Anatomical variations of the thoracic duct in the dog

Anatomical variations can be frequently found in the lymphatic system, which is also true for the shape and course of the thoracic duct (ductus thoracicus), the biggest lymph vessel in the body. From 2012 to 2019, the thoracic duct was successfully dissected in 43 dog carcasses that were used in the anatomy course at the Faculty of Veterinary Medicine, University of Zagreb. The thoracic duct originated from the cranial border of the cisterna chyli as one lymph vessel in 36 dogs (83.7%), as two vessels in six dogs (14%) and as three vessels in one dog (2.3%). We divided the observed thoracic duct variations into six groups according to their anatomical similarities. Considering the specific embryonic development, we can conclude that all observed variations are the result of minor deviations from the standard ontogenesis. However, the importance of thoracic duct variations is significant in surgical procedures done in the thoracic cavity to prevent or cure the chylothorax. Since this research showed variations in 39 out of 43 dogs (90.7%) throughout the whole course of the thoracic duct, great care must be taken while performing the ligation or embolization of the thoracic duct.