How should I evaluate and manage a 44-year-old woman with an estimated glomerular filtration rate of 64 mL/min/1.73 m²?

Evaluation and Management of eGFR 64 mL/min/1.73 m² in a 44-Year-Old Woman

This eGFR of 64 mL/min/1.73 m² indicates Stage G2 chronic kidney disease (mild reduction in kidney function with kidney damage) or normal kidney function if no other markers of kidney damage are present, and requires confirmation of chronicity, assessment for albuminuria, and identification of the underlying cause. 1

Confirm the Diagnosis

• Repeat the eGFR measurement within 3 months to verify chronicity, because CKD is defined by persistent abnormalities for ≥3 months. 2
• Do not rely on serum creatinine alone; always calculate and use eGFR for assessment of kidney function. 2
• Consider measuring cystatin C-based eGFR if the creatinine-based estimate seems discordant with the clinical picture, as creatinine estimates are inaccurate in approximately 16-20% of individuals. 2
• An eGFR ≥60 mL/min/1.73 m² does not meet criteria for CKD unless albuminuria ≥30 mg/g creatinine or other markers of kidney damage are present. 3

Essential Initial Workup

• Measure urine albumin-to-creatinine ratio (UACR) in a random spot urine collection to assess for albuminuria, as this is the most practical screening method. 1
• Screen for blood pressure abnormalities, electrolyte disturbances, and assess volume status. 2
• Obtain a detailed history focusing on:
  • Diabetes mellitus (duration, control, complications) 1
  • Hypertension (duration, control, medication history) 1
  • Autoimmune diseases (lupus, scleroderma, rheumatoid arthritis) 1
  • Medication exposure (NSAIDs, nephrotoxic drugs) 2
  • Family history of kidney disease 1
  • Recurrent urinary tract infections or kidney stones 1

Classification and Risk Stratification

• With an eGFR of 64 mL/min/1.73 m², this patient falls into Stage G2 (60-89 mL/min/1.73 m²) if kidney damage is present, or has normal kidney function if no damage markers exist. 1
• If UACR is <30 mg/g and no other kidney damage markers are present, this patient does not have CKD and requires only routine monitoring. 3
• If UACR is ≥30 mg/g, this confirms CKD Stage G2A2 or higher, which carries increased cardiovascular risk and requires intervention. 4

Management Based on Findings

If CKD is Confirmed (UACR ≥30 mg/g or other damage markers):

Blood Pressure Management:

• Target blood pressure <130/80 mmHg. 2
• Use ACE inhibitor or ARB as first-line therapy if albuminuria is present, regardless of hypertension status. 1, 2
• Monitor serum creatinine and potassium 2-4 weeks after initiating ACE inhibitor/ARB therapy. 2

Medication Review:

• Strictly avoid NSAIDs, as they reduce renal blood flow and can precipitate acute kidney injury. 2
• Review all medications for appropriate dosing, though most drugs do not require adjustment until eGFR <60 mL/min/1.73 m². 2

Dietary Modifications:

• Restrict sodium to <2 g/day to reduce blood pressure and slow progression. 2
• At this eGFR level, protein restriction is not yet indicated (reserved for eGFR <45 mL/min/1.73 m²). 2

Monitoring Frequency:

• Measure eGFR and UACR at least annually. 2
• More frequent monitoring (every 6 months) if UACR ≥300 mg/g or eGFR is declining. 1

If No CKD is Confirmed (UACR <30 mg/g, no damage markers):

• Repeat eGFR and UACR annually to monitor for development of kidney disease. 2
• Address cardiovascular risk factors (hypertension, diabetes, smoking, dyslipidemia). 4
• No specific kidney-protective interventions are required at this time. 3

When to Refer to Nephrology

• Do not refer at this eGFR level unless specific concerning features are present. 1, 2
• Refer promptly if any of the following are present:
  • Uncertainty about the etiology of kidney disease 1, 2
  • UACR ≥300 mg/g (nephrotic-range proteinuria) 2
  • Rapidly progressing kidney disease (eGFR decline >5 mL/min/1.73 m² per year) 1, 2
  • Difficult-to-control hypertension despite multiple agents 1
  • Active urinary sediment (hematuria with dysmorphic RBCs or RBC casts) 1

Critical Pitfalls to Avoid

• Do not dismiss an eGFR of 64 mL/min/1.73 m² as "normal" without checking for albuminuria—kidney damage can be present even with preserved eGFR. 3
• Do not use serum creatinine alone to assess kidney function, as it is affected by muscle mass, age, sex, and race independent of GFR. 2, 3
• Do not overlook cardiovascular risk assessment, as even mild CKD markedly increases cardiovascular disease risk. 1, 4
• In a 44-year-old woman, an eGFR of 64 mL/min/1.73 m² is below the expected normal range for her age (normal GFR is approximately 130 mL/min/1.73 m² with a mean decline of 0.75 mL/min/year starting in the third or fourth decade), warranting thorough investigation for underlying causes. 3

Special Considerations for Young Adults

• CKD at age 44 is uncommon and suggests an underlying etiology that requires identification (diabetes, hypertension, glomerulonephritis, genetic kidney disease, or chronic medication exposure). 1
• Early identification and treatment of the underlying cause is critical to prevent progression to advanced CKD and ESRD. 1, 5
• Even a 30% decline in eGFR over 2 years is strongly associated with progression to ESRD and mortality, emphasizing the importance of close monitoring. 5