What are the stages of Chronic Kidney Disease (CKD)?

Stages of Chronic Kidney Disease (CKD)

Chronic kidney disease is classified into five stages based primarily on glomerular filtration rate (GFR), with additional consideration of kidney damage markers such as albuminuria. 1

CKD Definition and Classification

CKD is defined as either kidney damage or decreased kidney function (GFR < 60 mL/min/1.73 m²) persisting for 3 or more months 1. The staging system developed by the National Kidney Foundation Kidney Disease Outcomes Quality Initiative (NKF K/DOQI) is as follows:

The Five Stages of CKD:

1. Stage 1: GFR ≥ 90 mL/min/1.73 m² with evidence of kidney damage

   • Kidney damage markers include persistent proteinuria, abnormal urine sediment, abnormalities in imaging studies
   • Normal or increased GFR but with evidence of kidney damage 1

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

   • Mildly decreased kidney function with evidence of kidney damage 1

3. Stage 3: GFR 30-59 mL/min/1.73 m²

   • Moderately decreased kidney function
   • At this stage, kidney damage markers are not required for diagnosis 1

4. Stage 4: GFR 15-29 mL/min/1.73 m²

   • Severely decreased kidney function
   • Preparation for renal replacement therapy should begin 1

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

   • Kidney failure (end-stage renal disease)
   • Usually accompanied by signs and symptoms of uremia
   • Renal replacement therapy (dialysis or transplantation) is typically needed 1

Important Clinical Considerations

Kidney Damage Markers

• Persistent proteinuria (albumin-creatinine ratio > 30 mg/g) is the principal marker of kidney damage 1
• Other markers include abnormalities in urine sediment, blood/urine chemistry, or imaging studies 1

Prevalence and Significance

• Approximately 11% of the U.S. adult population has CKD 1
• The prevalence of early stages (1-4) is more than 100 times greater than kidney failure (stage 5) 1
• CKD prevalence increases with age; about 17% of people over 60 years have GFR < 60 mL/min/1.73 m² 1

Risk Stratification

• KDIGO recommends a comprehensive CKD staging that incorporates both GFR and albuminuria for risk assessment 1
• At any GFR level, the degree of albuminuria is associated with risk of CKD progression, cardiovascular disease, and mortality 1

Clinical Action Plan by Stage

Each stage requires specific clinical actions:

• Stages 1-2: Diagnosis, treatment of comorbid conditions, slowing progression
• Stage 3: Above plus evaluation/treatment of complications
• Stage 4: Above plus preparation for renal replacement therapy
• Stage 5: Renal replacement therapy if uremia present 1

Common Pitfalls to Avoid

1. Relying solely on serum creatinine: Serum creatinine alone is an inadequate measure of kidney function as it varies with age, sex, muscle mass, and diet 2

2. Ignoring age-related GFR decline: While GFR declines with age, decreased GFR in the elderly is still an independent predictor of adverse outcomes and requires the same attention as in younger patients 1

3. Confusing kidney failure with ESRD: Kidney failure (stage 5 CKD) is not synonymous with end-stage renal disease (ESRD). ESRD is an administrative term indicating treatment with dialysis or transplantation 1

4. Missing early CKD: Less than 5% of patients with early CKD report awareness of their disease, highlighting the importance of screening at-risk populations 3

5. Overlooking albuminuria: Albuminuria is a powerful predictor of outcomes even with normal GFR and should be assessed in all patients with suspected CKD 1

By understanding and applying this staging system, clinicians can develop appropriate management plans to slow CKD progression, prevent complications, and improve patient outcomes.