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Chylothorax — lymph leak into the pleural space
Chylothorax is a collection of lymph (chyle) in the pleural space from injury to the thoracic duct — usually after chest surgery or from lymphoma; the diagnosis is a fluid triglyceride above 110 mg/dL or chylomicrons, treatment begins with drainage and reduced lymph flow, and when output is high and prolonged it moves to ligation or embolisation of the thoracic duct.
Why it matters in the exam
Anatomy explains the side of the effusion: the thoracic duct begins at the cisterna chyli at the level of L2, ascends on the right side of the chest between the aorta and the azygos vein, crosses to the left at T4–T6 and drains into the junction of the left subclavian and internal jugular veins. So a low injury (below the crossing) causes a right chylothorax, and a high one — a left. Causes are traumatic (mainly operations — oesophagectomy, lung resection with node dissection, cardiac and neck surgery) and non-traumatic, in which lymphoma is the leading cause. The fluid is milky, but in a fasting patient it may be clear, so the classic sign sometimes appears only after feeding resumes.
Diagnosis: triglycerides above 110 mg/dL strongly support it; a value below 50 mg/dL almost excludes it; in the intermediate range chylomicrons are tested. It must be distinguished from "pseudochylothorax" — a chronic effusion (tuberculosis, rheumatoid arthritis) with cholesterol above 200 mg/dL and cholesterol crystals, unrelated to the thoracic duct. Conservative treatment: drainage, fasting with parenteral nutrition or a low-fat diet with MCT (absorbed directly into the portal vein, bypassing the lymph), and sometimes octreotide. If output stays high — above 1 litre per day after about 5 days — or there is nutritional and immune depletion (falling albumin and lymphocytes), thoracic duct ligation is done in the lower right chest above the diaphragm, or percutaneous duct embolisation guided by lymphangiography. In lymphoma-related chylothorax the main treatment is of the lymphoma.
Prolonged loss of chyle causes malnutrition, fluid and electrolyte depletion and immunosuppression, so conservative treatment must not continue indefinitely.
Key points
- Triglycerides above 110 mg/dL.
- After surgery or from lymphoma.
- Low — right, high — left.
- Drainage, MCT or fasting, octreotide.
- Prolonged high output — ligation or embolisation.
Summary table
| Feature | Chylothorax | Pseudochylothorax |
|---|---|---|
| Origin | Thoracic duct injury | Old chronic effusion |
| Laboratory | Triglycerides above 110 mg/dL, chylomicrons | Cholesterol above 200 mg/dL, cholesterol crystals |
| Causes | Chest surgery, lymphoma, trauma | Tuberculosis, rheumatoid arthritis |
| Treatment | Drainage, MCT or fasting, ligation or embolisation | Treat the cause, decortication as needed |
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Sources
- BTS Guideline for Pleural Disease, 2023 — Chylothorax and pseudochylothorax
- Shields' General Thoracic Surgery, 8th edition (2019) — Chylothorax and the thoracic duct
- Sabiston Textbook of Surgery, 21st edition (2022) — Chest wall, pleura and mediastinum
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.