Understanding Kidney Disease
Kidney disease is defined as abnormalities in kidney structure or function that have implications for health, and includes both acute and chronic conditions with varying degrees of severity based on glomerular filtration rate (GFR) and evidence of kidney damage. 1
Types of Kidney Disease
Acute Kidney Diseases and Disorders (AKD)
- Definition: Abnormalities in kidney structure or function present for ≤3 months 1
- Includes:
- Acute Kidney Injury (AKI): Sudden decrease in kidney function manifested by:
- Increase in serum creatinine within 48 hours to 7 days
- Oliguria (reduced urine output)
- AKD without AKI: Disorders with markers of kidney damage (hematuria, pyuria, urinary tract obstruction) without rapid GFR decline 1
- Acute Kidney Injury (AKI): Sudden decrease in kidney function manifested by:
- Staging of AKI:
- Stage 1: Mild
- Stage 2: Moderate
- Stage 3: Severe (may require dialysis, denoted as Stage 3D) 1
Chronic Kidney Disease (CKD)
- Definition: Abnormalities in kidney structure or function present for >3 months 1, 2
- Diagnostic Criteria:
- GFR <60 mL/min/1.73 m² for >3 months, and/or
- Evidence of kidney damage (proteinuria/albuminuria, abnormal urinary sediment, abnormal imaging) 2
Classification of CKD
GFR Categories (G1-G5)
| Category | GFR (mL/min/1.73 m²) | Description |
|---|---|---|
| G1 | ≥90 | Normal or elevated |
| G2 | 60-89 | Mildly decreased |
| G3a | 45-59 | Mildly to moderately decreased |
| G3b | 30-44 | Moderately to severely decreased |
| G4 | 15-29 | Severely decreased |
| G5 | <15 | Kidney failure |
| [2] |
Albuminuria Categories (A1-A3)
| Category | Albumin-to-Creatinine Ratio (mg/g) | Description |
|---|---|---|
| A1 | <30 | Normal to mildly increased |
| A2 | 30-300 | Moderately increased |
| A3 | >300 | Severely increased |
| [2] |
Kidney Failure
Kidney failure (formerly called end-stage renal disease) is defined as:
- GFR <15 mL/min/1.73 m² or treatment by dialysis 1
- May be acute (≤3 months) or chronic (>3 months)
- Can present with or without symptoms (uremic syndrome)
Treatment Options for Kidney Failure
- Kidney Replacement Therapy (KRT):
- Dialysis:
- Hemodialysis (HD)
- Peritoneal dialysis (PD)
- Kidney transplantation:
- Living donor (LDKT)
- Deceased donor (DDKT) 1
- Dialysis:
- Conservative care (for those not receiving KRT)
Causes of Kidney Disease
Kidney disease can result from various causes:
- Diabetes - leading cause of CKD worldwide 3
- Hypertension - second most common cause 3, 4
- Glomerulonephritis - inflammation of the kidney's filtering units
- Polycystic kidney disease - genetic disorder causing cysts in kidneys
- Urinary tract obstruction
- Medications (nephrotoxic drugs)
- Autoimmune diseases (lupus, vasculitis)
Complications of Kidney Disease
As kidney function declines, various complications can develop:
- Electrolyte imbalances - particularly potassium, sodium, calcium, and phosphate 5
- Acid-base disorders - metabolic acidosis 5, 6
- Anemia - due to decreased erythropoietin production 2
- Bone disorders - mineral and bone disorder (MBD) 2
- Cardiovascular disease - increased risk with declining kidney function 3
- Hypertension - both a cause and consequence of kidney disease 7
- Uremia - accumulation of waste products causing symptoms 1
Management by CKD Stage
Stage 1-2 (GFR ≥60 mL/min/1.73 m²)
- Identify and treat underlying cause
- Control blood pressure (target <130/80 mmHg) 2
- Manage cardiovascular risk factors
- Regular monitoring of kidney function
Stage 3 (GFR 30-59 mL/min/1.73 m²)
- Continue above measures
- Monitor for complications (anemia, bone disorders)
- Medication dose adjustments
- Avoid nephrotoxic medications
Stage 4 (GFR 15-29 mL/min/1.73 m²)
- Manage complications actively
- Prepare for kidney replacement therapy
- Medication review and dose adjustments
- Blood pressure management (target 130-139 mmHg systolic) 2
Stage 5 (GFR <15 mL/min/1.73 m²)
- Implement kidney replacement therapy when indicated
- Manage uremic symptoms
- Consider transplant evaluation 2
Important Clinical Considerations
- Terminology: The term "kidney" is preferred over "renal" when describing kidney disease and function 1
- Medication adjustments: Many medications require dose adjustments based on GFR 2
- Nephrotoxic medications: Avoid when possible, especially in advanced CKD 2
- Contrast agents: Use caution with iodinated contrast in patients with kidney disease 1
- Monitoring: Regular assessment of GFR, albuminuria, electrolytes, and acid-base status is essential 2
Prevention Strategies
- Blood pressure control with ACE inhibitors or ARBs for those with albuminuria 2, 8
- Glycemic control in diabetes
- Dietary modifications (reduced dietary acid load) 6
- Avoidance of nephrotoxic medications
- Regular screening for those at high risk
Understanding kidney disease requires recognizing both acute and chronic conditions, their causes, and appropriate management strategies based on disease severity to improve outcomes and quality of life for affected individuals.