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Background
Chylothorax is a result of thoracic duct damage with chyle leakage from the lymphatic system into the pleural space. It manifests as a pleural effusion on radiographs and computed tomography (CT). Causes of chylothorax can broadly be separated into non-iatrogenic or iatrogenic. Non-iatrogenic causes are most often related to malignancy, but traumatic injury can also cause chylothorax. Thoracic surgery or traumatic cannulation of thoracic vasculature can cause iatrogenic chylothorax. Chylothorax can present as a clinically impactful entity with potential to increase mortality. This can occur through loss of plasma proteins, fat-soluble vitamins, triglycerides, electrolytes, and intravascular volume. It has also been associated with increased risk of complications and death following surgical procedures such as esophagectomy when compared to patients without chylothorax. Utilizing fluorography and interventional radiology techniques, the thoracic duct and cysterna chyli can be opacified using carefully injected radiopaque materials and anatomic landmarks. Thoracic duct lymphangiography and thoracic duct embolization (TDE) is a relatively unique procedure that requires patience and dexterity to cannulate small structures. The purpose of this educational exhibit is to familiarize current and future radiologists with this procedure, review relevant anatomy, and demonstrate challenging cannulation of non-vascular structures.

Educational Goals / Teaching Points
Recognize pleural effusion on diagnostic imaging. Overview thoracic duct anatomy. Review necessary tools and commonly used materials used in the procedure. Outline and discuss lymphangiography and TDE. Discuss risks and complications of the procedure.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Key anatomic and technique-related issues including ultrasound-guided cannulation of small lymph nodes, propensity of lymphatic channels to rupture, locating and opacifying the cysterna chyli, and difficulty cannulating the thoracic duct after opacification. Pathophysiologic issues include sequelae of chylothorax on nutrient status, volume status, and impact on morbidity/mortality. Imaging findings of chylothorax on multiple modalities. Extravasation of contrast during lymphangiography and TDE.

Conclusion
Chylothorax is a clinically impactful entity that can increase morbidity and mortality. When compared to surgical ligation, TDE has improved clinical outcomes and decreased rates of morbidity and mortality. Additionally, lymphangiography can identify variant anatomy, which is often a complicating factor in the case of necessary surgical ligation. Although TDE can be a technically difficult procedure, it has few complications, primarily related to injected medications or intravascular device deployment.