Chylothorax in Dogs

This condition is often characterised by the inability of the patient to fully inflate their lung due to the buildup of fluid in the thorax. This buildup can lead to inflammation of the lungs and heart. Due to the potential for long-lasting harm, it is essential that your dog receives prompt treatment if you suspect they may be suffering from this condition.

Chylothorax is an uncommon, poorly understood disease in which chyle accumulates in the thoracic cavity. This may be caused by underlying heart conditions, trauma, cancer, fungal disease or blood clots; however, often the cause is idiopathic.

The symptoms displayed in a pet suffering from chylothorax are commonly seen in other respiratory illnesses such as pneumothorax. Signs may include:

• Non-productive cough
• Lethargy
• Appetite reduction or weight loss in chronic cases
• Breathing difficulties
• Tachypnea
• Cyanosis 

When left untreated this condition can cause irritation, inflammation and irreversible damage to the lungs and pericardium.

Chylothorax is caused by the buildup of the fluid chyle, which is lymphatic fluid, in the thoracic cavity. In a normally functioning canine, chylomicrons are produced following the ingestion of fats, these molecules are absorbed in the cisterna chyli and carried through the thoracic duct to the cranial vena cava. In canines suffering from chylothorax, a dysfunction in the thoracic duct leads to leaking of chyle into the thorax. This can result in difficulty breathing due to reduced lung inflation, weakened immune system, and metabolic disorders. There are many diseases that may cause this dysfunction such as cancer, fungal disease, and heart conditions such as murmurs and blood clots.

Your veterinarian will perform a full clinical examination. Signs that may indicate fluid in the thoracic cavity are muffled heart or lung sounds on auscultation. If your veterinarian suspects fluid in the thorax radiographs of the thoracic area may be performed. Your veterinarian may be able to visualise fluid in the thorax from the radiograph, allowing a diagnosis of pleural effusion to be made; however, she will not be able to confirm the presence of chyle. In order to determine the type of fluid present in the chest your veterinarian will likely perform a thoracentesis. In order to carry out this procedure sedation may be necessary for your pet. This procedure is performed by the veterinarian inserting a small needle between your dog’s ribs into the thoracic cavity and aspirating in order to obtain fluid. Through visual examination your veterinarian may suspect chylothorax due to the distinct, milky appearance. In addition, it may be sent for laboratory testing for confirmation. 

As chylothorax can be a secondary complication of underlying conditions further diagnostics such as thoracic or cardiac ultrasound or computed tomographic scans may be performed.

Immediate care

Your veterinarian will initially focus on trying to remove the chyle from the thoracic cavity of your pet in order to allow your companion to breath with full lung expansion. This may require a tube placed into the thorax or or intermittent thoracentesis. 

Surgery 

Your veterinarian may feel that thoracentesis will not be an effective treatment for your pet and choose to perform surgery to treat this disease. The two surgical options are: 

Thoracic duct ligation – This surgical method involves the ligation of the thoracic duct, preventing the chyle flow through this duct and instead forcing the body to develop new lymphatic connections to the venous system in the abdomen. 

Ablation of the cisterna chyli – This surgical method involves removing the cisterna chyli, causing the body to create new pathways for the lymph fluid to enter the bloodstream, allowing pressure on the thoracic duct to be relieved, and leaking of chyle into the thorax reduced.  

Recent studies have also shown that a pericardiectomy, the removal of the pericardium, may be beneficial in treatment of this condition. Your veterinarian will discuss with you the risks involved with this procedure. The surgery for chylothorax may be time consuming and due to decreased lung capacity and the respiratory effects of anesthesia agents, your dog is at an increased anesthetic risk.

Your dog will likely require hospitalization following the surgery. As anesthetic can cause hypothermia and excitement during the recovery period he will be provided with a warm, quiet environment during the postoperative period, in some cases oxygen therapy may also be indicated during this time. Your veterinarian may continue to drain your pet’s thorax intermittently using the chest tube. Your dog will be carefully monitored and once his chest tube is able to be removed he will be able to be discharged. 

Offer regular, palatable meals and encourage food intake during your pet’s recovery. A diet restrictive of fat may be indicated by your veterinarian. 

Regular revisit appointments are vital and intermittent, outpatient thoracentesis may be necessary if clinical signs present. The prognosis varies depending on the treatment given, however when successful you can expect full recovery within a few weeks of surgery.