Retrospective evaluation of dogs presenting with hemothorax

Clinical research into hemothorax in dogs in the veterinary literature is limited, with no data assessing diagnostic criteria and prognostic factors.

Describe etiologies, clinical features, treatments, outcomes, and prognostic indicators in dogs presenting with hemothorax, and assess the prevalence of dogs meeting different definitions of hemothorax.

Eighty-four client-owned dogs presenting with hemothorax to a university teaching hospital (2014-2024).

Single-center retrospective cohort study in the United Kingdom reviewing medical records. Cases were categorized according to their recorded cause. Selected variables were compared to survival to discharge. Varying definitions of hemothorax were compared.

Neoplasia (53/84, 63%), specifically hemangiosarcoma (19/53, 36%), was the most common cause of hemothorax. Pleural effusion packed cell volume (PCV) or hematocrit (HCT) > 25% that of peripheral blood was the least stringent criterion for diagnosis of hemothorax with all cases meeting this criterion. The overall survival to discharge rate was 51/84 (61%). Dogs with a neoplastic cause for their hemothorax were more likely to survive to discharge if they had surgery to address hemothorax (P < .001; odds ratio 15.0; 95%CI, 2.74-159) or if they were found to have pleural effusion PCV or HCT < 50% that of peripheral blood (P = .01; odds ratio 0.075; 95%CI, 0.002-0.641).

Causes of hemothorax are diverse, with neoplasia being the most common. A universally recognized definition of hemothorax would be beneficial. Surgical management and pleural effusion PCV or HCT < 50% that of peripheral blood are positive prognostic indicators. Dogs with hemothorax can have a good short-term prognosis.