Hyperammonaemia in cats

Ammonia is an important nitrogen source required for amino acid, protein and nucleic acid synthesis. In addition, it plays an essential role in the kidney's maintenance of acid–base balance. However, high concentrations of ammonia are cytotoxic and clinical signs primarily reflect neurotoxicity. The body detoxifies ammonia through the urea cycle in the liver or by consuming ammonia in the conversion of glutamate to glutamine in the liver, brain and muscle tissue. The most common cause of hyperammonaemia in cats is congenital portosystemic shunting. Additional causes include cobalamin or arginine deficiency, disruption of the urea cycle by congenital enzyme deficiencies or acute liver failure, excessive muscle activity, infections with urease-producing bacteria, kidney disease and multiple acquired portosystemic shunts.