Pathogenesis of Acute PSGN
- Triggering Infection: Occurs 1-3 weeks post-infection with Group A Beta-Hemolytic Streptococcus (GABHS), commonly affecting the throat (pharyngitis) or skin (impetigo).
- Immune Response:
- Formation of immune complexes (streptococcal antigens, antibodies, and complement).
- Deposition in glomerular basement membrane and mesangium.
- Activation of complement and inflammatory cascade leading to glomerular injury.
Result: Glomerular hypercellularity, endothelial swelling, and capillary lumen narrowing impair filtration.
Clinical Features of Acute PSGN
Classic Triad:
- Hematuria: Gross (cola-colored urine) or microscopic.
- Edema: Periorbital and dependent edema.
- Hypertension: Due to fluid overload and renin-angiotensin activation.
Other Features:
- Oliguria or reduced urine output.
- Proteinuria (non-nephrotic range).
- Symptoms of preceding streptococcal infection (e.g., sore throat, skin lesions).
Lab Findings:
- Elevated antistreptolysin-O (ASO) titers.
- Low complement levels (C3, normal C4).
- Urinalysis: Dysmorphic RBCs, RBC casts, and mild proteinuria.
Management of Acute PSGN
Supportive Care:
- Fluid and Sodium Restriction: To control edema and hypertension.
- Diuretics (e.g., Furosemide): For fluid overload and hypertension.
Infection Control:
- Complete the course of antibiotics for the underlying streptococcal infection (e.g., Penicillin).
Hypertension Control:
- Antihypertensives (e.g., Calcium channel blockers like Amlodipine or ACE inhibitors if no contraindication).
Monitoring:
- Regular renal function tests (serum creatinine, electrolytes).
- Blood pressure monitoring.
Complications of Acute PSGN
Acute Complications:
- Hypertensive Encephalopathy: Severe hypertension causing seizures, headache, and altered mental status.
- Heart Failure: Volume overload leading to pulmonary edema.
- Acute Kidney Injury (AKI): Transient but severe impairment of renal function.
- Electrolyte Imbalance: Hyperkalemia and metabolic acidosis.
- Infections: Due to reduced immunity and secondary infections.
Chronic Complications:
- Chronic kidney disease (CKD) in rare cases due to prolonged glomerular injury.
Management of Complications
Hypertensive Crisis:
- IV antihypertensives (e.g., Labetalol, Nitroprusside).
- Close monitoring in ICU settings.
Heart Failure:
- IV diuretics (e.g., Furosemide).
- Oxygen supplementation or mechanical ventilation if necessary.
Acute Kidney Injury:
- Supportive therapy (dialysis if indicated for severe fluid overload or refractory hyperkalemia).
- Correct acidosis and electrolyte imbalances.
Prevention of Progression to CKD:
- Long-term follow-up with a nephrologist.
- Control of proteinuria and hypertension.
