Chronic Kidney Disease vs Chronic Renal Failure: Terminology and Clinical Distinction
Chronic kidney disease (CKD) is the modern, comprehensive term that encompasses all stages of kidney dysfunction, while chronic renal failure (CRF) is an outdated term that historically referred only to advanced kidney disease requiring dialysis or transplantation. 1
Key Terminological Evolution
CKD represents a paradigm shift from the older "chronic renal failure" terminology by including early stages of kidney dysfunction that were previously unrecognized. 2, 3 The National Kidney Foundation's K/DOQI guidelines established CKD as the standard nomenclature to capture the full spectrum of kidney disease, from early damage with preserved function through end-stage kidney failure. 1, 4
Why the Terminology Changed
CRF traditionally described only symptomatic, advanced kidney disease (typically GFR <30 mL/min/1.73 m²) when patients developed uremic symptoms and complications. 5
CKD was introduced to identify patients earlier in the disease process when interventions can prevent progression and reduce cardiovascular mortality, which kills most CKD patients before they reach kidney failure. 1, 6
The prevalence of early CKD stages (stages 1-4) is more than 100 times greater than kidney failure (stage 5), making early detection critical for public health impact. 1
Modern CKD Definition and Classification
CKD is defined as either kidney damage OR GFR <60 mL/min/1.73 m² persisting for 3 or more months, regardless of cause. 1, 7 This definition includes:
Diagnostic Criteria (Either One Sufficient)
Kidney damage markers: Persistent albuminuria (albumin-to-creatinine ratio ≥30 mg/g), abnormal urine sediment, structural abnormalities on imaging, or abnormal kidney histology. 1, 7
Decreased kidney function: GFR <60 mL/min/1.73 m² for ≥3 months, which represents loss of half or more of normal adult kidney function. 1
Five-Stage Classification System
The National Kidney Foundation K/DOQI classification stratifies CKD by GFR level 4:
- Stage 1: GFR ≥90 mL/min/1.73 m² with evidence of kidney damage (requires markers like albuminuria). 4
- Stage 2: GFR 60-89 mL/min/1.73 m² with evidence of kidney damage. 4
- Stage 3a: GFR 45-59 mL/min/1.73 m². 4
- Stage 3b: GFR 30-44 mL/min/1.73 m². 4
- Stage 4: GFR 15-29 mL/min/1.73 m² (this approximates what was historically called "chronic renal failure"). 4, 8
- Stage 5: GFR <15 mL/min/1.73 m² or kidney failure requiring dialysis. 4
What Constitutes "Kidney Failure" in Modern Terminology
Kidney failure is specifically defined as either GFR <15 mL/min/1.73 m² with uremic symptoms OR the need to start kidney replacement therapy (dialysis or transplantation). 1 This corresponds to CKD Stage 5 and is the closest modern equivalent to what was previously called "chronic renal failure" or "end-stage renal disease." 1
Important Distinction: Kidney Failure vs ESRD
Kidney failure is a clinical diagnosis based on kidney function and symptoms. 1
End-stage renal disease (ESRD) is an administrative term in the United States indicating a patient is receiving dialysis or transplantation for Medicare payment purposes, not a precise clinical definition. 1
ESRD does not include patients with kidney failure who are not treated with dialysis or transplantation, making it less useful clinically than the kidney failure designation. 1
Clinical Implications of the Terminology Shift
Why Early Stage Recognition Matters
Decreased GFR is an independent predictor of death and cardiovascular disease, even in elderly patients where decline was previously dismissed as "normal aging." 1
Complications of CKD (hypertension, anemia, malnutrition, bone disease, neuropathy) begin when GFR falls below 60 mL/min/1.73 m² and can be prevented or ameliorated with early treatment. 1, 6
Cardiovascular events are more common than progression to kidney failure in CKD patients, making early identification crucial for CV risk reduction. 1, 6
Practical Management Differences
Patients with CKD Stage 4 (GFR <30 mL/min/1.73 m²) require nephrology referral for preparation for kidney replacement therapy. 4, 8
All CKD stages require drug dosage adjustments, not just advanced kidney failure. 1
Treatment goals differ by stage: early stages focus on slowing progression and CV risk reduction, while advanced stages (the old "CRF" territory) focus on managing complications and preparing for dialysis. 4
Common Pitfall to Avoid
Do not diagnose CKD in patients with GFR ≥60 mL/min/1.73 m² unless they have documented kidney damage markers (such as albuminuria or structural abnormalities). 7, 2 A common error is labeling patients with normal kidney function as having CKD without evidence of actual kidney damage, which can have negative consequences for insurance and creates confusion about the diagnosis. 2