Primary renal diseases of the cat

Membranoproliferative glomerulonephritis in a young cat

A 9-month-old male Japanese domestic cat showed pleural effusion, ascites, azotemia, hypoproteinemia and severe proteinuria. Histopathology of the percutaneous renal biopsy specimen revealed that all glomeruli showed intense mesangial hypercellularity with an increased mesangial matrix and thickening of the capillary walls, resulting in lobular accentuation of the glomerular tufts. Frequent duplication of the capillary walls was also observed. Immunostaining for alpha-smooth muscle actin distinctly revealed mesangial interposition. Diffuse global and linear deposition of C3 and IgG was observed mostly along the peripheral capillary loops. Electron microscopy confirmed frequent circumferential mesangial interposition and subendothelial dense-deposits in the glomerulus. The glomerular lesion was consistent with human membranoproliferative glomerulonephritis type I, and might be a rare case that developed at young age.

Glomerulosclerosis in captive cheetahs (Acinonyx jubatus)

The cheetah (Acinonyx jubatus) is an endangered species with low fecundity and premature death in captivity. A previous survey determined that renal failure as a result of glomerulosclerosis was a major cause of death in captive populations. This study characterizes the morphologic, histochemical, and epidemiologic properties of glomerulosclerosis in this population. Kidneys from 87 cheetahs were examined by light microscopy; kidneys from six of those cheetahs were examined by electron and fluorescent microscopy using special stains specific for collagen, glycoproteins, reticulin, and fibrin. Immunohistochemistry for the advanced glycosylation end products (AGEs), pyrraline and pentosidine, also was performed on these cases. Glomerulosclerosis was present to some degree in 82% of the population, and in 30% of cheetahs the sclerosis was moderate to severe. Affected cheetah kidneys had thickened glomerular and tubular basement membranes, culminating in glomerulosclerosis. Thickened basement membranes were positive for collagen, glycoproteins, reticulin, and AGEs. Ultrastructurally, membrane material was homogeneous and fibrillar without electron-dense deposits. This glomerular lesion in cheetahs resembles diabetic glomerulopathy in humans and chronic progressive nephropathy in rats. No cheetahs had lesions of diabetes. However, adrenal cortical hyperplasia was prevalent and highly correlated with glomerulosclerosis in this population. If cheetahs with glomerulosclerosis had hypercorticoidism, then hyperglycemia and glomerular hypertension could lead to progressive AGE and plasma protein accumulations in membrane lesions. As in rats, daily feeding of high-protein diets and lack of genetic variation in the population may further contribute to the high prevalence of glomerulosclerosis in captive cheetahs.