Chylothorax

What chylothorax is

After a meal, fats absorbed in the gut are packaged into tiny particles (chylomicrons) and carried in lymph called chyle. Chyle flows up through the thoracic duct, which runs through the chest alongside the esophagus and aorta and empties into a large vein at the base of the neck. Up to 2 to 4 liters of chyle pass through it each day, carrying fats, proteins, fat-soluble vitamins and white blood cells (lymphocytes).

If the duct is damaged or blocked, chyle leaks into the pleural space, forming a type of pleural effusion. Because so much fluid flows through the duct, effusions can build up quickly.

Causes

Traumatic (about half of cases)

• Surgery: esophagectomy, lung cancer surgery, heart surgery (especially in children with congenital heart disease), neck dissection, and spine surgery
• Chest trauma: blunt or penetrating injury, sometimes from severe coughing or vomiting
• Procedures: central line placement in the neck

Non-traumatic

• Cancer: lymphoma is the most common non-traumatic cause; also lung cancer and metastatic cancers
• Lymphatic disorders: lymphangioleiomyomatosis (in women), lymphatic malformations, generalized lymphatic anomaly, Gorham-Stout disease
• Blockage of the central veins: thrombosis of the superior vena cava or subclavian vein
• Infections: tuberculosis, filariasis (in some countries)
• Congenital chylothorax: in newborns, often associated with Down syndrome, Noonan syndrome or Turner syndrome
• Other: sarcoidosis, cirrhosis, heart failure, amyloidosis

Symptoms

Chylothorax is usually painless, because chyle does not irritate the pleura much. Symptoms depend on the amount of fluid:

• shortness of breath, especially on exertion
• chest heaviness or discomfort
• cough
• fatigue
• in long-lasting cases: weight loss, muscle wasting, swelling and frequent infections

Diagnosis

1. Chest X-ray, ultrasound or CT: show fluid around the lung. CT may reveal a cause such as enlarged lymph nodes.
2. Thoracentesis: a needle removes fluid for analysis. Chyle typically looks milky white, although it can be clear if the person has not been eating.
3. Fluid tests: - triglycerides above 110 mg/dL strongly suggest chylothorax - triglycerides below 50 mg/dL make it unlikely - chylomicrons in the fluid confirm it in borderline cases - lymphocyte-rich cell count
4. Finding the leak: lymphangiography or MR lymphangiography to map the thoracic duct, and to guide treatment.
5. Finding the cause: CT scans, lymph node biopsy for suspected lymphoma.

A pseudochylothorax (cholesterol effusion) can look similar but has high cholesterol rather than triglycerides and arises from long-standing effusions, such as old tuberculosis or rheumatoid arthritis.

Treatment

Conservative treatment

Often tried first, especially after surgery:

• Drainage: a chest tube or repeated thoracentesis relieves breathlessness and measures daily output.
• Dietary changes: a very low long-chain fat diet with medium-chain triglyceride (MCT) oil, which is absorbed directly into the blood and bypasses the lymph system, reducing chyle flow.
• Nothing by mouth with IV nutrition (TPN): for high-output leaks.
• Octreotide or somatostatin: reduce lymph production in some people.
• Nutrition and fluid replacement: protein, vitamins and electrolytes.

Procedures

• Thoracic duct embolization: an interventional radiologist blocks the leaking duct through a needle in the abdomen, guided by lymphangiography. It is minimally invasive and effective in many cases.
• Surgical thoracic duct ligation: tying off the duct, usually by video-assisted surgery, when output stays high (for example over 1 liter a day) or the leak persists beyond 1 to 2 weeks.
• Pleurodesis: sealing the pleural space with talc or other agents.
• Indwelling pleural catheter or pleuroperitoneal shunt for recurrent malignant chylothorax.

Treating the cause

Lymphoma-related chylothorax often resolves with chemotherapy or radiotherapy. Lymphangioleiomyomatosis may respond to sirolimus.

Complications

• malnutrition and weight loss from losing fats and protein
• immune suppression from loss of lymphocytes and antibodies, leading to infections
• dehydration and electrolyte imbalance
• trapped lung from long-standing fluid

Frequently asked questions

What is chylothorax?

Chylothorax is a collection of chyle, the milky, fat-rich lymph fluid from the gut, in the space around a lung. It occurs when the thoracic duct, the main lymph channel in the chest, is damaged by surgery or injury, or blocked by cancer or other conditions.

What causes chylothorax?

The most common cause is injury to the thoracic duct during chest or neck surgery, such as esophagus or heart operations. Non-surgical causes include lymphoma and other cancers, lymphatic disorders, blood clots in the central veins, infections and congenital conditions in newborns.

How is chylothorax diagnosed?

Doctors drain a sample of fluid from the chest. Milky fluid with triglycerides above 110 mg/dL, or chylomicrons on testing, confirms chylothorax. Imaging such as CT and lymphangiography helps locate the leak and find the cause.

How is chylothorax treated?

Treatment starts with draining the fluid and a low-fat diet using MCT oil, or IV nutrition, sometimes with octreotide. If the leak continues, the thoracic duct is blocked by embolization or tied off surgically. Underlying causes such as lymphoma are treated directly.

Can chylothorax heal on its own?

Many postoperative leaks close within 1 to 2 weeks with drainage and dietary changes. High-output or persistent leaks usually need embolization or surgery. Chylothorax from cancer typically improves only when the cancer is treated.