Outbreaks of renal failure associated with melamine and cyanuric acid in dogs and cats in 2004 and 2007

Sixteen animals affected in 2 outbreaks of pet food-associated renal failure (2 dogs in 2004; 10 cats and 4 dogs in 2007) were evaluated for histopathologic, toxicologic, and clinicopathologic changes. All 16 animals bad clinical and laboratory evidence of uremia, including anorexia, vomiting, lethargy, polyuria, azotemia, and hyperphosphatemia. Where measured, serum hepatic enzyme concentrations were normal in animals from both outbreaks. All animals died or were euthanized because of severe uremia. Distal tubular lesions were present in all 16 animals, and unique polarizable crystals with striations were present in distal tubules or collecting ducts in all animals. The proximal tubules were largely unaffected. Crystals and histologic appearance were identical in both outbreaks. A chronic pattern of histologic change, characterized by interstitial fibrosis and inflammation, was observed in some affected animals. Melamine and cyanuric acid were present in renal tissue from both outbreaks. These results indicate that the pet food-associated renal failure outbreaks in 2004 and 2007 share identical clinical, histologic, and toxicologic findings, providing compelling evidence that they share the same causation.