Chylothorax in Cats

Normally, the cat’s body maintains about one teaspoon of clear fluid in this space, which helps to lubricate the surface of the lungs. In chylothorax, the fluid is cloudy and present in a much greater amount. Purebred cats are more likely to develop this disease than mixed breeds. It is important to have affected cats examined by a vet, because the condition can be fatal if left untreated.

When a cat begins having sustained difficulty breathing, one possible diagnosis is chylothorax. In this condition, lymphatic fluid (chyle) begins to build up between the lungs and the interior lining of the cat’s chest wall. The vet makes a diagnosis based on the appearance of the fluid as well as how much fluid is removed from the pleural cavity.

In the early stage of chylothorax, the cat’s symptoms may not seem serious:

• Cough
• Labored breathing
• Cat appears to “hold” its breath
• Chest pain
• Fever
• Loss of appetite
• Lethargy
• Possible weight loss
• Possible depression
• Avoidance of exercise

In the life-threatening stage, the cat may develop heart failure. This is possible only because the cat learns to adapt its physical activity to its abilities, which makes it easier for the owner to miss this illness.

When the vet suspects chylothorax in a sick cat, they have to do some detective work in determining the cause of this disease. In some cases, the cause of the illness has to be treated as the chylothorax is treated:

• Trauma to the cat’s chest (leads to the thoracic duct becoming “leaky”)
• Increased pressure inside the thoracic duct
• Increased pressure within the vena cava

An increase of pressure within the thoracic duct or vena cava can be caused by:

• Chest tumor or cancer
• Congestive heart failure (CHF)
• Fungal infection
• Heartworm infection
• Kidney disease

If the vet cannot determine the cause of the chylothorax, the disease is defined as “idiopathic” or having an unknown cause.

A physical exam is necessary for the vet to get a diagnosis of chylothorax. They will listen to the cat’s chest, heart and lungs with a stethoscope (auscultation). If the cat has fluid in its pleural cavity, heart and lung sounds will be muffled.

Once the vet begins to suspect a fluid build-up, he or she will order X-rays, which will show the presence of the fluid. This doesn’t provide a solid diagnosis of chylothorax, though.

To narrow the diagnosis down, the vet will insert a small-gauge needle into the thoracic area and withdraw some of the fluid. Depending on the cat, it may be necessary to place the animal under sedation to complete this particular test. If the fluid is thick and milky-white, it is called “chyle,” which is a lymphatic drainage that originates in the thoracic ducts. 

Along with aspirating some of the fluid, the vet will take a blood sample, which helps to determine a chylothorax. 

Once the vet has diagnosed a chylothorax, they will begin working to determine the cause. This involves an ultrasound of the thoracic cavity and the heart, which may determine the presence of heartworms. It may also be necessary to obtain a CT scan, which can help to determine whether the cat has cancer in its chest or some form of heart disease.

The cat will also undergo a feline leukemia (FeLV) blood test and testing for the presence of heartworms.

Stabilization

Before any other treatment, the cat’s condition has to be stabilized. This is done by draining the accumulated fluid so the cat can breathe more normally. Fluid is drained using a syringe and needle. The cat will be given supplemental oxygen to make breathing easier. If the cat is extremely stressed, it may need to be sedated.

Supplemental Treatment

The vet may prescribe rutin, which works to stimulate the development of cells called “macrophages” that remove fat in the chyle and slow the speed of fluid accumulation. The cat will be placed on a low-fat diet, which helps to lower triglyceride levels.

Surgical Treatments

If the fluid begins building up again, the cat will have a chest drain surgically implanted. This drain will be removed once the accumulation of chyle slows down and stops. This tube is drained frequently (every four to six hours) for at least one week after surgery.

Another surgical treatment is the ablation (burning or tearing) of the cistema chyli (CCA). This area holds lymphatic fluid in the abdomen. The ablation surgery obliterates this area and makes it possible for the cat’s body to form another pathway for the lymph fluid to enter the bloodstream.

Once a cat has developed a chylothorax it can return, which means the cat’s condition will need to be monitored after the first chylothorax has been resolved. If chyle builds up repeatedly, the cat is at risk of developing fibrosing pleuritis, which is untreatable once it develops. Chylothorax with a solid diagnosis of an underlying condition means the cat has a better prognosis; idiopathic chylothorax comes with a poor prognosis.

At home, the cat owner should watch the pet closely for increased breathing difficulty. If this develops, the cat may seem uncomfortable or short of breath. The cat’s low-fat diet will need to be maintained at home.

The cat’s prognosis is good once breathing is stabilized and the chylothorax and underlying condition are treated. If the underlying disease doesn’t return, the cat’s prognosis remains good. Watchful pet owners who are able to detect the first symptoms also help to improve the cat’s chances of survival.