Chylothorax in cats: is there a role for surgery?

Abstract

Chylothorax is a complex disease with many identified underlying causes including cardiac disease, mediastinal masses, heartworm disease and trauma. Management of this disease should be directed at identifying the cause, if possible, and treating the underlying disorder. In cats with idiopathic chylothorax, medical management is recommended initially because the condition may resolve spontaneously. Owners should be made aware of the potential development of fibrosing pleuritis in affected cats. When medical management is impractical or unsuccessful, surgical intervention should be considered. Surgical options include mesenteric lymphangiography and thoracic duct ligation, pericardiectomy, omentalisation, passive pleuroperitoneal shunting, active pleuroperitoneal or pleurovenous shunting, and pleurodesis. Of these, only thoracic duct ligation and pericardiectomy are preferred by the author because, if successful, the result is complete resolution of the chylothorax, thereby reducing the risk of developing fibrosing pleuritis. Omentalisation may be beneficial in some animals as adjuvant therapy, but this procedure may still allow fibrosing pleuritis to occur. Until the aetiology of the effusion in cats with idiopathic chylothorax is understood, the treatment success rate will be less than ideal. Future research needs to be directed at determining the pathophysiologic mechanisms underlying this disease in cats.

Fig 1.

Photomicrograph of the lungs of a cat with fibrosing pleuritis associated with chylothorax. Notice the thickened pleura and the rounded appearance of the lung lobes.

Fig 2.

Lateral view of lungs of a cat with chronic chylothorax. Notice the severe atelectasis and rounded appearance of the cranial lung lobes.

Fig 3.

Lymphangiogram performed in a cat with chylothorax and thoracic lymphangiectasia. Note the multiple, dilated lymphatics near the entrance of the thoracic duct (arrow) into the venous system.

Fig 4.

Identification of the thoracic duct can be aided by injecting methylene blue into the lymphatic catheter, or directly into a mesenteric lymph node.

Fig 5.

Diagram depicting placement of a pleuroperitoneal shunt. The pump chamber should be positioned over a rib so that it can be manually compressed. (Reproduced from Fossum (ed.) Small Animal Surgery, Mosby, Publishing Co. 1997.)