Chylothorax associated with constrictive pericarditis in a dog.

Chylothorax was associated with constrictive pericarditis in a 6-year-old mixed-breed dog. Clinical signs included hepatomegaly, bilateral jugular pulses, muffled heart sounds, and dyspnea. Pleural effusion was identified on thoracic radiographs. Thoracentesis yielded 3 L of chylous effusion, confirmed by the cholesterol/triglyceride ratio (0.14). Echocardiography revealed a thickened pericardium, with numerous fibrin tags, which was suggestive of constrictive pericarditis. Central venous, right atrial, and right ventricular pressures were high and on right ventricular diastolic pressure tracings, the square-root sign, which is indicative of constrictive pericarditis, was evident. Exploratory thoracotomy and pericardiectomy were performed. Histopathologic findings were consistent with chronic non-suppurative pericarditis. The dog's condition improved after surgery. On reevaluation 11 months later, central venous pressure and results of physical examination and thoracic radiography were normal. On the basis of these findings, we concluded that chylothorax was caused by constrictive pericarditis in this dog. Chylothorax is often associated with disorders that have a poor prognosis, but if constrictive pericarditis can be identified as the cause of the chylothorax, exploratory thoracotomy and pericardiectomy can provide a cure.