Acute Post Streptococcal Glomerulonephritis

Acute post streptococcal glomerulonephritis is an immune mediated nephritic syndrome occurring after infection with nephritogenic strains of group A Streptococcus. It typically develops approximately 1 to 3 weeks after streptococcal pharyngitis or 3 to 6 weeks after streptococcal skin infection.

Immune complex deposition activates complement and produces glomerular inflammation, resulting in haematuria, reduced glomerular filtration, sodium retention and hypertension.

Most children recover completely.

The classical presentation is an acute nephritic syndrome:

• Cola, tea or smoky coloured urine from macroscopic haematuria
• Periorbital oedema, particularly in the morning
• Peripheral oedema
• Reduced urine output
• Hypertension
• Headache
• Nausea or vomiting

Severe complications include pulmonary oedema, hypertensive encephalopathy, hyperkalaemia and acute kidney injury.

Urinalysis typically shows:

• Haematuria
• Proteinuria, usually subnephrotic
• Red cell casts

Blood investigations:

• Urea, creatinine and electrolytes
• Low C3, which usually normalizes within approximately 6 to 8 weeks
• C4 is usually normal
• ASO titre supports preceding streptococcal pharyngitis
• Anti DNase B is particularly useful after skin infection

Persistent complement depression beyond approximately 8 to 12 weeks should prompt reconsideration of the diagnosis.

Treatment is primarily supportive.

• Restrict sodium in oedema and hypertension.

• Restrict fluids if significant oedema, oliguria or fluid overload is present.

• For clinically important oedema or pulmonary congestion, furosemide 1 mg/kg IV or PO, repeated or adjusted according to response.

• Treat significant hypertension. Oral agents such as amlodipine may be used in stable hypertension. Hypertensive emergency requires controlled IV therapy and close monitoring.

• Antibiotics do not reverse established glomerulonephritis but eradicate residual streptococcal infection and reduce transmission. If active streptococcal infection remains, give an appropriate penicillin regimen.

Dialysis may be required for refractory pulmonary oedema, severe hyperkalaemia, severe acidosis or progressive uraemia.