Hemothorax in a Friesian horse: not always an aortic rupture!

A 16-year-old Friesian gelding was admitted to the Faculty of Veterinary Medicine (Ghent University) with complaints of exercise intolerance, pale mucous membranes, tachycardia and an irregular heart rate. General examination revealed decreased heart sounds and bronchovesicular sounds in the ventral lung fields, combined with a low hematocrit, which led to the suspected diagnosis of hemothorax. The diagnosis of hemothorax was confirmed by ultrasonographic examination of the thoracic cavity and thoracocentesis. Because it was a Friesian horse, aorto-pulmonary fistulation was suspected, but this was excluded by thorough echocardiographic examination. The electrocardiogram showed that the irregular heart rate was caused by atrial premature contractions. The horse was hospitalized and was treated conservatively with broad spectrum antibiotics. Because both the hematocrit and the ultrasonographic images evolved well, the horse could leave the clinic after 15 days. Re-examination after six weeks showed no more abnormalities.