Chronic Kidney Disease
Classification: An abnormality of kidney structure or function present for at least 3 months with implications for health, classified by cause, GFR category, and albuminuria category (CGA).
Key diagnostic discriminator: CKD requires chronicity plus reduced filtration and/or another marker of kidney damage; a single abnormal creatinine does not establish CKD.
Clinical priority: Identify the cause, quantify both GFR loss and albuminuria, and intervene before compensatory hyperfiltration drives additional nephron injury.
Common Causes and Risk Context
Common causes of CKD include diabetes, hypertension, chronic glomerular disease, inherited or structural kidney disease, recurrent obstruction, and prior severe or recurrent AKI. Risk assessment should therefore consider both the cause of kidney injury and evidence of ongoing damage such as albuminuria, abnormal urine sediment, structural abnormalities, or progressive GFR loss (KDIGO CKD Work Group, 2024; Perlman & Heung, 2019).
Pathophysiology of Progression
Irreversible nephron loss triggers compensatory enlargement and hyperfiltration of remaining nephrons. This preserves global filtration initially but increases intraglomerular pressure, protein trafficking, inflammation, fibrosis, and glomerulosclerosis. Progressive nephron loss then accelerates the same cycle (Perlman & Heung, 2019).
CGA Classification
KDIGO classifies CKD by Cause, GFR category, and Albuminuria category (CGA). G1 and G2 do not establish CKD by themselves; another marker of kidney damage must be present if eGFR is ≥60 mL/min/1.73 m² (KDIGO CKD Work Group, 2024).
| Albuminuria category | Urine ACR | Description |
| A1 | <30 mg/g | Normal to mildly increased |
| A2 | 30–299 mg/g | Moderately increased |
| A3 | ≥300 mg/g | Severely increased |
Why GFR and Albuminuria Must Be Interpreted Together
KDIGO prognosis is based on both GFR category and albuminuria category rather than either measure alone. At any given eGFR, greater albuminuria identifies higher risk for CKD progression and cardiovascular complications; likewise, lower GFR increases risk even when albuminuria is modest. This is why CGA classification is more informative than describing a patient only as “stage 3 CKD” (KDIGO CKD Work Group, 2024).
Systemic Consequences
As renal reserve declines, the kidneys become progressively less able to regulate sodium, water, potassium, acid-base balance, erythropoietin production, and mineral metabolism. Sodium-water retention contributes to hypertension and edema. Hyperkalemia and metabolic acidosis emerge when compensation fails. Reduced erythropoietin contributes to normocytic anemia. Phosphate retention and reduced vitamin D activation promote secondary hyperparathyroidism and CKD-mineral and bone disorder (KDIGO CKD Work Group, 2024; Perlman & Heung, 2019).
Advanced renal dysfunction can produce uremia, a systemic syndrome involving retained solutes, metabolic abnormalities, and loss of endocrine function. Manifestations may include anorexia, pruritus, cognitive change, neuromuscular symptoms, bleeding tendency, and pericardial involvement (KDIGO CKD Work Group, 2024; Perlman & Heung, 2019).
Diagnostic Approach
- Confirm persistence for at least 3 months using prior creatinine/eGFR, urine studies, imaging, or known structural disease (KDIGO CKD Work Group, 2024; Perlman & Heung, 2019).
- Assess filtration with serum creatinine and eGFR trends (KDIGO CKD Work Group, 2024; Perlman & Heung, 2019).
- Assess kidney damage with urine albumin-to-creatinine ratio (ACR); KDIGO prefers a first-morning midstream specimen when practical (KDIGO CKD Work Group, 2024; Perlman & Heung, 2019).
- Use urinalysis, imaging, serologic testing, or biopsy when needed to identify the cause (KDIGO CKD Work Group, 2024; Perlman & Heung, 2019).
- Evaluate complications including potassium, bicarbonate, hemoglobin/iron status, calcium, phosphorus, PTH, blood pressure, and volume status as disease severity warrants (KDIGO CKD Work Group, 2024; Perlman & Heung, 2019).
Clinical Manifestations
Early CKD is often asymptomatic. With progression, findings may include hypertension, edema, fatigue, anemia, electrolyte and acid-base abnormalities, CKD-mineral and bone disorder, pruritus, anorexia, cognitive or neuromuscular symptoms, and other manifestations of uremia (Perlman & Heung, 2019; Schonder, 2026).
Findings That Argue for an Acute or Alternative Process
An abrupt creatinine rise, rapidly changing urine output, or sudden electrolyte derangement should raise concern for superimposed AKI rather than assuming progression of CKD. Conversely, chronic anemia, mineral-bone abnormalities, longstanding albuminuria, structural abnormalities, or small echogenic kidneys support chronicity. G1 or G2 filtration categories alone do not establish CKD without another marker of kidney damage (KDIGO CKD Work Group, 2024; Perlman & Heung, 2019).
Differential Diagnosis
Evaluation should distinguish chronic progressive kidney disease from AKI, recurrent obstruction, glomerular disease, renovascular disease, inherited structural disease, and systemic disorders such as diabetes or autoimmune disease. Cause is part of the CGA classification and should not be replaced by staging alone (KDIGO CKD Work Group, 2024).
Treatment Principles
Management aims to treat the cause, reduce progression risk, control blood pressure and albuminuria, manage cardiovascular risk, avoid nephrotoxins, and treat complications such as volume overload, hyperkalemia, acidosis, anemia, and mineral-bone abnormalities. Advanced disease requires planning for kidney replacement therapy or conservative kidney management according to prognosis and patient goals (KDIGO CKD Work Group, 2024; Schonder, 2026).
Red Flags
- Rapid loss of kidney function or suspected AKI superimposed on CKD (KDIGO CKD Work Group, 2024; Perlman & Heung, 2019).
- Refractory hyperkalemia, acidosis, pulmonary edema, or symptomatic uremia (KDIGO CKD Work Group, 2024; Perlman & Heung, 2019).
- Nephritic urinary sediment, rapidly increasing proteinuria, or systemic features suggesting an active glomerular process (KDIGO CKD Work Group, 2024; Perlman & Heung, 2019).
- Symptoms or complications suggesting kidney failure that require urgent nephrology assessment (KDIGO CKD Work Group, 2024).
High-Yield Distinctions
- CKD requires persistence for ≥3 months.
- Albuminuria is both a marker of kidney damage and a predictor of progression.
- Nephron hyperfiltration is initially adaptive and later injurious.
- CKD is systemic: think volume, potassium, acid-base, anemia, mineral-bone disease, cardiovascular risk, and uremia.
- CKD increases susceptibility to AKI; the two can coexist.
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References
Kidney Disease: Improving Global Outcomes (KDIGO) CKD Work Group. (2024). KDIGO 2024 clinical practice guideline for the evaluation and management of chronic kidney disease. Kidney International, 105(4S), S117–S314. https://doi.org/10.1016/j.kint.2023.10.018
Perlman, R. L., & Heung, M. (2019). Renal disease. In G. D. Hammer & S. J. McPhee (Eds.), Pathophysiology of disease: An introduction to clinical medicine (8th ed., pp. 493–518). McGraw-Hill Education.
Schonder, K. S. (2026). Chronic and end-stage kidney disease. In M. A. Chisholm-Burns, P. M. Malone, J. M. Kolesar, K. C. Lee, P. B. Bookstaver, & K. R. Matthias (Eds.), Pharmacotherapy principles & practice (7th ed.). McGraw Hill.