The thoracic duct: clinical importance, anatomic variation, imaging, and embolization.

UNLABELLED: The thoracic duct is the body's largest lymphatic conduit, draining upwards of 75 % of lymphatic fluid and extending from the cisterna chyli to the left jugulovenous angle. While a typical course has been described, it is estimated that it is present in only 40-60% of patients, often complicating already challenging interventional procedures. The lengthy course predisposes the thoracic duct to injury from a variety of iatrogenic disruptions, as well as spontaneous benign and malignant lymphatic obstructions and idiopathic causes. Disruption of the thoracic duct frequently results in chylothoraces, which subsequently cause an immunocompromised state, contribute to nutritional depletion, and impair respiratory function. Although conservative dietary treatments exist, the majority of thoracic duct disruptions require embolization in the interventional suite. This article provides a comprehensive review of the clinical importance of the thoracic duct, relevant anatomic variants, imaging, and embolization techniques for both diagnostic and interventional radiologists as well as for the general medical practitioner. KEY POINTS: • Describe clinical importance, embryologic origin, and typical course of the thoracic duct. • Depict common/lesser-known thoracic duct anatomic variants and discuss their clinical significance. • Outline the common causes of thoracic duct injury and indications for embolization. • Review the thoracic duct embolization procedure including both pedal and intranodal approaches. • Present and illustrate the success rates and complications associated with the procedure.