Lactate as a diagnostic test for septic peritoneal effusions in dogs and cats.

Lactate concentration in peritoneal fluid was evaluated and compared to blood lactate concentration in dogs and cats with septic and nonseptic abdominal effusions. All dogs with septic effusions had a peritoneal fluid lactate concentration >2.5 mmol/L and a peritoneal fluid lactate concentration higher than blood lactate, resulting in a negative blood to fluid lactate difference. In dogs, the diagnostic accuracy of the peritoneal fluid lactate concentration and the blood to fluid lactate difference in differentiating septic peritoneal effusion was 95% and 90%, respectively. Peritoneal fluid lactate concentration and blood to fluid lactate difference were not accurate tests for detecting septic peritoneal effusions in cats.