Chylothorax in Cats


Chylothorax is a relatively rare condition in the cat in which lymphatic fluid or chyle accumulates in the pleural cavity between the lungs and the inner lining of the chest wall. The lymphatic system collects waste from the body’s tissues and returns it to the bloodstream. Chyle is the lymph fluid collected from the intestines. Since the intestines absorb fat from the cat’s diet, this fluid has a high fat content and milky appearance. When this fluid leaks into the chest cavity, it can partially collapse the lungs. This will cause breathing difficulties.

Symptoms of chylothorax

Symptoms will vary depending on the underlying cause of the fluid accumulation and the amount of fluid present, but may include any or all of the following:

  • Rapid or labored breathing (a cat’s normal respiratory rate is 20-30 breaths per minute)
  • Coughing
  • Inability to exercise
  • Pale gums and mucous membranes
  • Bluish discoloration of the skin
  • Depression and lethargy
  • Loss of appetite

What causes chylothorax?

The cause of chylothorax is mostly unkonwn (idiopathic). In some cases, trauma such as a fall or automobile injury that causes injury to the chest cavity may be the cause. Chylothorax may also be caused by tumors or lesions in the chest, heart or heartworm disease, and blood clots. There appears to be a genetic predisposition. Purebred cats, especially Siamese and Himalayan breeds, seem to be at higher risk.

Diagnosis of chylothorax

Your veterinarian will take x-rays to confirm the presence of fluid in the chest. A small amount of fluid is removed from the chest via a chest tap or thoracocentesis. Chyle is typically white or light pink in color. Laboratory tests can determine the fat content of the fluid; if it is high, it is most likely chyle. Examination under a microscope will show a large number of lymphocytes, a type of white blood cell that is only found in lymphatic fluid.

Treatment of chylothorax

Treatment will depend on the underlying cause, but the first step is a chest tap to remove the fluid from the chest cavity so the cat can breathe normally.

A supplement called rutin may be a beneficial treatment in some cats with chylothorax. It is thought to stimulate cells called macrophages to remove the fat in the chyle, and may reduce the amount of fluid accumulation.

A low fat diet is generally also recommended to lower triglyceride levels.


The prognosis is generally good if breathing can be stabilized. Cats may need multiple chest tap procedures and/or placement of a chest tube. Chylothorax has a high recurrence rate if the underlying condition cannot be identified. One of the most dangerous complications of chylothorax is fibrosing pleuritis, a process where scar tissue develops in the chest and permanently coats the lungs.

Ongoing care for chylothorax

Ongoing care may include periodic chest taps to remove fluid. Cats will need to be monitored for irregular breathing. Some cases of chylothorax will resolve spontaneously, but for some, there appears to be no effective treatment.

My personal experience with chylothorax

Feebee developed chylothorax as a complication from his intestinal lymphoma. Most likely, it was caused when the cancer metastasized into his lungs. He required a series of chest taps, but did fairly well on rutin therapy for several months before he came out of remission.

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