Chylothorax is a medical condition characterized by the abnormal buildup of a specific lymphatic fluid, known as chyle, within the chest cavity. This rare condition occurs when the primary vessel that transports this fluid becomes damaged or obstructed, allowing the fluid to leak into the space surrounding the lungs. Recognizing and treating this fluid accumulation is important, as it can lead to breathing difficulties and significant nutritional loss.
Understanding Chyle and the Pleural Space
Chyle is a milky-white or pale yellow bodily fluid that forms in the small intestine after a person eats a meal containing fat. It is essentially lymph that is rich in digested fats, specifically long-chain triglycerides, which are packaged into particles called chylomicrons. Chyle also carries proteins, immune cells, and fat-soluble vitamins, making its loss a concern for the body’s overall health.
This nutrient-rich fluid is collected by specialized lymphatic vessels in the intestine and travels upward through the largest lymphatic vessel in the body, the thoracic duct. The thoracic duct runs vertically through the chest, collecting lymph from the lower body and much of the upper left side before emptying into the major veins near the neck. If the thoracic duct is disrupted, the chyle bypasses the bloodstream and instead drains into the pleural space.
The pleural space is a thin, potential area located between two membranes that line the lungs and the inner chest wall. Normally, this space contains only a small amount of clear fluid that acts as a lubricant, allowing the lungs to expand and contract smoothly during breathing. When chyle accumulates in this space—a condition known as chylothorax—it exerts pressure on the lungs, which interferes with normal respiratory mechanics.
Common Causes and Risk Factors
A disruption of the thoracic duct that causes chylothorax is broadly classified as either traumatic or non-traumatic. The most frequent cause in developed countries is iatrogenic trauma. This complication is seen most often following complex operations on the chest, such as cardiac surgery, especially in children, or procedures involving the esophagus or thoracic aorta, due to the close anatomical relationship of these structures to the duct.
Non-surgical trauma, such as blunt force injury to the chest or spine, can also cause the thoracic duct to rupture, though this is less common. When the cause is not related to trauma, the chylothorax is termed non-traumatic, and it is usually due to an underlying medical condition. Malignancy represents the most common non-traumatic cause, with cancers like lymphoma accounting for a large percentage of these cases.
In these instances, a tumor may either directly invade and damage the lymphatic system or create an obstruction that increases pressure within the duct until it leaks. Congenital chylothorax is a rare subset seen in newborns, often associated with lymphatic malformations or certain genetic syndromes. Other, less frequent causes include infectious diseases like tuberculosis, or conditions that cause elevated central venous pressure.
Recognizing the Signs and Diagnostic Procedures
The symptoms of chylothorax are often related to the speed and volume of fluid accumulation, which compresses the lung. The most common sign is shortness of breath, particularly with physical activity. Patients may also experience a dry cough, chest discomfort, or a feeling of heaviness in the chest.
Initial imaging usually involves a chest X-ray to confirm the presence of fluid surrounding the lung, which appears as a pleural effusion. A computed tomography (CT) scan is often used next to better visualize the extent of the fluid and to help identify potential underlying causes, such as a mass or lymphadenopathy. The definitive diagnosis, however, is made by performing a thoracentesis, a procedure where a needle is inserted into the chest to withdraw a sample of the fluid.
Laboratory analysis of this aspirated fluid confirms the diagnosis. Confirmation relies on measuring the triglyceride level in the pleural fluid; a concentration greater than 110 mg/dL is considered diagnostic for chylothorax. The presence of chylomicrons provides conclusive evidence.
Approaches to Management
The primary goals of chylothorax management are to drain the accumulated fluid, address the nutritional deficiencies caused by the fluid loss, and ultimately stop the leak. Initial treatment is often conservative and involves placing a chest tube to continuously drain the chyle and relieve pressure on the lung. Nutritional management is also essential and typically involves a highly restricted low-fat diet, which is supplemented with medium-chain triglycerides (MCTs).
MCTs are absorbed directly into the bloodstream through the portal vein, bypassing the lymphatic system and the thoracic duct, which helps to reduce the volume of chyle produced. In cases of high-volume leaks or persistent drainage, total parenteral nutrition (TPN) may be used to provide all necessary nutrients intravenously, completely resting the digestive and lymphatic systems. A synthetic drug called octreotide may also be administered to help reduce the flow of lymph and promote the closure of the leak.
If these conservative measures fail to resolve the chylothorax after one to two weeks, or if the chyle output remains high, interventional or surgical options are pursued. Minimally invasive procedures like thoracic duct embolization (TDE) can be performed by an interventional radiologist to locate the precise site of the leak and seal it off using a specialized glue. If TDE is not technically feasible or unsuccessful, a surgeon may perform a thoracic duct ligation, which involves surgically tying off the duct to halt the chyle flow. Another surgical option, pleurodesis, involves introducing an irritant into the pleural space to fuse the lung and chest wall linings together, thereby eliminating the space where fluid can accumulate.