Chronic kidney disease

Chronic kidney disease (CKD) is a long-term condition characterized by a gradual and irreversible loss of kidney function over months or years. The kidneys normally filter waste products, excess fluids, and electrolytes from the blood, maintaining internal balance and contributing to essential processes such as blood pressure regulation, red blood cell production, and bone health. In CKD, these functions progressively deteriorate, leading to the accumulation of toxins and imbalances in the body. CKD is a major global health issue, closely associated with cardiovascular disease, diabetes, and hypertension, and significantly increases the risk of morbidity and mortality.

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Causes and Risk Factors

The most common causes of CKD are:

• Diabetes mellitus (type 1 and type 2): Chronic hyperglycemia damages the glomeruli, causing diabetic nephropathy.

• Hypertension: Persistently high blood pressure injures the renal vasculature, reducing filtration capacity.

• Glomerulonephritis: Inflammatory disorders directly affecting the glomeruli.

• Polycystic kidney disease: A genetic condition leading to cyst formation and progressive renal impairment.

• Chronic urinary tract obstruction: From stones, enlarged prostate, or strictures.

• Repeated kidney infections: Recurrent pyelonephritis can scar and damage renal tissue.

• Autoimmune diseases: Conditions such as lupus nephritis.

Risk factors include older age, family history of kidney disease, cardiovascular disease, obesity, smoking, and prolonged use of nephrotoxic drugs (e.g., NSAIDs, aminoglycosides).

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Stages of CKD

CKD is classified into five stages according to the estimated glomerular filtration rate (eGFR):

• Stage 1: eGFR ≥ 90 mL/min/1.73 m² with evidence of kidney damage (proteinuria, structural abnormalities).

• Stage 2: eGFR 60–89 mL/min/1.73 m² with evidence of kidney damage.

• Stage 3a: eGFR 45–59 mL/min/1.73 m².

• Stage 3b: eGFR 30–44 mL/min/1.73 m².

• Stage 4: eGFR 15–29 mL/min/1.73 m².

• Stage 5 (end-stage renal disease): eGFR < 15 mL/min/1.73 m², requiring dialysis or transplantation.

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Symptoms

CKD often progresses silently in its early stages. Symptoms become apparent as kidney function declines:

• Fatigue and weakness

• Nausea, vomiting, and loss of appetite

• Itching and dry skin

• Swelling in ankles, feet, or hands due to fluid retention

• Shortness of breath

• Increased or decreased urination

• Muscle cramps and restless legs

• Confusion or difficulty concentrating

• High blood pressure that is difficult to control

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Complications

CKD leads to several systemic complications, including:

• Cardiovascular disease: Major cause of death in CKD patients due to hypertension, dyslipidemia, and vascular calcification.

• Anemia: Reduced erythropoietin production.

• Mineral and bone disorders: Disturbed calcium, phosphate, and vitamin D metabolism, leading to renal osteodystrophy.

• Electrolyte imbalances: Hyperkalemia, metabolic acidosis, and sodium retention.

• Fluid overload: Pulmonary edema and hypertension.

• Malnutrition and muscle wasting.

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Diagnosis

Diagnosis involves clinical evaluation, laboratory investigations, and imaging:

• Blood tests: Serum creatinine, urea, electrolytes, and eGFR calculation.

• Urinalysis: Proteinuria, albumin-to-creatinine ratio (ACR), hematuria.

• Imaging: Ultrasound to assess kidney size and structure.

• Kidney biopsy: To determine underlying pathology, especially in glomerular diseases.

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Management

There is no cure for CKD, but treatment aims to slow progression, manage symptoms, and prevent complications.

Lifestyle Modifications

• Dietary management: Low-salt, moderate-protein diet, control of potassium and phosphate intake.

• Weight control and exercise.

• Smoking cessation.

• Alcohol moderation.

Pharmacological Treatment

1. Control of underlying conditions:

   • Diabetes: Metformin (500–2000 mg daily, dose adjustment in advanced CKD), insulin therapy where needed.

   • Hypertension:

     • First-line: ACE inhibitors (e.g., enalapril 5–20 mg/day) or ARBs (e.g., losartan 50–100 mg/day) to reduce proteinuria and protect renal function.

     • Additional agents: Calcium channel blockers (e.g., amlodipine 5–10 mg/day), beta-blockers (e.g., bisoprolol 5–10 mg/day), diuretics (e.g., furosemide 20–80 mg/day, thiazides in earlier stages).

2. Anemia management:

   • Erythropoiesis-stimulating agents (e.g., epoetin alfa 50–150 units/kg/week).

   • Iron supplementation: Oral ferrous sulfate (200 mg two to three times daily) or IV iron preparations if oral forms are not tolerated.

3. Bone and mineral disorders:

   • Phosphate binders: calcium acetate 667 mg with meals or non-calcium binders (e.g., sevelamer 800–1600 mg with meals).

   • Vitamin D analogs: calcitriol 0.25–1 mcg daily.

   • Calcimimetics: cinacalcet 30–180 mg/day for secondary hyperparathyroidism.

4. Hyperkalemia management:

   • Restrict dietary potassium.

   • Potassium binders: sodium zirconium cyclosilicate 10 g daily or patiromer 8.4 g daily.

   • Emergency treatment (in acute settings): IV calcium gluconate, insulin with glucose, salbutamol nebulization.

5. Metabolic acidosis:

   • Sodium bicarbonate (650 mg two to three times daily).

Renal Replacement Therapy

• Dialysis: Hemodialysis or peritoneal dialysis for stage 5 CKD.

• Kidney transplantation: The definitive treatment for ESRD.

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Prevention and Monitoring

• Regular screening for high-risk populations (diabetics, hypertensives).

• Monitoring eGFR and proteinuria progression.

• Early referral to nephrology for advanced CKD.

• Patient education on medication adherence and lifestyle adjustments.

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Prognosis

CKD is progressive and associated with significant morbidity. Prognosis depends on underlying cause, control of comorbidities, and timely initiation of appropriate treatment. Early detection and intervention are crucial in delaying progression to end-stage renal disease.