Chylothorax

by: Dr. Theresa Welch Fossum

Chylothorax is a condition in which a characteristic type of lymph fluid called chyle accumulates in the chest cavity and causes difficulty breathing. Lymph is the fluid that is drained from tissues and functions to carry protein and cells from the tissues to the bloodstream via small vessels, known as lymphatics. When the lymph is drained from the intestines, it contains a high quantity of fat and is known as chyle. Thus, chylothorax is a collection of chyle in the chest cavity. The accumulation of chyle in the chest cavity leads to difficulty breathing because the lungs cannot expand normally to take in oxygen.

This condition may occur in any breed of dog, but some breeds appear to have a higher than expected incidence, including Afghan hounds and shiba inu dogs. Afghan dogs appear to develop signs related to this disease when they are middle-aged, whereas the shiba inu is often less than a year of age when the condition is diagnosed.

Chylothorax is most common in middle-aged and older animals, but can occur in very young animals as well.

The cause of the chylothorax in many animals idiopathic, which means the cause is not determined. However, some animals are determined to have tumors, heart disease or blood clots that elevate pressures in the bloodstream and cause the chyle to leak from the lymphatic vessels in the chest. It is important that underlying causes be identified and treated whenever chylothorax is diagnosed.

What to Watch For
Coughing
Difficulty breathing
Decreased appetite
Lethargy
Cyanosis
Diagnosis

If your pet is diagnosed with chylothorax, he will require veterinary care. Your veterinarian’s efforts will be directed at two things: making your pet more comfortable by removing as much of the fluid from the chest cavity as possible, and performing tests to determine whether there is an identifiable cause for the chylothorax. Diagnostic tests that your veterinarian may wish to perform include:

Chest radiograph. Chest radiographs or X-rays are done to confirm the presence of fluid in the chest cavity and to help determine how much fluid is present. After some of the fluid has been removed, a repeat X-ray is often done to evaluate the lungs to see if they can re-expand normally and to look for masses or other abnormalities in the chest cavity. Chest radiographs are also used to evaluate the size of the heart and blood vessels.

Chest tap. A chest tap (needle thoracentesis) is done to remove some fluid to allow your pet to breathe easier and also to obtain some fluid for analysis. A chest tap is done by inserting a small needle between the ribs and withdrawing the fluid into a syringe. Most animals tolerate chest taps and the procedure can be done without any sedation. However, occasionally, your veterinarian may need to give your pet some sedation or even general anesthesia in order to remove the fluid.

Fluid analysis. Chyle is a milky white fluid that contains a high concentration of triglyceride. Your veterinarian will run a triglyceride on the fluid removed from the chest cavity and compare it to the triglyceride content in a blood sample. If the chest fluid is chyle, the triglyceride level will be higher than the triglyceride in the blood sample.

Cytology (examination of the fluid under a microscope). Your veterinarian will also examine the fluid to determine whether there are abnormal cells, such as those that might indicate that a cancer is present, or whether infection is present.

Additional tests may be done to help determine the cause of the chylothorax and the overall condition of your pet. These tests might include ultrasonography of the chest, an echocardiogram (ultrasound of the heart) to evaluate heart function and various blood tests such as a heartworm test.

Treatment

If an underlying disease is found, your veterinarian will help you decide whether further treatment is warranted. The specific treatment depends on the underlying condition. If you elect to treat the underlying disease, your veterinarian will try to keep your pet comfortable by periodically removing the fluid to allow him to breathe more easily. Your pet may also be placed on various medications and a low-fat diet.

If an underlying disease is not found, your veterinarian may recommend that conservative treatment be tried to see if the chylothorax will resolve. This will usually include periodic removal of the fluid from the chest cavity and placing your pet on a low-fat diet. If the fluid accumulation does not decrease or resolve in two to three months, your veterinarian may suggest that surgery be performed.

An experimental drug that may help animals with chylothorax is Rutin. This drug is being evaluated to determine if it will help animals reabsorb the chyle from their chest cavity and decrease the severity of the scarring of the lining of the lung.

Home Care and Prevention

In addition to observing your pet closely for evidence of difficult breathing, you may also be asked to administer various medications. Be sure that your veterinarian shows you how to determine if your pet is having difficulty breathing and how to administer any prescribed medications.

If your pet is unwilling to eat commercial low-fat diets, your veterinarian should be able to provide you with recipes for homemade low-fat diets.

There is very little that you can do to prevent your animal from developing chylothorax. In many animals the underlying cause of the chylothorax is never determined.

Chylothorax can occur secondary to heart failure associated with heartworm disease; therefore, be certain to discuss your pet’s need for heartworm prevention with your veterinarian.
 

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Updated 21-10-05