Stages of Chronic Kidney Disease
Chronic Kidney Disease (CKD) is classified into five stages based on glomerular filtration rate (GFR) and evidence of kidney damage, with additional subcategorization by albuminuria level to better assess risk and guide treatment decisions. 1
GFR Categories
| Stage | GFR (mL/min/1.73 m²) | Description |
|---|---|---|
| G1 | ≥90 | Normal or elevated (with evidence of kidney damage) |
| G2 | 60-89 | Mildly decreased (with evidence of kidney damage) |
| G3a | 45-59 | Mildly to moderately decreased |
| G3b | 30-44 | Moderately to severely decreased |
| G4 | 15-29 | Severely decreased |
| G5 | <15 | Kidney failure |
Albuminuria Categories
| Category | Albumin-to-Creatinine Ratio (mg/g) | Description |
|---|---|---|
| A1 | <30 | Normal to mildly increased |
| A2 | 30-300 | Moderately increased |
| A3 | >300 | Severely increased |
Comprehensive CKD Classification
CKD is diagnosed by the persistent presence of elevated urinary albumin excretion (albuminuria), low estimated glomerular filtration rate (eGFR), or other manifestations of kidney damage for at least 3 months 2, 1.
- Stages 1-2: Defined by evidence of kidney damage (usually albuminuria) with eGFR ≥60 mL/min/1.73 m²
- Stages 3-5: Defined by progressively lower ranges of eGFR, with or without evidence of kidney damage 2
Clinical Focus by CKD Stage
| Stage | GFR (mL/min/1.73 m²) | Clinical Focus |
|---|---|---|
| 1 | ≥90 | Diagnosis, risk reduction, treating comorbidities |
| 2 | 60-89 | Slowing progression, CVD risk reduction |
| 3 | 30-59 | Evaluating complications, estimating progression |
| 4 | 15-29 | Managing complications, preparing for replacement therapy |
| 5 | <15 | Replacement therapy if uremia present |
The KDIGO (Kidney Disease: Improving Global Outcomes) recommends a comprehensive CKD staging system that incorporates albuminuria at all stages of eGFR, as this provides better risk stratification for CKD progression, cardiovascular disease, and mortality 2.
Key Management Considerations by Stage
Stage 1:
- Diagnose cause of kidney injury
- Evaluate and treat risk factors for CKD progression
- Focus on prevention
Stage 2:
- Continue Stage 1 interventions
- Implement strategies to slow progression
- Address cardiovascular risk factors
Stage 3:
- Continue previous interventions
- Begin evaluation for complications
- More frequent monitoring of kidney function
Stage 4:
- Manage complications (anemia, bone disorders, etc.)
- Prepare for renal replacement therapy
- Consider nephrology referral if not already done
Stage 5:
Important Clinical Considerations
At any stage of CKD, the degree of albuminuria, observed history of eGFR loss, and cause of kidney damage should be used to characterize CKD, gauge prognosis, and guide treatment decisions 2
Regular monitoring of GFR, albuminuria, and other parameters is essential, with frequency depending on disease stage and comorbidities 1
Risk factors for CKD progression include elevated blood pressure, hyperglycemia, and albuminuria 2
The eGFR is best calculated using the CKD-EPI creatinine equation without the race variable 3
Blood pressure control (target <130/80 mmHg) is recommended to reduce CKD progression risk 1
By understanding and applying this staging system, clinicians can better assess risk, monitor progression, and implement appropriate interventions to slow disease advancement and manage complications in patients with CKD.