The chylothorax shows up on the images and identifies the source any leak in the thoracic duct.Another, more commonly used type of lymphogram is nuclear lymphoscintigraphy; this procedure requires human pentetic acid labeled Tc99m to be injected into the subcutaneous lesions of both sides of the dorsum of the foot. Then two images, anterior and posterior, are obtained using gamma-ray cameras. This test can be used with an integrated low-dose CT-scan with photon emission to get images that are more precise. Once pleural effusion is detected, a thoracentesis is recommended.The fluid of a chylothorax may appear milky, serous or serosanguineous. If the appearance of the fluid is not milky, that does not exclude a chylothorax from consideration. Since chyle is rich in triglycerides, a pleural effusion that is rich in triglycerides (>110 mg/dL) confirms the presence of a chylothorax; a pleural effusion that is low in triglyceride content (<50 mg/dL) virtually excludes the diagnosis. If a pleural effusion contains triglycerides between 50 and 110 mg/dL, analysis of the lipoprotein content of the pleural effusion to evaluate for chylomicrons is recommended. If that procedure detects chylomicrons in the fluid, that confirms a chylothorax. Chylothoraces are typically exudative and often contain a high number of lymphocytes and have low levels of the enzyme lactate dehydrogenase (LDH). However, atypical chylothoraces can occur and are transudative in 14% of cases. A milky appearance of pleural fluid is insufficient to confirm the diagnosis of chylothorax as pseudochylothoraces and empyemas can mimic this appearance.
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.