What are the implications and management strategies for an adult patient with an estimated Glomerular Filtration Rate (eGFR) of 66, indicating mildly decreased kidney function?

eGFR of 66 mL/min/1.73 m²: Classification and Management

An eGFR of 66 mL/min/1.73 m² represents CKD Stage 2 (mildly decreased kidney function) and requires annual monitoring, cardiovascular risk assessment, and identification of the underlying cause to prevent progression. 1, 2

Classification and Risk Stratification

Your eGFR of 66 mL/min/1.73 m² falls into CKD Stage G2 (60-89 mL/min/1.73 m²), which is classified as mildly decreased kidney function. 1, 2 However, this diagnosis requires evidence of kidney damage (such as albuminuria, structural abnormalities, or other markers) to be present for at least 3 months. 1 Without evidence of kidney damage, this eGFR alone does not constitute CKD. 1

The next critical step is measuring albuminuria (urine albumin-to-creatinine ratio or UACR) to determine your true CKD risk category:

• If UACR <3 mg/mmol (<30 mg/g): You are at low risk and may not have CKD unless other markers of kidney damage are present 1
• If UACR 3-30 mg/mmol (30-300 mg/g): You are at moderate risk 1
• If UACR >30 mg/mmol (>300 mg/g): You are at high risk 1

Cardiovascular Risk Assessment

Mildly reduced kidney function at this level is independently associated with increased cardiovascular disease risk and mortality. 3 Even at eGFR 60-69 mL/min/1.73 m², patients demonstrate higher coronary artery calcium scores, elevated cardiac biomarkers (BNP and GDF-15), and a 40-45% increased risk of cardiovascular events over 16 years compared to those with eGFR ≥90. 3

You should be considered in the highest risk group for cardiovascular disease, and aggressive cardiovascular risk factor management is warranted. 1

Required Monitoring

Annual monitoring is the minimum standard at this eGFR level:

• Serum creatinine and eGFR calculation annually 2
• Urine albumin-to-creatinine ratio (UACR) annually 2
• Blood pressure at every clinical visit with target <130/80 mmHg 2

Increase monitoring frequency to every 6 months if:

• Progressive decline in eGFR is detected 2
• You have diabetes 2
• UACR is elevated 2

Medication Management

At eGFR 66 mL/min/1.73 m², most medications do not require dose adjustment. 2 However, specific considerations include:

• ACE inhibitors or ARBs: Use at standard doses if hypertension or albuminuria is present, with appropriate monitoring for hyperkalemia and acute eGFR decline 2
• Fenofibrate: Can be used at normal doses (dose reduction only required when eGFR <60) 2
• NSAIDs: Avoid prolonged use due to nephrotoxic potential 2

Prevention of Progression

The primary goal is preventing progression to eGFR <60 mL/min/1.73 m², which marks a critical threshold where complications of CKD substantially increase. 1

Key interventions to slow progression:

• Blood pressure control to <130/80 mmHg, preferably with ACE inhibitors or ARBs if albuminuria is present 2
• Optimize glycemic control if diabetic (HbA1c target individualized but generally <7%) 2
• Address cardiovascular risk factors: smoking cessation, weight management, regular physical activity 2
• Avoid nephrotoxic medications, particularly NSAIDs and certain antibiotics 2
• Identify and treat the underlying cause of kidney disease 1

When to Refer to Nephrology

Nephrology referral is NOT routinely required at eGFR 66 unless specific concerning features are present. 1

Refer to nephrology if any of the following occur:

• Rapid decline in eGFR (>5 mL/min/1.73 m² per year or >10 mL/min/1.73 m² over 5 years) 2, 4
• Significant proteinuria (UACR ≥300 mg/g or ≥30 mg/mmol) 1, 2
• Difficult-to-control hypertension requiring ≥4 antihypertensive agents 1
• Unexplained hematuria (>20 RBCs per high-power field) or red cell casts 1
• Suspected non-diabetic kidney disease or unclear etiology 2
• Persistent electrolyte abnormalities (particularly hyperkalemia) 1

Critical Monitoring Thresholds

Watch for progression to eGFR <60 mL/min/1.73 m², as this represents Stage 3 CKD where:

• Complications of CKD (anemia, bone disease, metabolic acidosis) become prevalent 1
• Cardiovascular risk increases substantially 1
• More intensive monitoring and intervention are required 1
• The likelihood of multiple comorbidities increases dramatically 1

A decline of ≥30% in eGFR over 2 years is strongly associated with progression to kidney failure (10-year risk of ESRD increases from 18% to 64%) and should trigger immediate nephrology referral. 4

Age Considerations

If you are ≥65 years old, recognize that age-related GFR decline may result in overestimation of CKD risk at this eGFR level. 1 However, decreased eGFR remains an independent predictor of adverse outcomes including death and cardiovascular disease regardless of age, and the same management principles apply. 1