Persistent metanephric ducts in a geriatric white tiger.

An 18-year-old male intact white Tiger (Panthera tigris) was euthanized after a clinical diagnosis of severe renal failure. Postmortem macroscopic examination of the kidneys revealed unilateral hydronephrosis with renal calculi and bilateral cortical and medullary fibrosis and papillary coagulation necrosis. Interestingly, multiple large persistent metanephric ducts were found at the corticomedullary junctions accompanied by marked interstitial fibrosis, tubular atrophy, and lymphoplasmacytic interstitial nephritis. To our knowledge, this is the first reported case of persistent metanephric ducts in cats.