Chronic Kidney Disease for PA
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Chronic Kidney Disease (CKD) for the Physician Assistant Licensing Exam
Definition
- Chronic Kidney Disease (CKD): Progressive and irreversible decline in kidney function lasting for at least 3 months. It is characterized by either decreased glomerular filtration rate (GFR) or evidence of kidney damage such as proteinuria, hematuria, or abnormal imaging.
- Diagnosis:
- GFR <60 mL/min/1.73 m² for ≥3 months, or
- Evidence of kidney damage (e.g., albuminuria ≥30 mg/g, abnormal urinalysis, or imaging findings) for ≥3 months.
Staging (KDIGO Classification)
- Stage 1: GFR ≥90 mL/min/1.73 m² with evidence of kidney damage.
- Stage 2: GFR 60–89 mL/min/1.73 m² with evidence of kidney damage.
- Stage 3: GFR 30–59 mL/min/1.73 m².
- Stage 4: GFR 15–29 mL/min/1.73 m².
- Stage 5: GFR <15 mL/min/1.73 m² (end-stage renal disease, ESRD).
Etiology
- Diabetes Mellitus (DM): Chronic hyperglycemia leads to glomerular hyperfiltration and nephron loss, making diabetes the most common cause of CKD.
- Hypertension: Chronic uncontrolled hypertension causes nephrosclerosis and ischemic injury, leading to progressive nephron loss.
- Glomerulonephritis: Inflammatory diseases of the glomeruli, such as IgA nephropathy or lupus nephritis, can cause irreversible kidney damage.
- Polycystic Kidney Disease (PKD): A genetic condition leading to progressive renal cyst formation and destruction of normal kidney tissue.
- Other Causes:
- Recurrent urinary tract infections or chronic pyelonephritis.
- Obstructive uropathy (e.g., kidney stones or benign prostatic hyperplasia).
- Chronic use of nephrotoxic drugs (e.g., NSAIDs).
Pathophysiology
- Hyperfiltration Injury: Initial nephron loss (e.g., from DM or hypertension) triggers compensatory hyperfiltration in remaining nephrons, leading to increased glomerular pressure, glomerulosclerosis, and further nephron damage.
- Glomerulosclerosis: Irreversible scarring of the glomeruli, leading to a gradual decline in GFR.
- Tubulointerstitial Fibrosis: Chronic inflammation leads to tubular atrophy and fibrosis of the interstitium, further reducing renal function.
- Uremia: As GFR decreases, uremic toxins accumulate, leading to systemic symptoms like fatigue, nausea, and cognitive dysfunction.
Clinical Presentation
- Early Stages (1–3):
- Often asymptomatic, with findings like proteinuria or hypertension as the first signs.
- Edema from impaired sodium excretion.
- Late Stages (4–5):
- Uremia: Symptoms include fatigue, anorexia, pruritus, muscle cramps, and cognitive impairment.
- Hypertension: Due to sodium retention and activation of the renin-angiotensin-aldosterone system (RAAS).
- Anemia: Decreased erythropoietin production.
- Bone Disease: Renal osteodystrophy from altered calcium-phosphate metabolism.
- Fluid Overload: Dyspnea, pulmonary edema, and peripheral edema.
Diagnostic Evaluation
- Serum Creatinine and GFR: Monitor disease progression.
- Urinalysis:
- Proteinuria: Indicates kidney damage, typically measured as the albumin-to-creatinine ratio (UACR).
- Hematuria: Suggests underlying glomerular disease (e.g., glomerulonephritis).
- Electrolytes: Hyperkalemia, hyperphosphatemia, and hypocalcemia in advanced disease.
- Imaging:
- Renal Ultrasound: Often shows small, shrunken kidneys in advanced CKD, or polycystic kidneys in PKD.
Management
- Control of Underlying Causes:
- Diabetes: Tight glycemic control (HbA1c <7%) to reduce progression.
- Hypertension: Use of ACE inhibitors or ARBs to reduce proteinuria and slow disease progression, targeting a blood pressure <130/80 mmHg.
- Dietary Management:
- Protein Restriction: To reduce uremic symptoms and slow progression (0.8 g/kg/day).
- Sodium Restriction: To manage hypertension and prevent fluid overload.
- Phosphorus Restriction: To manage hyperphosphatemia and prevent bone disease.
- Complication Management:
- Anemia: Erythropoiesis-stimulating agents (ESAs) and iron supplementation.
- Hyperkalemia: Dietary restriction, loop diuretics, or potassium binders.
- Bone Disease: Phosphate binders, vitamin D analogs, and calcimimetics.
- End-Stage Renal Disease (ESRD):
- Dialysis: For patients with GFR <15 mL/min/1.73 m² and symptoms of uremia or complications such as hyperkalemia.
- Kidney Transplantation: The definitive treatment for ESRD, providing the best long-term outcomes.
Complications
- Cardiovascular Disease: The leading cause of death in CKD patients, primarily due to hypertension and dyslipidemia.
- Electrolyte Imbalances: Hyperkalemia, hyperphosphatemia, and metabolic acidosis can lead to life-threatening complications.
- Renal Osteodystrophy: Secondary hyperparathyroidism leads to bone resorption and increased fracture risk.
Key Points
- CKD is a progressive decline in kidney function over at least 3 months, diagnosed by reduced GFR or evidence of kidney damage such as albuminuria.
- Common causes include diabetes, hypertension, and glomerulonephritis.
- Management focuses on controlling underlying diseases, dietary modifications, and managing complications like anemia, hyperkalemia, and bone disease.
- End-stage renal disease (ESRD) requires dialysis or kidney transplantation.
- Cardiovascular disease is the leading cause of mortality in CKD patients, highlighting the importance of early intervention and risk factor modification.