Chylothorax

Chylothorax is the accumulation of chyle in the pleural space resulting from disruption or obstruction of the thoracic duct or its major tributaries. Chyle is lymphatic fluid rich in triglycerides, chylomicrons, proteins, and lymphocytes that normally drains from the intestinal lymphatics into the venous system. When leakage occurs, pleural fluid can be milky and rich in triglycerides.

Causes are broadly categorized as traumatic or iatrogenic, malignant, congenital, or miscellaneous. The most common causes are thoracic or neck surgery and other injuries to the thoracic duct; malignancy, especially lymphoma; and less commonly infectious or inflammatory conditions, or congenital defects in children.

Diagnosis is suspected in a patient with a pleural effusion and a milky or turbid fluid, particularly after meals. Pleural fluid analysis typically shows a high triglyceride concentration (often >110 mg/dL) and the presence of chylomicrons. The fluid is usually exudative by Light’s criteria. Localizing the leak can be aided by imaging such as lymphangiography or lymphoscintigraphy; these studies help guide therapy.

Management aims to reduce chyle flow and treat the underlying cause. Initial measures include drainage of the effusion for symptoms and nutritional support. Dietary modification with a medium-chain triglyceride diet or total parenteral nutrition reduces chyle production. Pharmacologic options such as octreotide may be used in some cases. Persistent or high-output leaks may require interventions to close or bypass the leak, including thoracic duct ligation, thoracic duct embolization, or pleurodesis.

Prognosis varies with etiology and response to therapy; malignant causes portend a worse outcome, while many patients recover with appropriate management and nutrition.