kidney disease increases with decreasing GFR, and a GFR of 40 represents a significant loss of kidney function.
Key aspects of management include:
- Controlling blood pressure to a target of less than 130/80 mmHg, typically using ACE inhibitors or ARBs if appropriate, as these have been shown to slow the progression of kidney disease 1.
- Adjusting medication dosages, as many drugs are cleared by the kidneys and decreased GFR in the elderly requires adjustment in drug dosages 1.
- Avoiding nephrotoxic medications like NSAIDs or using them with extreme caution.
- Regular laboratory monitoring every 3-6 months to track kidney function, electrolytes, and metabolic parameters.
- Implementing lifestyle modifications, including moderate protein intake (0.8 g/kg/day), adequate hydration, sodium restriction to less than 2 grams daily, and management of other conditions like diabetes (target HbA1c around 7%).
Given the age-related decline in GFR, a GFR of 40 in a 70-year-old, although indicative of impaired renal function, is not unusual but still warrants careful management to prevent further decline and complications. Referral to a nephrologist should be considered, especially if there is a rapid decline in function, significant proteinuria, or difficulty managing complications.
From the Research
Significance of a Glomerular Filtration Rate (GFR) of 40
- A GFR of 40 mL/min/1.73 m2 indicates impaired renal function, which is a significant concern in a 70-year-old individual 2, 3.
- According to the studies, chronic kidney disease (CKD) is defined as a persistent abnormality in kidney structure or function, including a GFR <60 mL/min/1.73 m2 or albuminuria ≥30 mg per 24 hours, for more than 3 months 2, 3.
- The diagnosis of CKD should include assessing the GFR, albuminuria, and the cause of the disease, as well as documentation of the trajectory and prognosis 4.
- A GFR of 40 mL/min/1.73 m2 falls into stage 3 CKD, which requires monitoring and management to prevent progression to end-stage kidney disease and cardiovascular disease 2, 3.
Management and Monitoring
- Optimal management of CKD includes cardiovascular risk reduction, treatment of albuminuria, avoidance of potential nephrotoxins, and adjustments to drug dosing 2, 3.
- Patients with CKD require monitoring for complications such as hyperkalemia, metabolic acidosis, hyperphosphatemia, vitamin D deficiency, secondary hyperparathyroidism, and anemia 2.
- Referral to a nephrologist is recommended for patients with a GFR <30 mL/min/1.73 m2, severe albuminuria, or acute kidney injury 3, 5.
Age-Specific Considerations
- Age is a significant factor in CKD management, and older patients may have different outcomes and requirements than younger patients 6.
- Among patients with comparable levels of eGFR, older patients have higher rates of death and lower rates of end-stage renal disease than younger patients 6.
- The level of eGFR below which the risk of end-stage renal disease exceeds the risk of death varies by age, and older patients may require more individualized management plans 6.