eGFR 18 Corresponds to Stage 4 Chronic Kidney Disease
An estimated glomerular filtration rate (eGFR) of 18 mL/min/1.73 m² indicates Stage 4 chronic kidney disease (CKD), which represents a severe decrease in kidney function. 1, 2
CKD Staging Based on eGFR
- Stage 1 CKD: eGFR ≥90 mL/min/1.73 m² with evidence of kidney damage 1, 2
- Stage 2 CKD: eGFR 60-89 mL/min/1.73 m² with evidence of kidney damage 1, 2
- Stage 3a CKD: eGFR 45-59 mL/min/1.73 m² (mild to moderate decrease) 1, 2
- Stage 3b CKD: eGFR 30-44 mL/min/1.73 m² (moderate to severe decrease) 1, 2
- Stage 4 CKD: eGFR 15-29 mL/min/1.73 m² (severe decrease) 1, 2
- Stage 5 CKD: eGFR <15 mL/min/1.73 m² or dialysis (kidney failure) 1, 2
Clinical Implications of Stage 4 CKD
With an eGFR of 18 mL/min/1.73 m², the patient has Stage 4 CKD, which carries significant clinical implications:
- High risk for progression to kidney failure (Stage 5) requiring renal replacement therapy 1, 3
- Increased risk of cardiovascular disease and mortality 1, 3
- Need for comprehensive evaluation and treatment of CKD complications 1
- Medication dosage adjustments are necessary due to reduced kidney function 1
- Referral to nephrology is strongly recommended at this stage 1, 2
Management Priorities for Stage 4 CKD
- Nephrology referral is essential at this stage for specialized care and planning for potential renal replacement therapy 1, 2
- Comprehensive evaluation of the cause of kidney injury is necessary 1, 2
- Treatment of modifiable risk factors for CKD progression (hypertension, diabetes, albuminuria) 1
- Assessment for complications such as anemia, metabolic bone disease, and electrolyte abnormalities 1
- Medication review and adjustment to avoid nephrotoxic drugs and adjust dosages appropriately 1
- Dietary modifications including protein restriction to approximately 0.8 g/kg body weight per day 2
- Preparation for potential renal replacement therapy (dialysis or transplantation) if kidney function continues to decline 1
Monitoring Parameters
- More frequent monitoring of eGFR and urinary albumin-to-creatinine ratio (UACR) is required (typically every 3-6 months) 1
- Regular monitoring of electrolytes, particularly potassium, calcium, and phosphorus 1, 2
- Blood pressure control is essential, with target individualized based on age and comorbidities 1
- Glycemic control in patients with diabetes 1
- Monitoring for signs of disease progression or complications 1, 2
Disease Trajectory and Prognosis
- Patients with Stage 4 CKD have varying trajectories of eGFR decline 4, 3
- Studies have identified different patterns of decline, including slow consistent decline, fast consistent decline, or variable patterns 3
- The annual rate of eGFR decline varies by underlying cause, with diabetic kidney disease and polycystic kidney disease often showing faster progression than other etiologies 5
- At Stage 4 CKD, the 1-year risk for progression to kidney failure is significantly higher than in earlier stages 3
- Mortality risk is also substantially elevated at this stage of kidney disease 3
Important Considerations and Pitfalls
- A single eGFR measurement of 18 mL/min/1.73 m² should be confirmed with repeat testing to establish chronicity (>3 months) before definitively classifying as Stage 4 CKD 1, 6
- The choice of eGFR estimation equation (MDRD vs. CKD-EPI) may slightly affect the calculated value, but would not change the stage classification for an eGFR of 18 1, 7
- Acute kidney injury should be ruled out by reviewing previous eGFR values and clinical context 1
- Certain medications and clinical states can temporarily affect serum creatinine and eGFR without reflecting true changes in kidney function 1, 7
- The presence and degree of albuminuria should be assessed alongside eGFR for comprehensive risk stratification 1