Naturally occurring canine glomerulonephritis.

The 8 dogs with glomerulonephritis in this study had progressive renal disease characterized by proteinuria, azotemia and hypoalbuminemia, without peripheral edema and ascites. Observed by light, fluorescence and electron microscopy, the glomeruli were diffusely but irregularly involved. By light microscopy, there was focal mesangial proliferation, and the peripheral portions of many glomerular capillary loops were thickened by eosinophilic material along the endothelial sides of basement membranes. Immunofluorescence studies demonstrated granular deposits of IgG and beta1C-globulin outlining glomerular basement membranes and within the mesangium. Ultrastructurally, there were electron-dense deposits in the mesangium and within the endothelial side of glomerular basement membranes. Subepithelial deposits were never seen. The majority of clinical and morphologic features suggested a glomerulonephritis of immune-complex type. However, the unique aspects of the ultrastructural lesion precluded this assumption based solely on morphologic criteria.