A chylothorax (plural: chylothoraces) refers to the presence of chylous fluid in the pleural space often as a result of obstruction or disruption to the thoracic duct. It may be congenital or acquired.


Chylothoraces may present with variable pleural fluid appearance and biochemical characteristics; they are usually exudative. Gross appearance of the fluid is generally considered not a sensitive diagnostic criterion for a identifying chylothorax. A non-milky appearance is common (i.e. can occur in over 50% of cases). Chylous effusions can rarely be transudative (especially in patients with cirrhosis).


It can be due to direct injury to the lymphatic ducts or due to obstruction of the ducts and fragile collateral formations which are prone to spontaneous rupture. Common causes include:

  • malignancy
    • lymphoma: generally thought to be the most common non-traumatic cause 
    • metastases
  • iatrogenic: post thoracic and abdominal surgery, in particular esophagectomy and block dissection of the neck, are considered the most common etiologies in the developed world
  • non-surgical trauma, e.g. thoracic duct laceration due to thoracic vertebral fractures

Other less common causes are:


In a neonate:

Radiographic features

Plain radiograph

Increased density of hemithorax due to ipsilateral pleural effusion. Less commonly, chylothorax can be bilateral.


Simple appearing pleural effusion without debris or septations.


Most of the time, it appears as a simple fluid collection of near water density.

Treatment and prognosis

Low output (less than 1000 mL/day) is treated conservatively with a low fat diet. High output usually treated with open or video-assisted ligation. Alternatively, thoracic duct embolization can be performed by an interventional radiologist with a comparable outcome to surgical ligation. Medical therapy with octreotide (somatostatin analog) has been shown to be useful adjunctive therapy in the treatment of postoperative chyle leak following thoracic duct injury .

History and etymology

A chylothorax was first described in the 17 century by Dr. Bartloet. The word chyle is derived from the Greek word “Chylos,” which means juice.

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