Chylothorax in dogs and cats: surgical therapy options

A chylothorax is an uncommon condition in dogs and cats and often considered to be a diagnostic and therapeutic challenge for the veterinarian. It has several potential underlying causes. An idiopathic chylothorax frequently has no identifiable predisposing cause. Diagnostics include an ultrasound of the thorax to detect any fluid, with simultaneous thoracentesis to stabilize the patient, along with a subsequent X-ray examination of the thorax to identify any visible causes. A complete pleural fluid evaluation, blood testing including hematology, blood chemistry and coagulation analysis are also part of the diagnostic workup. Furthermore, an echocardiography and an examination for heartworms (PCR, antigen detection) and, in cats, testing for the feline leukemia virus (FeLV) and the feline immunodeficiency virus (FIV) should be carried out. Computed tomographic lymphangiography, through which the thoracic duct and pathological lymphangiectasias and leaks can be identified, is used as additional diagnostic imaging and to improve operative planning. The intraoperative visualization of the thoracic duct is achieved by injecting methylene blue or a fluorophore into the ileocecal lymph node. The treatment of a chylothorax depends on the cause. If a cause cannot be determined, conservative and surgical methods of treatment do exist. Because of the rather poor outcome of sole conservative therapy (repeated thoracentesis, dietary management), surgical treatment consisting of one or more methods is often advised. The closure of the thoracic duct should always be part of the surgical intervention. Other techniques that can be combined are subtotal pericardiectomy, ablation of the cisterna chyli, omentalization of the thorax and decortication in the case of fibrosing pleuritis. Even with surgical therapy, the prognosis is considered to be guarded. The presence of fibrosing pleuritis, as in chronic chylothorax, usually indicates a poor prognosis.