Etiology and effusion characteristics in 29 cats and 60 dogs with pyothorax (2010‐2020)

Abstract

Background: Pyothorax, an accumulation of inflammatory fluid in the pleural space, is often caused by foreign body inhalation in dogs, whereas the etiology in cats can be more difficult to discern.Objective: Compare clinical, microbiologic findings, and etiology in cats and dogs with pyothorax.Animals: Twenty-nine cats and 60 dogs.Methods: Medical records of cats and dogs diagnosed with pyothorax from 2010 to 2020 were reviewed. Clinical findings, fluid analysis, and microbiologic results were retrieved.Results: Antimicrobials had been administered to equal proportions of cats and dogs before fluid sampling (45% and 47%). Groups did not differ in age or total protein concentration or percentage neutrophils in pleural fluid, but effusion cell count was significantly higher in cats than in dogs (P = .01). Neutrophils containing intracellular bacteria were identified in more cats (27/29, 93%) than dogs (44/60, 73%; P = .05). Penetrating damage to the thorax was implicated as the cause of pyothorax in equal percentages of cats (76%) and dogs (75%). Etiology could not be determined in 2 cats and 1 dog. Cats had higher numbers of bacterial isolates per patient (median, 3) than dogs (median, 1; P = .01) and anaerobes were isolated more often in cats (23/29, 73%) than in dogs (27/60, 45%; P = .003).Conclusions and Clinical Importance: Pyothorax had similar etiologies in cats and dogs. Cats had higher fluid cell counts, higher numbers of bacterial isolates identified per patient, and intracellular bacteria detected more commonly than did dogs.

Feline Infectious Peritonitis: European Advisory Board on Cat Diseases Guidelines

“…Once an effusion is sampled, the first thing to do is to take note of its appearance: if it is frank blood, or if it can be discerned as urine, FIP is very unlikely. Additionally, purulent exudates are usually not caused by FIP [ 252 ], although occasionally bacterial translocation in cats with effusions can complicate diagnosis (Séverine Tasker, personal communication). The presence of chyle will usually indicate other diseases, such as heart failure, lymphoma or a ruptured thoracic duct, but cats with FIP with pure chylous effusion have been reported [ 253 ].…”