*Postinfectious Glomerulonephritis

Definition, Etiology, PathogenesisTop

Postinfectious glomerulonephritis (PIGN) is a rapidly developing glomerular disease with circulating immune complexes associated with an ongoing or a recent infection. Classically, it is related to streptococcal infections, although it develops also with staphylococcal infections, especially in elderly patients. PIGN is less commonly linked to other bacterial and viral pathogens.

Clinical FeaturesTop

PIGN previously affected mostly children, and it is still more common in this group in the developing countries. However, the incidence has decreased in the developed world, likely reflecting the quicker and more widespread use of antibiotics, such that PIGN is now significantly more common in adults and preferentially affects the elderly as well as patients with diabetes mellitus or alcoholism.

The disease develops acutely, usually 1 to 2 weeks after streptococcal pharyngitis or 2 to 3 weeks after streptococcal skin infections. PIGN due to staphylococcal infections is slightly more delayed, occurring approximately after 4 weeks.

The usual presentation is nephritic syndrome, with most patients having edema (85% of individuals), hypertension (60%-80%), and abnormal urinalysis/microscopy results (microscopic hematuria and red blood cell casts). Proteinuria is usually not in the nephrotic range. Systemic symptoms include malaise, loss of appetite, nausea, and vomiting. While acute kidney injury (AKI) usually exists, it does not commonly progress to the need for renal replacement. PIGN can present as both nephrotic syndrome and rapidly progressive glomerulonephritis (RPGN), although both are rare. Patients can also be asymptomatic; such cases are estimated to be 4 to 5 times more common than symptomatic ones.

DiagnosisTop

1. Urinalysis/microscopy: Non–nephrotic range proteinuria and active urine sediment.

2. Blood tests: Increased antistreptolysin O (ASO) titers are observed in 90% of patients after streptococcal throat infections and in up to 80% of patients after streptococcal skin infections. Hypergammaglobulinemia along with low serum hemolytic complement activity, low C3 levels, and normal C4 levels are often present.

3. Kidney biopsy: Biopsy is not usually done and only considered in patients who do not recover renal function or have an abnormal presentation.

TreatmentTop

Treatment of active infection with antibiotics is necessary if infection is present, but given the delay between infection and renal disease, the infection has often already resolved or been treated. Treatment of nephritic syndrome includes sodium and fluid restriction and loop diuretics as necessary. Hypertension should be controlled. Renin-angiotensin system blockers should be used with caution in the setting of AKI. Glucocorticoids can be considered in the setting of PIGN presenting as RPGN, although observational data suggest that they do not change outcomes.Evidence 1Weak recommendation (benefits likely outweigh downsides, but the balance is close or uncertain; an alternative course of action may be better for some patients). Low Quality of Evidence (low confidence that we know true effects of the intervention). Quality of Evidence lowered due to the observational nature of data. Nasr SH, Markowitz GS, Stokes MB, Said SM, Valeri AM, D'Agati VD. Acute postinfectious glomerulonephritis in the modern era: experience with 86 adults and review of the literature. Medicine (Baltimore). 2008 Jan;87(1):21-32. doi: 10.1097/md.0b013e318161b0fc. PubMed PMID: 18204367.

PrognosisTop

The vast majority of children have complete recovery of their renal function, whereas up to 70% of adults will develop chronic kidney disease, with patients with diabetes being at greater risk of this complication. Recurrences of PIGN are rare.