Chylothorax is the accumulation of a milky fluid within the chest

If medical therapy is ineffective, surgery is warranted

Prognosis is somewhat guarded

What is it?

• Chylothorax develops when chyle, a fatty lymphatic fluid accumulates in the chest cavity, outside the lungs (called the pleural space).  
• Chyle normally empties from the intestinal lymphatics (which are lymph system vessels) into the veins in the chest cavity.
• Causes of chylothorax in dogs include congenital (present at birth) abnormalities of the lymphatic system (leaky lymph system vessels), diaphragmatic hernia, fungal infection, heartworm disease, twisting of a lung lobe, trauma/rupture of part of the lymphatic system, or due to an unknown cause.
• Causes of chylothorax in cats include heart disease, cancer, trauma/rupture of part of the lymphatic system, heartworm disease, or due to an unknown cause.
• In a majority of animals, despite extensive diagnostic work-ups, the underlying cause is undetermined. There does not seem to be a gender predisposition. Breeds at higher risk for chylothorax include Afghan Hounds, Mastiffs, and purebred cats.

Diagnosis

• Diagnosis is based on physical examination, clinical signs, chest x-rays, and analysis of the fluid in the chest cavity. The fluid is typically milky white and contains a high level of triglycerides (fat). Chylous fluids usually have triglyceride levels that are 12 to 100 times greater than the levels measured in the blood. Once chylothorax has been diagnosed, further diagnostic tests are performed to identify potential underlying disease. These may include ultrasound of the chest and its internal structures, heartworm test, and in cats, measurement of thyroid hormone levels.

Clinical signs

• The most common presenting sign of chylothorax is difficulty breathing.   Other clinical signs and historical findings include weight loss, inappetance, gagging, coughing, regurgitation, vomiting, exercise intolerance, and salivation.

Treatment

• Depending on the cause, treatment of chylothorax may be medical or surgical. An underlying disease process should be identified and corrected if possible.
• Medical management is directed at draining the fluid in the chest and reducing the formation of chyle.
  • Pleural drainage is indicated to relieve breathing difficulties and may either be intermittent or continuous via a chest tube.
  • A low-fat diet may decrease the amount of fat in the chest fluid, which may improve the animal’s ability to resorb fluid from the chest.
  • Rutin (a compound extracted from the fruit of the Brazilian Fava D’Anta tree) administration may result in clinical improvement of cats with idiopathic chylothorax.
• Surgical management typically is performed in cases where medical management has failed. Various surgical options are available, the most common of which is ligation of the thoracic duct (a lymphatic vessel). Removal of the sac surrounding the heart may also be beneficial. A report on ablation of the abdominal lymphatic vessels (cysterna chyli) has shown excellent results, although the series of cases only included a small number of patients.

Potential complications

• A common complication of medical therapy is recurrence of the fluid.
• Chyle is irritating to the outside covering of the lungs and chest cavity (the pleura), causing fibrin and connective tissue formation on the outside of the lungs. A common sequela to chylothorax is restrictive pleuritis, resulting in an inability to expand the lungs...even if the chylothorax resolves.
• Lung lobe torsion (twisted lung lobe) may be a primary cause of the problem, but also may be a complication of chylothorax.
• Infection is a potential complication following surgery, however this is uncommon.
• Anesthetic death is possible, however, under the care of our specialists, this is uncommon.

Prognosis

• Despite vigorous attempts at medical and surgical management, a significant percentage of animals with chylothorax will fail to respond to therapy. The prognosis for chylothorax is guarded, unless it is traumatically induced or the result of a reversible condition.

References

• Ettinger SJ, Feldman EC. Chylothorax. In: Textbook of Veterinary Internal Medicine. 5 th Edition. Philadelphia: WB Saunders Company, 2000; 1107-1109.
• Monnet, E. Management of Pleural Effusion. Western Veterinary Conference 2002.
• Nelson RW, Cuoto CJ. Chylothorax. In: Small Animal Internal Medicine. 2 nd edition. St. Lous: Mosby, Inc, 1998; 331-333

< Back to Article Index | Top of Page

What is a Board-certified surgeon?

Click here to find out!