Post-streptococcal Glomerulonephritis
A 63-year-old woman presents with cola-coloured urine and facial puffiness. Two weeks earlier she had a sore throat treated with penicillin V. Blood pressure is 150/94 mm Hg, with periorbital oedema and pitting ankle oedema. Urinalysis shows 3+ blood and 2+ protein with red cell casts. C3 is low and the antistreptolysin O titre is elevated. Which of the following is the most appropriate treatment at this time?
- A.Hydrochlorothiazide
- B.Prednisolone
- C.FurosemideCorrect
- D.Cyclophosphamide
Explanation
This is post-streptococcal glomerulonephritis, an immune complex nephritic syndrome occurring 1 to 3 weeks after streptococcal pharyngitis or 3 to 6 weeks after skin infection, and treatment is entirely supportive with salt and water restriction plus a loop diuretic. Deposition of immune complexes in the glomerular capillary wall activates complement, consuming C3 while sparing C4, and causes an inflammatory proliferative lesion that reduces glomerular filtration; the resulting sodium and water retention produces volume-dependent hypertension, oedema and mild azotaemia. Furosemide directly reverses this volume expansion, lowering blood pressure and relieving periorbital and peripheral oedema more effectively and more quickly than any other measure, and it remains effective when the glomerular filtration rate is reduced. Hydrochlorothiazide is a much weaker natriuretic and loses efficacy once creatinine clearance falls below about 30 mL/min, so it is not the agent of choice in acute nephritic syndrome. Corticosteroids and cytotoxic agents such as cyclophosphamide have no role in uncomplicated post-streptococcal disease, which is self-limiting with more than 95% recovery in children and a good though slightly less certain outcome in adults; they are reserved for rapidly progressive glomerulonephritis with crescents on biopsy. Antibiotics eradicate the organism and limit spread but do not alter the course of established nephritis, and this patient has already been treated. C3 should normalise within 8 weeks, and persistent hypocomplementaemia should prompt reconsideration of membranoproliferative glomerulonephritis or lupus nephritis.
Why each option
- A.
- Thiazides are weak natriuretics and become ineffective as glomerular filtration declines.
- B.
- Corticosteroids do not improve outcomes in uncomplicated post-streptococcal glomerulonephritis and are reserved for crescentic disease.
- C.
- Correct. A loop diuretic treats the volume overload that drives the hypertension and oedema of acute nephritic syndrome.
- D.
- Cyclophosphamide is an immunosuppressant for rapidly progressive or vasculitic glomerulonephritis, not for this self-limiting condition.
Reference: KDIGO 2021 Clinical Practice Guideline for the Management of Glomerular Diseases
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