Thoracic Duct

ductus thoracicus

The thoracic duct is the largest lymphatic vessel in the body, draining the entire lower body and the left side of the upper body. It originates at the cisterna chyli at L1-L2, ascends through the posterior mediastinum to the right of the aorta, crosses to the left side at T4-T5, and empties into the venous system at the junction of the left internal jugular and subclavian veins. It carries approximately 2-4 litres of chyle per day.

Region: Chest

Clinical Relevance

Clinical Notes

Thoracic duct injury during oesophagectomy, cervical lymph node dissection, left subclavian artery surgery, or trauma produces chylothorax, presenting as milky pleural effusion with high triglyceride content. Low-output chylothorax responds to medium-chain triglyceride diet or NPO with TPN; high-output cases require surgical ligation of the thoracic duct at the level of the diaphragm or thoracoscopic clipping. Thoracic duct embolisation via transhepatic lymphangiography is a successful minimally invasive alternative.

Pathology

Common Injuries & Conditions

Chylothorax from Thoracic Duct Injury

Surgical or traumatic injury to the thoracic duct produces chylothorax with a milky pleural effusion containing chylomicrons and triglycerides above 110 mg/dL, managed by dietary modification and pleural drainage for low-output leaks and by thoracoscopic duct ligation at the diaphragmatic hiatus for persistent high-output leaks.