What are the stages and management of chronic kidney disease (CKD)?

Chronic Kidney Disease Staging

CKD is classified into five stages based on GFR, with Stage 3 subdivided into 3a and 3b, and must incorporate both GFR category and albuminuria category (CGA classification) for complete risk stratification. 1

CKD Staging System

GFR-Based Stages

• Stage 1: GFR ≥90 mL/min/1.73 m² with evidence of kidney damage (albuminuria, proteinuria, or structural abnormalities on imaging) 2, 3

• Stage 2: GFR 60-89 mL/min/1.73 m² with evidence of kidney damage 2, 3

• Stage 3a: GFR 45-59 mL/min/1.73 m² (moderate decrease in kidney function) 1, 2, 3

• Stage 3b: GFR 30-44 mL/min/1.73 m² (moderate to severe decrease) 1, 2, 3

• Stage 4: GFR 15-29 mL/min/1.73 m² (severe decrease in kidney function) 2, 4, 3

• Stage 5: GFR <15 mL/min/1.73 m² or dialysis (kidney failure) 2, 4, 3

The subdivision of Stage 3 into 3a and 3b was driven by data demonstrating different outcomes and risk profiles between these GFR ranges, particularly regarding cardiovascular mortality, acute kidney injury risk, and CKD progression. 1

Critical Diagnostic Requirements

• For Stages 1-2: Evidence of kidney damage (such as albuminuria ≥30 mg/g) is mandatory for diagnosis, as GFR alone is insufficient 2, 3

• For Stages 3-5: Diagnosis can be made based on GFR alone without additional markers of kidney damage 2

• Duration requirement: Abnormalities must persist for at least 3 months to confirm CKD diagnosis 2, 3, 5

Albuminuria Categories (Essential Component)

The CGA classification system mandates assessing albuminuria alongside GFR for complete risk stratification. 1

• A1: Normal to mildly increased albuminuria (ACR <30 mg/g) 2

• A2: Moderately increased albuminuria (ACR 30-300 mg/g) 2

• A3: Severely increased albuminuria (ACR >300 mg/g) 2

An ACR of 30 mg/g represents more than 3 times the normal value in young adults and independently predicts increased risk for CKD complications, cardiovascular mortality, and progression to kidney failure. 1

GFR Estimation Method

• Use the CKD-EPI equation for reporting estimated GFR in adults from serum creatinine calibrated to isotope-dilution mass spectrometry reference method 1, 6

• The CKD-EPI equation demonstrates less bias than the MDRD equation, especially at GFR ≥60 mL/min/1.73 m², with improved precision and greater accuracy 1

• Do not rely on serum creatinine alone—always use prediction equations accounting for age, sex, race, and body size 2, 3, 6

• For borderline cases (eGFR 45-59 mL/min/1.73 m² without other markers of kidney damage), measure cystatin C to confirm CKD diagnosis 1

Stage-Specific Management Approach

Stages 1-2 Management

• Focus on early detection, CKD risk reduction, and treating comorbid conditions (diabetes, hypertension) 2

• Initiate cardiovascular disease risk reduction strategies 3

• Slow progression through blood pressure control (target <130/80 mmHg) and glycemic control in diabetics 4

Stage 3 Management

• Estimate progression rate and begin systematic evaluation for complications 2

• For albuminuria ≥30 mg/g: Initiate ACE inhibitors or ARBs, especially in diabetic kidney disease 4

• Monitor for emerging complications as risk increases significantly below GFR 60 mL/min/1.73 m² 2, 3

Stage 4 Management

• Mandatory nephrology referral for all patients with GFR <30 mL/min/1.73 m² 4, 3, 7

• Intensive management of complications including anemia (monitor hemoglobin, consider iron supplementation), hyperkalemia, metabolic acidosis, hyperphosphatemia, vitamin D deficiency, and secondary hyperparathyroidism 4, 5

• Begin preparation for kidney replacement therapy 2, 3

• Hypertension prevalence approaches 80% at this stage and requires aggressive management 2

Stage 5 Management

• Initiate kidney replacement therapy (dialysis or transplantation) if uremic symptoms develop 2, 3

• Continue intensive complication management 4

Common Pitfalls to Avoid

• Late nephrology referral: Refer no later than Stage 4 (GFR <30 mL/min/1.73 m²)—earlier referral for rapid GFR decline (>5 mL/min/1.73 m² per year) or albuminuria ≥300 mg/24 hours 4, 5

• Incomplete staging: Always classify using the complete CGA system (Cause, GFR category, Albuminuria category), not GFR alone 1

• Nephrotoxin exposure: Avoid NSAIDs and adjust dosing for renally cleared medications (antibiotics, oral hypoglycemics) 5

• Dismissing age-related GFR decline: GFR <60 mL/min/1.73 m² remains an independent predictor of adverse outcomes regardless of age and should not be considered "normal aging" 3

• Single measurement diagnosis: Confirm abnormalities persist for ≥3 months before diagnosing CKD 2, 3, 5