A large chylothorax may lead to breathlessness or a feeling of pressure in the chest, caused by fluid restricting the expansion of the lungs, although large chylothoraces may remain asymptomatic if the chylothorax has accumulated slowly, as the lungs may have had time to become used to the pressure. Fever or chest pain are not usually associated with chylothorax, as chyle does not generate inflammation by itself.On examination, chylothorax may lead to reduced breath sounds on the affected side, associated with a dull sound when the chest is tapped or percussed. In cases of postoperative chylothorax, the first sign may be persistent drainage from intercostal drains. Large chylothoraces may cause signs related to the loss of nutrients, including features of malnutrition or decreased ability to fight infections. Rapidly accumulating chylothoraces can cause a sudden drop in blood volume, leading to low blood pressure. Causes
There are three main types of chylothorax: traumatic, non-traumatic, and idiopathic. Historically the most common form of chylothorax was non-traumatic, but traumatic chylothoraces now represent the majority of cases, with most arising as postoperative complications of surgery. The most common cause of non-traumatic chylothoraces is cancer. Chylothoraces can also be classified as low- or high-output based on the rate of chyle accumulation: low-output chylothoraces accumulate <500 mL of chyle per 24 hours, while high-output chylothoraces accumulate >1000 mL per 24 hours. Non-traumatic
Malignancies are the most frequent cause of non-traumatic chylothorax. Cancers like chronic lymphocytic leukemia, lung cancer, lymphoma, Kaposi sarcoma, metastatic carcinoma or esophageal cancer are potential causes of chylothorax.
Chylotharax after trauma but not after surgery has also been described after central line placement, pacemaker implantation, and embolization of a pulmonary arteriovenous malformation. Blunt trauma to the chest region is another cause of chylothorax, which has occurred after blast injuries and even simple injuries from coughing or sneezing. Mechanism
The main mechanism of chylothorax is the leaking of chyle from the thoracic duct, usually caused by a disturbance affecting the structural integrity of the thoracic duct. For example, placement of a central venous catheter can potentially disrupt drainage of lymph into the subclavian veins, followed by the thoracic duct, resulting in chylothorax. The disturbances cause the pressure in the thoracic duct to increase. Soon, collateral channels form, which eventually drain into the thorax. Trauma affecting the thoracic duct is the most common disturbing mechanism. Whether a chylothorax occurs in the left or right pleural space is a consequence of the thoracic ducts anatomic location in the body and depends on the level where the duct was injured. If the thoracic duct is injured above the fifth thoracic vertebra, then a left-sided chylothorax results. Conversely, a thoracic duct injury below that level will lead to the formation of a right-sided chylothorax. Chylothoraces most commonly occur in the right pleural space (50% of cases). Left-sided and bilateral chylothoraces are less common and occur in 33% and 17% of cases, respectively.In the case of cancer, invasion into the thoracic duct or collateral lymph channels can obstruct lymph.