Post-Streptococcal Glomerulonephritis

Post streptococcal glomerulonephritis is an immune complex glomerulonephritis following infection with nephritogenic strains of group A beta-haemolytic Streptococcus pyogenes.

• It follows pharyngitis (latent period 1 to 3 weeks) or skin infection such as impetigo (3 to 6 weeks); skin-associated disease is common in tropical Africa.
• It affects children aged 5 to 12 years mainly, boys more than girls, and adults in epidemics or with comorbidity (diabetes, alcohol, HIV).
• Nephritogenic strains: M types 1, 4, 12 (pharyngeal), 49, 55, 57 and 60 (skin); crowding, poor hygiene and scabies promote spread.

Abrupt onset of cola-coloured urine, facial puffiness (periorbital oedema), leg oedema, hypertension, oliguria, headache and malaise; fever is usually absent by the onset.

• Subclinical disease (only microscopic haematuria and low complement) is 4 to 10 times more frequent than overt disease.
• Differential diagnosis: IgA nephropathy (synpharyngitic haematuria, no latent period), other post-infectious glomerulonephritis (endocarditis, shunt nephritis), membranoproliferative glomerulonephritis, lupus nephritis, ANCA vasculitis, anti-glomerular basement membrane disease, IgA vasculitis, haemolytic uraemic syndrome, acute tubular necrosis, nephrotic syndrome.
• Complications: hypertensive encephalopathy with seizures, pulmonary oedema and heart failure, hyperkalaemia, acute kidney injury, rapidly progressive glomerulonephritis (adults), persistent proteinuria, chronic kidney disease (in a few, more in adults), nephrotic syndrome.

Urinalysis: haematuria (dysmorphic red cells, red cell casts), proteinuria (usually below nephrotic range), granular and cellular casts; urine protein-to-creatinine ratio.

• Low complement C3 (in 90 percent; returns to normal by 6 to 8 weeks), normal C4.
• Evidence of streptococcal infection: raised antistreptolysin O titre (after pharyngitis), raised anti-DNase B and antihyaluronidase (after skin infection, where antistreptolysin O is often low), positive throat or skin culture.
• Creatinine, urea, electrolytes, albumin, full blood count (normochromic anaemia from haemodilution), chest radiograph if pulmonary oedema, ultrasound.
• Biopsy only if atypical: persistent low complement beyond 12 weeks, rapid decline in function, nephrotic syndrome, persistent hypertension or proteinuria beyond 6 months, and adult onset.

Supportive: bed rest while hypertensive or oedematous, sodium restriction (below 2 g daily), fluid restriction in oliguria (insensible loss plus urine output), protein restriction only in uraemia, daily weight and blood pressure monitoring, and school return once the oedema and hypertension settle.

Pharmacological

• Eradicate streptococci: benzathine penicillin G 1.2 million units IM single dose (600,000 units for children under 27 kg), or phenoxymethylpenicillin 250 to 500 mg four times daily for 10 days (children 125 to 250 mg three to four times daily); allergic patients: erythromycin 250 to 500 mg four times daily for 10 days (children 30 to 50 mg/kg/day in divided doses) or azithromycin 500 mg once daily for 5 days (children 12 mg/kg once daily for 5 days).
• Treat close contacts with positive cultures; treat scabies (permethrin 5 percent cream) and impetigo (topical mupirocin or oral flucloxacillin 250 to 500 mg four times daily).
• Oedema and hypertension: furosemide 1 to 2 mg/kg IV or oral twice daily (adults 40 to 80 mg), amlodipine 0.1 to 0.2 mg/kg daily (adults 5 to 10 mg), nifedipine extended release 0.25 to 0.5 mg/kg twice daily; hypertensive emergency: labetalol 0.2 to 1 mg/kg IV (adults 20 mg bolus) or nicardipine infusion 0.5 to 3 microgram/kg/min; lower blood pressure gradually by 25 percent in the first 8 hours.
• Seizures: diazepam 0.2 to 0.3 mg/kg IV (maximum 10 mg), or lorazepam 0.1 mg/kg.
• Hyperkalaemia: calcium gluconate 10 percent 0.5 mL/kg IV, salbutamol, insulin with glucose.
• Corticosteroids and immunosuppressants are not indicated except in crescentic disease (methylprednisolone 500 to 1000 mg IV daily for 3 days then prednisolone 1 mg/kg daily with cyclophosphamide).

Procedures: dialysis for refractory fluid overload, hyperkalaemia, uraemia; renal biopsy when the cause is unclear.

Special groups: children (excellent prognosis, over 95 percent recover), adults and diabetics (persistent proteinuria and renal impairment in up to 30 percent), pregnancy (specialist care).

Red flags: seizures or encephalopathy, creatinine rising beyond 1 week, anuria, nephrotic syndrome, persistently low C3 beyond 12 weeks, haemoptysis.

Follow-up: blood pressure, weight and urinalysis weekly then monthly; haematuria may persist 1 to 2 years and proteinuria 6 months; complement at 8 to 12 weeks; annual review (blood pressure, urine protein, creatinine) for 3 to 5 years; recurrence is rare.