Bilateral fusion of a supernumerary kidney in a cat.

A rare case of bilateral fusion of a supernumerary kidney was found during the necropsy of a female, 8-year-old, mixed breed cat that died as a result of azotemia and chronic enteritis. Apart from enteritis, necropsy revealed four kidneys, two in the sublumbar left region and two in the sublumbar right region, with cortical and medullary regions well individualized and independent; however, the pelvis was partially fused, giving rise to a single ureter. The kidneys were small, whitish and firm, with irregular surfaces. Microscopically, all kidneys displayed normal renal glomeruli and tubules among the immature renal glomeruli and tubules with characteristics of hypoplasia. Foci of glomerulosclerosis, nephrocalcinosis and interstitial fibrosis were also observed.