Kidney Biopsy of PSGN

Most common histology = diffuse proliferative GN with significant endocapillary proliferation

LM: 

- involvement of all glomeruli

- an influx of neutrophils into the glomerular capillaries 

- proliferation of the capillary endothelial cells

- the capillary lumens are virtually obliterated, reducing the area of ultrafiltration, which leads to a loss of GFR. 

EM: the etiology for the inflammation is seen by the presence of immune complexes in the subepithelial space. The subepithelial deposits are often called "humps because they protrude outward on top of the GBM. 

IF: 

1. The presence of these immune complexes results in a 'granular' appearance by IF using IgG and C3, with additional terminology for this phenomenon being starry sky or garland patterns

2. Additional immune deposits can be noted in the subendothelial space and mesangium. 

It should be noted that a kidney biopsy is usually not done in straightforward cases of PSGN because the treatment will not differ (as noted later). 

A kidney biopsy is recommended only for those atypical cases where the clinical and laboratory features are not compatible with PSGN.