What are the stages of renal disease based on glomerular filtration rate (GFR) and how are they managed?

Chronic Kidney Disease Staging

Chronic kidney disease is classified into five stages based on glomerular filtration rate (GFR), with abnormalities of kidney structure or function persisting for at least 3 months, and should be further categorized by albuminuria level for complete risk stratification. 1, 2

The Five CKD Stages

Stage 1: GFR ≥90 mL/min/1.73 m²

• Requires evidence of kidney damage (such as albuminuria, proteinuria, hematuria, pathological abnormalities on biopsy, or imaging abnormalities) in addition to the GFR value for diagnosis 1, 3, 2
• GFR alone is insufficient at this level—you must document structural or functional kidney damage 3
• Focus management on diagnosing and treating underlying conditions, slowing progression, and reducing cardiovascular disease risk 2
• Even with normal GFR, this stage carries increased risk for cardiovascular disease and mortality 3

Stage 2: GFR 60-89 mL/min/1.73 m²

• Also requires evidence of kidney damage for diagnosis, similar to Stage 1 1, 3, 2
• Emphasize estimating the rate of disease progression 2
• Stages 1 and 2 are considered stable and warrant annual monitoring 4

Stage 3: GFR 30-59 mL/min/1.73 m²

• This stage is subdivided into 3a and 3b based on significantly different mortality and cardiovascular risk profiles 1, 2
  • Stage 3a: GFR 45-59 mL/min/1.73 m² (slightly to moderately decreased) 4, 1, 2
  • Stage 3b: GFR 30-44 mL/min/1.73 m² (moderately decreased) 4, 1, 2
• GFR criteria alone are sufficient for diagnosis at this stage and beyond—evidence of kidney damage is not required 3
• Begin intensive evaluation and treatment of complications (hypertension, anemia, hyperphosphatemia) 1, 2
• Risk of complications increases significantly below GFR of 60 mL/min/1.73 m² 2
• Follow-up with biological control should occur 2-4 times per year based on severity 4

Stage 4: GFR 15-29 mL/min/1.73 m²

• Represents severe decrease in kidney function 1, 3, 2
• Requires intensive management of complications and preparation for kidney replacement therapy 1, 2
• Refer to nephrologist for consultation and co-management 2
• Hypertension prevalence approaches 80% at this stage 1
• The likelihood of having multiple complications increases substantially 1

Stage 5: GFR <15 mL/min/1.73 m² or on dialysis

• Represents end-stage renal failure or kidney failure 4, 1, 3, 2
• Kidney replacement therapy (dialysis or transplantation) is indicated if uremic symptoms develop 1, 2

Critical Diagnostic Requirements

GFR Estimation

• Use the CKD-EPI equation for reporting estimated GFR in adults, as it demonstrates less bias than the MDRD equation, especially at GFR ≥60 mL/min/1.73 m², with improved precision and greater accuracy 1
• Never rely on serum creatinine alone—always calculate estimated GFR accounting for age, sex, race, and body size 1
• All abnormalities must persist for at least 3 months to distinguish chronic from acute kidney disease 1, 3, 2

Albuminuria Classification

• Albuminuria must be assessed alongside GFR for complete risk stratification using the CGA classification (Cause, GFR category, Albuminuria category) 1, 2
• Three albuminuria categories exist: A1 (normal to mildly increased, <30 mg/g), A2 (moderately increased, 30-300 mg/g), and A3 (severely increased, >300 mg/g) 4, 1
• An albuminuria level of 30 mg/g represents more than 3 times the normal value and independently predicts increased risk for CKD complications, cardiovascular mortality, and progression to kidney failure 1
• Measure the albumin-to-creatinine ratio (ACR) on a single urine sample rather than 24-hour urine collection, and perform at least 2-3 measurements over 6 months to confirm diagnosis 4

Common Pitfalls to Avoid

• Do not classify using GFR alone—always use the complete CGA system to avoid incomplete staging 1
• Relying solely on serum creatinine without calculating estimated GFR leads to missed diagnoses, especially in elderly patients or those with reduced muscle mass 3
• Do not dismiss age-related decline in GFR as "normal aging"—decreased GFR in the elderly remains an independent predictor of adverse outcomes 2
• There is no correlation between GFR and albuminuria progression, so both parameters must be monitored independently 4
• All GFR estimation formulas underestimate GFR for subnormal renal function (GFR <90 mL/min) 4