Acute Glomerulonephritis

Acute glomerulonephritis is inflammation of the glomeruli causing an acute nephritic syndrome: haematuria, hypertension, oedema, proteinuria and a fall in glomerular filtration rate.

• Infection-related: post-streptococcal, staphylococcal, endocarditis, shunt nephritis, hepatitis B and C, HIV, malaria (quartan), schistosomiasis, syphilis.
• Immune-mediated: IgA nephropathy, IgA vasculitis, lupus nephritis, ANCA vasculitis (granulomatosis with polyangiitis, microscopic polyangiitis), anti-glomerular basement membrane disease, membranoproliferative glomerulonephritis, cryoglobulinaemia.
• Rapidly progressive disease (crescentic) loses over half of nephrons within weeks to months.

Cola-coloured or red urine, periorbital and leg oedema, hypertension, oliguria, headache, malaise.

• Associated: sore throat or skin infection 1 to 6 weeks earlier (post-streptococcal), purpura and abdominal pain (IgA vasculitis), haemoptysis (anti-glomerular basement membrane disease, vasculitis), rash, arthritis, fever (lupus, vasculitis), cardiac murmur (endocarditis).
• Differential diagnosis: nephrotic syndrome, acute interstitial nephritis, acute tubular necrosis, urinary tract infection, stones, tumour, thrombotic microangiopathy, polycystic kidney, myoglobinuria.
• Complications: hypertensive encephalopathy, pulmonary oedema and heart failure, hyperkalaemia, acute kidney injury, rapidly progressive glomerulonephritis, nephrotic syndrome, chronic kidney disease and end stage kidney disease.

Urinalysis: haematuria with dysmorphic red cells and red cell casts, proteinuria; urine protein-to-creatinine ratio.

• Creatinine, urea, electrolytes, bicarbonate, albumin, full blood count, ESR, C-reactive protein.
• Complement C3 and C4: low C3 in post-infectious, lupus, membranoproliferative and shunt nephritis; normal in IgA nephropathy, vasculitis and anti-glomerular basement membrane disease.
• Serology: antistreptolysin O and anti-DNase B, throat or skin swab, blood cultures, ANA and anti-double stranded DNA, ANCA (proteinase 3 and myeloperoxidase), anti-glomerular basement membrane antibody, hepatitis B and C, HIV, cryoglobulins, serum electrophoresis.
• Renal ultrasound; chest radiograph; biopsy for rapidly progressive disease, unexplained or severe course, low C3 beyond 12 weeks, nephrotic range proteinuria, or non-recovery in 2 to 3 weeks.

Supportive

• Sodium restriction (below 2 g daily), fluid restriction to previous day's urine output plus 500 mL (insensible loss), daily weights, blood pressure monitoring, bed rest in the acute phase.
• Restrict potassium and protein (0.8 g/kg/day) when oliguric.

Pharmacological

• Hypertension and fluid overload: furosemide 40 to 80 mg IV or orally twice daily (children 1 to 2 mg/kg); amlodipine 5 to 10 mg daily or nifedipine extended release 30 to 60 mg daily; labetalol 20 mg IV bolus then 20 to 80 mg every 10 minutes (maximum 300 mg) for hypertensive emergency; avoid ACE inhibitors and angiotensin receptor blockers until creatinine and potassium are stable.
• Infection: eradicate active infection (penicillin V 500 mg four times daily for 10 days, or benzathine penicillin G 1.2 million units IM single dose; endocarditis with prolonged IV therapy).
• Specific immunosuppression by cause: ANCA vasculitis and severe lupus nephritis (methylprednisolone 500 to 1000 mg IV daily for 3 days, prednisolone 1 mg/kg daily, cyclophosphamide 15 mg/kg IV every 2 to 3 weeks or rituximab 375 mg/m2 weekly for 4; mycophenolate mofetil 1 g twice daily for lupus); anti-glomerular basement membrane disease (plasma exchange 4 L daily for 14 days, prednisolone and cyclophosphamide); IgA nephropathy with crescents (corticosteroids).
• Hyperkalaemia: calcium gluconate, insulin with glucose, salbutamol, binders.

Procedures: dialysis for refractory hyperkalaemia, pulmonary oedema, uraemia; plasma exchange where indicated; kidney biopsy.

Special groups: children (usually self-limited post-streptococcal disease), pregnancy (nephrology and obstetric care; avoid cyclophosphamide), elderly (consider vasculitis and endocarditis).

Red flags: seizures or confusion, creatinine doubling, oliguria, haemoptysis, pulmonary oedema, potassium above 6.5 mmol/L.

Follow-up: weekly blood pressure, creatinine, urinalysis and weight until stable; complement at 8 to 12 weeks; persistent proteinuria or low complement merits biopsy; yearly review for chronic kidney disease.