Non-coagulopathic spontaneous hemothorax in dogs

Objective: To determine the history, clinicopathologic findings, underlying causes, and outcomes for dogs with non-coagulopathic spontaneous hemothorax. Design: Retrospective case series. Setting: University referral hospital. Animals: Sixteen client-owned dogs. Interventions: The medical records database was searched for dogs with hemothorax. Dogs with trauma, secondary coagulopathy, recent thoracic surgery, or pericardial intervention were excluded. For the remaining dogs, signalment, clinical signs, clinicopathologic findings, radiographic findings, histopathologic findings, interventions, and outcome were recorded. Measurements and main results: The most common presenting signs were tachypnea (n=9) and lethargy (n=5), typically of < 1-week duration. The most common cause of non-coagulopathic spontaneous hemothorax in dogs was neoplasia, which was diagnosed in 14 patients (88%). Identified malignancies included hemangiosarcoma (n=1), malignant mesothelioma (n=1), metastatic ovarian carcinoma (n=1), osteosarcoma (n=2), and pulmonary carcinoma (n=2). An intrathoracic mass was visualized in 7 other dogs; however, histopathology was not obtained. Pancreatitis and lung lobe torsion were each diagnosed in 1 dog, and survival was prolonged with both surviving at least 1 year post discharge. Only 6 of 14 dogs that were diagnosed with neoplasia were discharged from the hospital. For the 4 dogs with cancer with available outcome data, median survival time was 16 days (range 1-70 days). Two dogs were lost to follow-up and had unknown survival times. Conclusions: The development of non-coagulopathic spontaneous hemothorax warrants a high-index suspicion for neoplasia, in particular thoracic wall neoplasia.