Our goals for surgery associated with the treatment of chylothorax include complete ligation of the thoracic duct(s), relief of pericardial pressure on the heart, relief of lymphatic pressure behind the thoracic duct. This is all in an effort to cause the formation of new lymphaticovenous anastomoses in the abdomen, bypassing the thoracic ductal anatomy completely.

Thoracic Duct Ligation (TDL)

The thoracic duct is typically ligated as far caudal in the thorax as possible. Our initial belief was that the new lymphaticovenous anastomoses would occur in the abdomen. Research has shown that the fewest number of duct branches are present ventral to T12-L1. This should simplify surgery; however, beware, the cisterna chyli may actually cross the diaphragm, which increases the risk of laceration and leakage upon dissection.

The certainty of complete can be aided with pre-operative lymphangiography, post-operative lymphangiography, pre-ligation coloration of the thoracic duct, and post-ligation coloration. It was also believed that small, nonpatent ducts may be the source of failure following TDL, so pressurization of the lymphatic system following TDL has been suggested as an important adjunct to TDL. Lymphangiography can be done prior to TDL for anatomical mapping of the system and can be repeated after TDL to ensure that all ducts have been ligated. Access can be via mesenteric lymphatic catheterization, mesenteric lymph node injection, and popliteal lymph node injection. Minimally invasive techniques include ultrasound guided mesenteric lymph node injection, laparoscopic lymph node injection and use of the popliteal lymph node. Ultrasound guidance has been described with the patient in dorsal recumbency using 27-G, 1¼-inch needles and 1.5–2 ml of contrast with 120-sec injection times. Similarly, laparoscopic guidance using a 2-port technique and a 22-G, 2½-inch spinal needle and 22 ml/kg of contrast. Success using laparoscopy was described in 6/10 animals, but the procedure should be done rapidly, loss of detail occurred within 3–4 min. Popliteal lymph node injection can be done with the patient in lateral or sternal recumbency using a 25-G butterfly needle and 6–10 ml iohexol injected over 2.5 to 5 min. Studies also compared CT to radiographs and showed that diluted contrast on CT scan was more accurate than radiography in dorsally recumbent experimental dogs. CT was also superior to radiographs when the popliteal lymph node was used for infusion of contrast through a 25-G butterfly needle over 4–5 min. Refinement of the technique was described using a 2-min delay for CT, but achieving the study within 13 min was important in dorsally recumbent experimental animals. Coloration of the thoracic duct can be done with single, one-time injection of the popliteal lymph node or mesenteric lymph node. Coloration was achieved within 10 min and lasted up to 60 min. Bilateral popliteal lymph node injection may be required, as only 6/10 were successful with a single injection. Significant accumulation of dye in the sublumbar lymph nodes was noted. Injection of the diaphragm with methylene blue was not overly successful in experimental animals. The use of indocyanine green and special camera and filter combinations may represent the future and can also be done thoracoscopically to aid in identification of thoracic duct branches for ligation.

Thoracoscopy may greatly decrease the morbidity associated with the approach for TDL and increases the lighting and magnification for TDL. General notes for success seem to also include stabilizing the lymph node used for injection and slow injection to avoid leakage of contrast or dye.

Cisterna Chyli Ablation (CCA)

CCA may decrease the pressure caudal to thoracic duct ligation, perhaps decreasing the risk of formation of collaterals and to decrease the opening of nonpatent thoracic duct branches after TDL. It may also help to encourage extrathoracic anastomoses between the lymphatic and venous systems.

CCA was classically described in dorsally recumbent patients but can be done in sternal recumbency. It may be done following TDL and coloration of the lymphatic system, which should improve the ability to visualize the cisterna chyli. Laparoscopic CCA was described cranial to the left renal artery and dorsal to the aorta for complete CCA to be done and to ensure no patent branches coursed cranially to the thoracic duct. We currently perform TDL, inject either the popliteal or mesenteric lymph node over a period of 2–5 minutes and monitor for distention and coloration in the caudal thorax. Any blue coursing cranial to the site of TDL must be ligated and can be bilateral. Once the TDL is complete and no further blue courses cranial in the thorax, CCA can be done, and the system should be easily seen if colored blue and pressurized (distended).

Pericardectomy

Pericardial windows have been shown to be ineffective. Subtotal, open pericardectomy or thoracoscopic subtotal pericardectomy should be done. The author has done pericardial window for the harvesting of a sample for histopathology and culture followed by "banana peel" of the remaining pericardium. This technique should eliminate pressure on the heart and should prevent the possibility of reformation of the pericardium or adherence to the heart.

Single Approach for TDL & CCA

A single, modified parcostal approach has been described for TDL and CCA in the dog. This should also decrease the morbidity of two separate approaches (intercostal and paracostal or complete median sternotomy and ventral laparotomy). Considerable lateral traction to the ribs may be required for large, overweight patients with chylothrax. A transdiaphragmatic approach has also been described in cats. The author commonly uses a thoracoscopic and laparoscopic assisted techniques for cats. Anecdotally, the popliteal lymph nodes of cats with chylothorax are often quite small and difficult to use for infusion of contrast or dye, whereas the mesenteric lymph nodes are accessible and can be used for slow infusion of adequate volumes of contrast or dye.