A two year old male intact Borzoi presented with a three week history of exercise intolerance, lethary, and inappetence. Physical examination reveated an irregular heart rhythm, muffled heart sounds on the right side, and decreaed lung sounds ventrally on the right side. EKG showed frequent ventricular premature complexes. Echocardiogram disclosed tricuspid valve dysplasia with mild dilation of the right side of the heart. Thoracic radiographs revealed a consolidated right middle lung lobe with mild pleural effustion. Pleural fluid analysis showed an exudative effusion with suppurative inflammation. An exploratory thoracotomy confirmed torsion of the right middle lung lobe, which was removed. Pleural fluid collected during surgery revealed chylous effusion. The dog was diagnosed with idiopathic chylothorax when chylous pleural fluid continued to accumulate after survery. After not responsing to one month of medial management for chylothorax, the patient returned for a thoracic duct ligation, pericardectomy, and cisterna chyli ablation.