Glomerular basement membrane discontinuities. Scanning electron microscopic study of acellular glomeruli.

Glomerulonephritides which develop necrotizing and crescentic lesions usually have glomerular basement membrane (GBM) disruptions when carefully examined by light microscopy or transmission electron microscopy. Despite numerous excellent and detailed ultrastructural investigations of GBM discontinuities, a complete appreciation of their actual number, appearance, and distribution within a glomerulus has been difficult to achieve by reconstruction of two-dimensional light or transmission electron microscopic images. Selective removal of podocytes by a sequence of lytic and solubilization procedures has been developed which exposes any structural alteration of the GBM to direct examination by scanning electron microscopy. A case of idiopathic, immune-complex-negative, focal-segmental necrotizing glomerulonephritis has been studied by this technique, permitting three-dimensional visualization of the GBM defects which result in free communication between the vascular and urinary spaces. These disruptions were distinctive by their frequency within an affected lobule, variable size, and sharply demarcated edges. Application of this technique to human renal biopsies is capable of enhancing our understanding of the morphologic alterations occurring in human glomerulonephritis.