Thoracic duct in cats (Felis catus)

To describe the origin, course and termination of the thoracic duct in cats, eight adult healthy cats of both sexes and of different ages, were examined. Abdominal cavity was opened with a median incision under general anaesthesia. Then, Indian ink was injected into the lymph nodes of the abdominal cavity, and into the popliteal lymph nodes. After exsanguination by the conventional methods, the animals were fixed with 10 % formalin. Then, the thoracic duct was investigated by dissection. In all cats the thoracic duct arising from the craniodorsal part of the Cisterna chyli as a single trunk at the level of L2 entered the thoracic cavity through the aortic hiatus of the diaphragm. In the caudal and middle mediastinum it had a rope ladder appearance around the intercostal arteries and dorsal to the thoracic aorta. Forming a single trunk at the level of T8, it ran cranioventrally up to the level of the cranial thoracic aperture. At this level the thoracic duct joined as a single duct the left external jugular vein in six cats, and the venous angle in two cats. Between T1 and T2, the thoracic duct was divided into two parts 1 cm before entering the venous system in one cat. During its course as a single channel the thoracic duct had a beaded appearance because of having valves. In the light of the normal anatomical position of the thoracic duct in the cat we suggest that the thoracic duct may be cannulated in its initial and terminal portions.