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Chylothorax in Dogs

Chylothorax in Dogs

Chylothorax manifests as an accumulation of lymphatic fluid in the chest cavity, encasing the heart and lungs (pleural cavity). The primary culprit behind this condition is chyle, a digestive fluid originating in the small intestine and conveyed by the thoracic duct to the veins. During its journey to the veins, chyle can seep into the chest cavity, where it accumulates, exerting excessive pressure on the chest and its organs.

Chyle presents as a milky to slightly yellow fluid composed of lymph and fats from the intestines, channeled into circulation through the thoracic duct—the primary trunk of the lymphatic system. This duct crosses the chest near the spine and empties into the circulatory system. Lymph, a watery fluid generated by the body’s tissues, contains white blood cells crucial for immune defense. Lymph travels through lymphatic vessels, transporting lymphocytes (white cells specializing in cellular immunity) and fats from the small intestines to the bloodstream.

Typically, when chyle accumulates in the chest cavity, it leads to blockage or obstruction of lymphatic vessels, causing vessel dilation and affecting the tissue covering the lungs and lining the inner chest cavity. This tissue becomes inflamed, resulting in scar tissue formation, which narrows the space and constricts the lungs, often resulting in severe breathing difficulties.

The Afghan Hound and Shiba Inu breeds are the most commonly affected by this disorder. While age does not seem to be a determining factor, chylothorax tends to develop in middle-aged Afghan Hounds and in Shiba Inus younger than two years old. This medical condition can affect both dogs and cats.

Symptoms and Types

Symptoms can vary depending on the root cause, the speed at which fluid has accumulated, and the amount of fluid present. Respiratory distress typically marks the initial indication of an issue, though if fluid buildup has been gradual, the condition might have been present prior to the onset of breathing difficulties. Several accompanying symptoms can aid in identifying the underlying cause of the respiratory problem. Your dog might exhibit some or all of the following symptoms:

  • Coughing
  • Rapid breathing
  • Elevated lung sounds
  • Dull heart and lung sounds
  • Irregular heartbeat
  • Heart murmur
  • Reduced ability to engage in physical activity
  • Depressive behavior
  • Loss of appetite and weight
  • Pallid gums and mucous membranes
  • Bluish tint to the skin


The etiology of chylothorax typically remains unidentified, although certain factors have been implicated as potential triggers. These include masses such as tumors within the chest cavity, nodular lesions resulting from fungal infections, blood clots within veins, cardiac surgery, heart disease, and heartworm disease. Additionally, there may be a congenital component involved in the development of this condition, suspected particularly in certain breeds. However, in most cases, the cause is generally categorized as idiopathic, meaning of unknown origin.


To diagnose chylothorax, your veterinarian will need to extract fluid from the chest. The presence of chyle in the fluid will aid the veterinarian in reaching a definitive conclusion regarding the underlying cause. Before fluid extraction, your veterinarian might opt to conduct an ultrasound examination of the chest to detect any masses within the thoracic cavity and to assess the structural integrity of the heart, ensuring accurate diagnosis. Chest X-ray imaging, both pre- and post-fluid removal, will provide the veterinarian with a clear diagnostic path. Additional imaging techniques may involve a computed tomography (CT) scan with a dye injection, offering a visual reference point as it traverses the system to more precisely reveal any blockages or obstructions.


The treatment plan will be contingent upon the underlying cause, with a primary intervention being a pleural tap to drain fluid from the chest cavity and alleviate breathing difficulties.

In cases where fluid accumulation is rapid due to trauma, chest tubes will be employed to promptly relieve pressure on chest organs and prevent lymphatic vessel dilation. If fluid continues to accumulate, ongoing use of chest tubes will be necessary to maintain chest clarity, with surgery likely recommended by your veterinarian. The most common and effective surgical approach involves ligating the thoracic duct and excising a portion of the pericardial sac surrounding the heart. Post-surgery, continued use of chest tubes may be necessary until your veterinarian is confident in the chest cavity’s ability to remain clear autonomously.

Furthermore, depending on the underlying cause, your veterinarian may prescribe medications for treatment, post-treatment care, or ongoing management.

Living and Management

Continued care and management will involve regular pleural taps to drain fluid from the chest cavity. Even after your dog shows signs of recovery, it’s important to have periodic evaluations for several years. Incorporating these assessments into routine veterinary exams should suffice unless advised otherwise. Vigilant monitoring for breathing difficulties or the reappearance of associated symptoms is crucial. While chylothorax may resolve spontaneously or following surgery, effective treatment options may not be available for some dogs.

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