Kidney biopsy findings in poststreptococcal glomerulonephritis
What does the kidney biopsy show in poststreptococcal glomerulonephritis?
The most common histology seen with all forms of poststreptococcal glomerulonephritis is diffuse proliferative glomerulonephritis with significant endocapillary proliferation.
By light microscopy, this lesion is characterized by involvement of almost all glomeruli, with an influx of neutrophils into the glomerular capillaries and a proliferation of the capillary endothelial cells.
The capillary lumens are virtually obliterated, reducing the area for ultrafiltration, which leads to a loss of glomerular filtration rate (GFR). By electron microscopy, 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 basement membrane. The presence of these immune complexes results in a “granular” appearance by immunofluorescence using IgG and C3, with additional terminology for this phenomenon being “starry sky” or “garland” patterns.
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 poststreptococcal glomerulonephritis 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 poststreptococcal glomerulonephritis.
