Key diagnostic features of selected diseases in renal biopsy are illustrated, with light, immunofluorescence, and electron microscopic images. Common urinalysis findings are also documented.
Minimal-change disease. In minimal-change disease, light microscopy is unremarkable (A), whereas electron microscopy (B) reveals podocyte injury evidenced by complete foot process effacement. (ABF/Vanderbilt Collection.)
Focal segmental glomerulosclerosis (FSGS). There is a well-defined segmental increase in matrix and obliteration of capillary loops (arrow), the sine qua non of segmental sclerosis not otherwise specified (NOS) type. (EGN/UPenn Collection.)
Collapsing glomerulopathy. There is segmental collapse (arrow) of the glomerular capillary loops and overlying podocyte hyperplasia. This lesion may be idiopathic or associated with HIV infection and has a particularly poor prognosis. (ABF/Vanderbilt Collection.)
Hilar variant of FSGS. There is segmental sclerosis of the glomerular tuft at the vascular pole with associated hyalinosis, also present in the afferent arteriole (arrows). This lesion often occurs as a secondary response when nephron mass is lost due to, e.g., scarring from other conditions. Patients usually have less proteinuria and less steroid response than FSGS, NOS type. (ABF/Vanderbilt Collection.)
Tip lesion variant of FSGS. There is segmental sclerosis of the glomerular capillary loops at the proximal tubular outlet (arrow). This lesion has a better prognosis than other types of FSGS. (ABF/Vanderbilt Collection.)
Postinfectious (poststreptococcal) glomerulonephritis. The glomerular tuft shows proliferative changes with numerous polymorphonuclear leukocytes (PMNs), with a crescentic reaction (arrow) in severe cases (A). These deposits localize in the mesangium and along the capillary wall in a subepithelial pattern and stain dominantly for C3 and to a lesser extent for IgG (B). Subepithelial hump-shaped deposits are seen by electron microscopy (arrow) (C). (ABF/Vanderbilt Collection.)
Membranous glomerulopathy. Membranous glomerulopathy is due to subepithelial deposits, with resulting basement membrane reaction, resulting in the appearance of spike-like projections on silver stain (A). The deposits are directly visualized by fluorescent anti-IgG, revealing diffuse granular capillary loop staining (B). By electron microscopy, the subepithelial location of the deposits ...
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