From the Guidelines
Chronic Kidney Disease (CKD) is defined as abnormalities of kidney structure or function that are present for more than 3 months and have implications for health, with diagnosis requiring either kidney damage or decreased kidney function, specifically a glomerular filtration rate (GFR) <60 mL/min/1.73m², as stated in the most recent guideline 1. The diagnosis of CKD is based on the presence of kidney damage, typically detected through albuminuria with an albumin-to-creatinine ratio ≥30 mg/g, or decreased kidney function, with GFR being the best measure of overall kidney function in health and disease 1. CKD is further classified into five stages based on GFR levels:
- G1 (normal or high, ≥90 mL/min/1.73m²)
- G2 (mildly decreased, 60-89)
- G3 (moderately decreased, 30-59, with G3a being 45-59 and G3b being 30-44)
- G4 (severely decreased, 15-29)
- G5 (kidney failure, <15) 1. Additionally, CKD is categorized by albuminuria levels:
- A1 (normal to mildly increased, <30 mg/g)
- A2 (moderately increased, 30-300 mg/g)
- A3 (severely increased, >300 mg/g) 1. This staging system helps guide treatment decisions and predict outcomes, with the persistence of abnormalities for at least 3 months being crucial for diagnosis to distinguish CKD from acute kidney injury 1. Common causes of CKD include diabetes, hypertension, glomerulonephritis, and polycystic kidney disease, with the underlying pathophysiology involving progressive nephron loss and kidney scarring that reduces the kidneys' ability to filter waste, maintain electrolyte balance, and regulate blood pressure 1. The definition and classification of CKD have undergone significant developments, with the Kidney Disease: Improving Global Outcomes (KDIGO) guidelines providing a common system for definition and staging of CKD, which has facilitated comparisons between studies and increased research activities in patients with kidney disease not receiving long-term dialysis therapy 1.
From the Research
Definition of Chronic Kidney Disease (CKD)
- CKD is defined as a glomerular filtration rate (GFR) less than 60 mL/min/1.73 m2 or persistent evidence of kidney damage on imaging, biopsy, or urinalysis that persists for longer than 3 months 2, 3, 4.
- Kidney damage can be ascertained by the presence of albuminuria, defined as albumin-to-creatinine ratio >30 mg/g in two of three spot urine specimens 4.
Criteria for CKD
- The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation is the most accurate creatinine-based method for estimating GFR in routine practice 2.
- Cystatin C level measurement can be considered if patients have factors that might make creatinine-based equations inaccurate (eg, high or low muscle mass) 2.
- The presence of proteinuria is associated with increased risk of progression of CKD and death 3.
Classification of CKD
- CKD is classified into stages based on estimated GFR, degree of proteinuria, and the cause 2, 4.
- Kidney disease severity is classified into five stages according to the level of GFR 4.
Diagnosis and Screening
- CKD typically is asymptomatic but may be detected incidentally via urinalysis showing proteinuria or blood test results showing an elevated creatinine level 2.
- Screening should be considered if patients are at high risk of CKD (eg, patients with diabetes, hypertension, cardiovascular disease, family history of kidney failure) 2.
Management and Complications
- Management goals include mitigation of CKD risk factors to slow disease progression, including optimizing management of underlying conditions (eg, hypertension, diabetes) 2.
- Complications of CKD include anaemia, reduced red blood cell survival and iron deficiency, and mineral bone disease caused by disturbed vitamin D, calcium, and phosphate metabolism 3.