Intrapericardial cystic hematoma in a dog treated by thoracoscopic subtotal pericardectomy

CASE DESCRIPTION A 2-year-old castrated male mixed-breed dog was evaluated because of a 1-week history of respiratory distress and abdominal distension. Thoracic radiography and echocardiography at that time revealed an enlarged cardiac silhouette and pericardial effusion; abdominal radiography and ultrasonography revealed ascites. CLINICAL FINDINGS At the initial referral examination 5 weeks later, the dog weighed 37.5 kg (82.5 lb) and appeared clinically normal. The only abnormality detected was a grade I/VI systolic murmur on the left side of the thorax. Echocardiography revealed a large fat- and fluid-filled cystic structure located next to the right ventricle with scant pericardial effusion. Computed tomography revealed a bilobed peripherally contrast-enhancing structure within the right ventral aspect of the pericardium; the right ventricle appeared compressed by the cyst. TREATMENT AND OUTCOME Initial treatment consisted of pericardiocentesis and abdominocentesis to alleviate clinical signs. Thoracoscopic subtotal pericardectomy was performed 6 weeks after the initial treatment. The cyst was completely excised, and multiple adhesions between the visceral and parietal pericardium were transected, without surgical or anesthetic complications. Histologic examination of the cyst revealed chronic inflammation with histiocytic infiltration, suggesting possible foreign body reaction or chronic inflammation and hemorrhage. These findings supported a diagnosis of cystic hematoma of the pericardium. The dog remained clinically normal for at least 16 months after surgery. CLINICAL RELEVANCE This report represents a rare case of intrapericardial cystic hematoma in a dog. Minimally invasive surgery was performed without complications, suggesting that thoracoscopic subtotal pericardectomy is a feasible treatment option for affected dogs.