Thoracic Duct Ligation in Dogs

Thoracic duct ligation is a surgical procedure used to treat chylothorax in dogs. During normal digestion, fat molecules from food pass through small lymph vessels known as lacteals before being transported into the cisterna chyli, the largest lymph vessel in the abdomen. These fat molecules then join the lymph fluid already present in the cisterna chyli. It is transported through the thoracic duct in the chest before entering the vena cava.

In dogs diagnosed with chylothorax, the thoracic duct leaks chyle into the chest cavity. As more chyle accumulates in the chest cavity, the lungs cannot fill with air, which causes difficulty breathing. Because chyle also contains important substances like protein, vitamins, and white blood cells, chylothorax may weaken the dog’s immune system. 

Thoracic duct ligation involves redirecting the flow of the lymph fluid into the abdominal veins rather than the thoracic duct. This usually resolves chylothorax. However, if the chylothorax is secondary to another condition, more treatment may be needed to fully resolve the condition. Additionally, more conservative methods may be recommended prior to surgery, especially if the condition can be managed through dietary changes or medication.

There are a few different approaches to this surgery, which will vary based on the underlying cause and the expertise and preferences of the surgeon. It may be performed as an open surgery or as a minimally invasive procedure which involves the use of a thoracic video camera. The procedure steps for both approaches are outlined below.

Open Approach

1. A blood sample will be taken to ensure anesthetization is safe for the dog.
2. General anesthesia and pain medications are administered intravenously.
3. The chest is shaved, cleaned, and clipped.
4. The surgeon will choose the appropriate surgical method for entering the thoracic cavity depending on their expertise and preferences. This can be achieved through an incision in the abdomen, along the sternum, or between the ribs.
5. The thoracic duct is identified.
6. Sutures or vascular clips are applied to the branches of the thoracic duct.
7. A chest tube is placed before the incision site is sutured.
8. The dog is hospitalized for up to five days.

Minimally Invasive Approach

1. Steps 1 and 2 are repeated.
2. The surgeon will make a small incision into the abdomen or chest.
3. A thoracoscope is inserted into the chest cavity. This is used to visualize the duct.
4. The surgeon will use long forceps to grasp the thoracic duct. 
5. Surgical staples are used to close the duct.
6. A chest tube is placed to drain excess fluid and air.
7. The dog may be hospitalized for up to five days.

Several complications may occur with thoracic duct ligation. These may include:

• Continued effusion in the chest cavity
• Failure to ligate all branches of the thoracic duct
• Recurrence of the condition
• The body fails to create new pathways
• Development of new collateral thoracic branches or lymph vessels
• Chyle effusion in other areas of the body

Up to 40% of dogs that undergo this surgery will experience persistent effusion. This effusion may or may not be chylous, and can resolve on its own or with the help of medication and additional treatment. The surgeon will discuss all possible complications with the owner prior to surgery.