LLT can be idiopathic or secondary to pleural effusion, other pulmonary or pleural space disease, trauma, or thoracic surgery.1,2 Deep-chested, large-breed dogs (especially Afghan hounds) and certain small-breed dogs (eg, pugs) have been reported to have a higher occurrence of LLT.1-6 Lobectomy of the affected lung lobe is the treatment of choice for LLT. Previously, survival rates were 50% to 78%1,2,6; however, more recent studies report a survival-to-discharge rate of 92%.4
Chylothorax can occur secondary to intrathoracic pathology that causes obstruction of the thoracic duct and normal lymph flow. Common causes include granuloma, trauma, congenital abnormalities of the thoracic duct, diaphragmatic hernia, cardiac disease, thoracic surgery, and intrathoracic neoplasia.7,8 Although the underlying cause of chylothorax should be treated, a primary cause (ie, idiopathic chylothorax) is not identified in many cases.7
Chylothorax is a common pre- and postoperative finding with LLT.1,2-5,9 Pleural effusion is thought to increase the risk for LLT, and chylothorax that develops after lung lobectomy may be caused by trauma to the thoracic duct during surgery or pleuritis from LLT, which alters lymphatic flow.1,2,9 When LLT is diagnosed and pleural effusion is present, presurgical serum and fluid triglycerides should be tested to diagnose chylous effusion, as chyle may not always have a milky appearance, and the presence of chylothorax may warrant additional surgical procedures at the time of lung lobectomy.5
Several therapeutic options are available for idiopathic chylothorax.10-16 Medical options include feeding a low-fat, medium-chain triglyceride diet and administering rutin (a benzypyrone) with or without octreotide (a somatostatin analog). Medical therapy alone has a low success rate (eg, 40%).10-12 Surgical options include ligation of the thoracic duct, subtotal pericardiectomy, and cisterna chyli ablation. Success rates of 53% to 88% have been reported when these surgical procedures are used in combination.10,13-16 Other surgical procedures with variable success rates have also been reported, including thoracic omentalization, pleurodesis, placement of pleuroperitoneal or pleurovenous shunts, and placement of permanent pleural space catheters for intermittent evacuation of fluid.10,13-16