From the Guidelines
Chronic kidney disease (CKD) is classified into five stages based on estimated glomerular filtration rate (eGFR), which measures kidney function, with Stage 1 indicating normal kidney function but with evidence of kidney damage, Stage 2 representing mildly reduced kidney function, Stage 3 indicating moderately reduced kidney function, Stage 4 showing severely reduced kidney function, and Stage 5 representing kidney failure. The stages of CKD are defined as follows:
- Stage 1: eGFR ≥90 mL/min/1.73m², with evidence of kidney damage such as protein in urine 1
- Stage 2: eGFR 60-89 mL/min/1.73m², representing mildly reduced kidney function with some kidney damage 1
- Stage 3: divided into 3a (eGFR 45-59 mL/min/1.73m²) and 3b (eGFR 30-44 mL/min/1.73m²), both indicating moderately reduced kidney function 1
- Stage 4: eGFR 15-29 mL/min/1.73m², showing severely reduced kidney function 1
- Stage 5: eGFR <15 mL/min/1.73m², representing kidney failure, often requiring dialysis or transplantation 1 As CKD progresses, management becomes more intensive, focusing on blood pressure control with medications like ACE inhibitors or ARBs, blood sugar control in diabetics, dietary modifications (reduced sodium, potassium, and phosphorus), and treatment of complications such as anemia and bone disease, as outlined in the clinical action plan for each stage 1. Regular monitoring of kidney function, electrolytes, and urinary protein is essential for all CKD patients, with frequency increasing in advanced stages, and referral to a specialist is recommended for patients with a GFR less than 30 mL/min per 1.73 m² 1.
From the Research
Stages of Chronic Kidney Disease (CKD)
The stages of CKD are defined based on the severity of kidney function, which is assessed by estimating the glomerular filtration rate (GFR) 2. The US kidney disease outcomes quality initiative (KDOQI) guidelines indicate five stages of CKD:
- Stage 1: Kidney damage with normal or increased GFR
- Stage 2: Kidney damage with mild decrease in GFR
- Stage 3: Moderate decrease in GFR
- Stage 4: Severe decrease in GFR
- Stage 5: Kidney failure, also known as end-stage kidney disease (ESKD)
Classification and Diagnosis
CKD is classified into stages based on estimated GFR, degree of proteinuria, and the cause 3. The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation is the most accurate creatinine-based method for estimating GFR in routine practice 3, 4. Cystatin C level measurement can be considered if patients have factors that might make creatinine-based equations inaccurate 3.
Management and Treatment
The management of CKD patients is based on the stage of the disease 2, 5. Patients with mild renal damage (stage 1-2) can be managed by primary care physicians, while those with moderate-severe renal damage (stage 3-5) require the supervision of nephrologists 2. The treatment goals include mitigation of CKD risk factors to slow disease progression, such as optimizing management of underlying conditions (e.g., hypertension, diabetes) 3. Advanced CKD (stages 4 and 5) requires preparation for kidney replacement therapy and treatment of complications associated with chronic kidney failure 6.