Chylothorax and Haemothorax
On this page
Direct answer
Chylothorax is milky pleural effusion from leakage of thoracic duct lymph, confirmed by a pleural triglyceride level above 110 mg/dL. Haemothorax is blood in the pleural space, defined by a pleural haematocrit above half the blood haematocrit. Malignancy and thoracic surgery are the main causes of chylothorax, while trauma is the commonest cause of haemothorax. Both are managed with pleural drainage, and surgery follows large or persistent output.
What you must remember
- Chylothorax test: pleural triglyceride above 110 mg/dL confirms chyle, with chylomicrons on lipoprotein analysis giving supporting evidence.
- Pseudochylothorax: milky fluid from cholesterol, with high cholesterol and low triglycerides, typically seen in tuberculous and rheumatoid effusions.
- Chylothorax causes: lymphoma and other malignancy, thoracic and oesophageal surgery, trauma, lymphatic filariasis in endemic regions and congenital disease.
- First-line chylothorax care: a low long-chain fat diet with medium-chain triglycerides, which bypass the thoracic duct, and drainage of the effusion.
- Escalation: octreotide to reduce lymph flow, then pleurodesis or thoracic duct ligation when conservative care fails.
- Haemothorax definition: pleural fluid haematocrit above 50 percent of the blood haematocrit.
- Haemothorax causes: trauma, the commonest, along with iatrogenic injury from central lines or procedures, ruptured aortic aneurysm, and anticoagulation or bleeding disorders.
- Surgical threshold: initial drainage of about 1500 mL, or continuing output above 200 mL per hour over several hours, calls for thoracotomy.
Two bloody and milky effusions compared
Both conditions present as a large pleural effusion whose colour and biochemistry decide the diagnosis and the treatment. Early identification matters, because the wrong first step, such as a high-fat diet or a delayed drain, worsens the outcome.
| Feature | Chylothorax | Haemothorax |
|---|---|---|
| Fluid appearance | Milky white | Red or dark blood |
| Key test | Triglycerides above 110 mg/dL | Haematocrit above 50 percent of blood |
| Commonest setting | Malignancy and thoracic surgery | Blunt or penetrating trauma |
| First step | Low-fat diet with medium-chain fat and drainage | Chest drain and resuscitation |
| Escalation | Octreotide, then pleurodesis or duct ligation | Thoracotomy for large or continuing output |
| Pitfall | Pseudochylothorax has low triglycerides | Retained clot leads to empyema |
Milky fluid is never labelled chylothorax by appearance alone, because triglyceride testing separates it from pseudochylothorax. Blood-stained fluid with a high haematocrit demands drainage first, whereas chyle is managed first by diet and drainage, with octreotide reserved for failure.
Where the exam tries to catch you
Pleural colour is a clue, and the biochemistry gives the answer.
- Trap: labelling milky fluid as chylothorax without a triglyceride test Correct: pseudochylothorax is also milky, with high cholesterol and low triglycerides, so the test is decisive.
- Trap: feeding a chylothorax patient a high-fat diet Correct: long-chain fat increases lymph flow into the leak, whereas medium-chain fat is absorbed directly into the portal circulation.
- Trap: waiting on a haemothorax with ongoing bleeding Correct: large initial or persistent output needs early thoracotomy, because ongoing bleeding is the threat.
Frequently asked questions
What pleural triglyceride level confirms chylothorax?
A pleural triglyceride level above 110 mg/dL confirms chylothorax in a milky effusion. Chylomicrons on lipoprotein analysis give supporting evidence where that test is available.
How does pseudochylothorax differ from chylothorax?
Pseudochylothorax has high cholesterol with low triglycerides and cholesterol crystals, whereas chylothorax has high triglycerides from thoracic duct lymph. Tuberculosis and rheumatoid pleurisy are the classic causes of pseudochylothorax.
When is surgery needed for haemothorax?
Surgery is needed when initial chest drain output is about 1500 mL or when bleeding continues above 200 mL per hour for several hours. Retained clot that persists after drainage is also an indication for video-assisted thoracoscopic evacuation.
Why is a medium-chain triglyceride diet used in chylothorax?
Medium-chain triglycerides are absorbed directly into the portal circulation and bypass the thoracic duct lymph. This reduces lymph flow into the leak and is combined with a low long-chain fat diet in the usual management of chylothorax.