page_title: Chylothorax
section_title: Diagnosis
hierarchical_section_title: Chylothorax / Diagnosis
caption_attribution_description: English: Extensive chylothorax caused by leakage from the thoracic duct.
context_page_description: A chylothorax is an accumulation of lymphatic fluid in the space surrounding the lung. Lymph formed in the digestive system is called chyle and accumulates in the pleural space due to either disruption or obstruction of the thoracic duct. In people on a normal diet, this fluid collection can sometimes be identified by its turbid, milky white appearance, since chyle contains triglycerides. It is important to distinguish a chylothorax from a pseudochylothorax, which has a similar appearance, but is caused by more chronic inflammatory processes, and requires a different treatment.
  Chylothorax is a rare but serious condition. It results from leakage of lymph fluid from the thoracic duct or one of its tributaries. There are many treatments, both surgical and conservative. About 2-3% of all fluid collections surrounding the lungs are chylothoraces.
context_section_description: Chest X-rays can detect a chylothorax. It appears as a dense, homogenous area that obscures the costophrenic and cardiophrenic angles. Ultrasounds can also detect a chylothorax, which appears as an echoic region that is isodense with no septation or loculation. However, neither a normal chest x-ray nor an ultrasound can differentiate a chylothorax from any other type of pleural effusion.
  The cisterna chyli can be found in a thoracic MRI, making it possible to confirm chylothorax. However, MRI is not the ideal method to scan the thorax, and so it is rarely used. Another diagnostic technique is conventional lymphangiography. It is rarely used since there are equally sensitive yet less invasive techniques available to identify a chylothorax. Lymphangiography procedures use the contrast dye agent lipiodol, which is injected into the lymphatic vessels. 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 50-110 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. Conversely, the absence of a milky appearance does not mean a chylothorax is not present as they may instead appear serous or bloody.
caption: CT scan showing extensive chylothorax caused by leakage from the thoracic duct
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