34th Annual Scientific Meeting proceedings

Chylothorax is a condition characterized by the accumulation of chyle within the thoracic cavity. In dogs, the most common cause is Idiopathic or unknown.  This can lead to respiratory compromise and other complications in affected dogs. Thoracoscopic thoracic duct ligation has emerged as a minimally invasive surgical option for managing chylothorax, offering reduced postoperative pain and faster recovery compared to traditional open surgery. The added benefit of near-infrared teachnology has improved the accuracy and visualization during this procedure.

Preoperative Work-up
A thorough work-up for patients with chylothorax usually includes complete blood work (CBC, serum chemistry), fluid analysis (cytology, culture), heart worm testing, thoracic radiographs, echocardiogram, abdominal ultrasound, and most importantly CT lymphangiogram. This test allows for visualization of the thoracic ducts and many different anatomic variations have been found. In the author’s experience many times a bilateral approach is necessary to ligate all the ducts even though the main thoracic duct usually courses on the right side in dogs.

Lymphangiograms can be performed in many different ways but the author prefers:

Metatarsal pad- 1ml/kg non-ionic iodinated contrast bilateral for preoperative CT &

Metatarsal pad- Indocyanine green 1-2ml of 2.5mg/ml for intraoperative NIRF imaging

Procedure
Thoracoscopic thoracic duct ligation begins with the dog placed under general anesthesia and positioned in lateral or sternal* recumbency. The positioning is determined by the location and number of the ducts to be ligated. The 1^st port is placed at the 10th ICS for the camera and instrument ports are placed cranial and caudal to this. The caudal port can be an 11mm port to allow for Endoclips if desired.

Once inside the thoracic cavity, dissection dorsal to the aorta is carefully performed and then Indocyanine green is injected into a metatarsal pad. The thoracic duct is then identified and careful dissection performed to isolate the thoracic duct from surrounding structures, ensuring minimal trauma to surrounding tissues. Once adequately exposed, the thoracic duct is ligated using a vessel sealing device, surgical clips or ligatures to occlude the lymphatic flow.

Postoperative care typically involves pain management, antibiotic therapy, and monitoring for any signs of complications such as pneumothorax or recurrent chylothorax.

Advantages
Thoracoscopic thoracic duct ligation offers several advantages over traditional open surgery for chylothorax in dogs. These include:

1. Minimally Invasive: The procedure is performed through small incisions, resulting in reduced tissue trauma, postoperative pain, and shorter recovery times.

2. Improved Visualization: The thoracoscope provides enhanced visualization of the thoracic cavity, allowing for precise identification and ligation of the thoracic duct.

3. Benefits of NIRF: This technique uses fluorophores that are fast, convenient, safe (No known toxicity in veterinary medicine), and has multiple routes of administration (IV, peritumoral, subcutaneous, etc).

4. Reduced Complications: Minimally invasive techniques are associated with lower rates of complications such as wound infection and dehiscence.

5. Faster Recovery: Dogs undergoing thoracoscopic surgery typically experience faster recovery and return to normal activities compared to those undergoing traditional open surgery.

Thoracoscopic thoracic duct ligation is an effective and minimally invasive surgical option for managing chylothorax in dogs. Resolution rates range from 80-95% in dogs over the 3 months postoperatively but recurrence has been reported in 10-15% of cases long-term. The addition of other procedures such as pericardiectomy and cisterna chyli ablation have not been proven to add to efficacy in a recent meta-analysis.