A 57-year-old man comes to the physician with 3 months of cough, night sweats, and subjective fevers. He has been feeling "run down." The patient emigrated from India 26 years ago and has not travelled recently. He had a negative tuberculin skin test 6 months ago performed at work.
Lung examination is significant for reduced breath sounds with dullness to percussion on the left.
Chest imaging reveals a moderate left-sided pleural effusion with bulky mediastinal lymphadenopathy. A thoracentesis shows turbid white fluid. Laboratory results are as follows:

Which of the following tests performed on pleural fluid would help identify the cause of the effusion?

Question

A 57-year-old man comes to the physician with 3 months of cough, night sweats, and subjective fevers.  He has been feeling "run down."  The patient emigrated from India 26 years ago and has not travelled recently.  He had a negative tuberculin skin test 6 months ago performed at work.
Lung examination is significant for reduced breath sounds with dullness to percussion on the left.
Chest imaging reveals a moderate left-sided pleural effusion with bulky mediastinal lymphadenopathy.  A thoracentesis shows turbid white fluid.  Laboratory results are as follows:

Which of the following tests performed on pleural fluid would help identify the cause of the effusion?

Quizplus · Accepted Answer

11ec193a_98e8_6fe4_853d_994b896979a3_MD0002_00 Constitutional "B" symptoms and mediastinal lymphadenopathy suggest lymphoma in this patient. Malignancy itself can cause an exudative pleural effusion, but the characteristic "milky white" appearance is typically seen with chylothorax. Triglycerides >110 mg/dL strongly support the diagnosis. Chylothorax is a relatively rare cause of pleural effusion, usually due to traumatic or non-traumatic disruption of the thoracic duct. The most common non-traumatic cause is thoracic duct obstruction due to malignancy, sarcoidosis, or retrosternal goiter, and infections such as tuberculosis and filariasis. Traumatic disruption most commonly occurs in central venous catheter placement (subclavian approach) and esophageal surgery. When associated with cirrhosis, congestive heart failure, or nephritic syndrome, the chylothorax may be transudative. (Choice A) Amylase levels are high in patients with esophageal rupture or pancreatitis. (Choice B) Bacterial culture is not likely to be helpful when the neutrophil count is low. Acid-fast staining and culture may be useful in lymphocytic effusions if tuberculosis is suspected. (Choice C) Brain natriuretic peptide level is frequently elevated (>115 pg/mL) in pleural effusions secondary to congestive heart failure. However, pleural fluid testing offers little benefit over serum testing. (Choice D) Both cholesterol and triglycerides often give the effusion a milky-white appearance. Cholesterol effusions (pseudo-chylothorax) occur when an exudative effusion remains in the pleural space chronically, allowing it to become enriched with cholesterol. These most commonly occur in tuberculous or rheumatoid pleurisy. Educational objective: A chylothorax is a rare effusion with a classic milky-white appearance that is caused by traumatic or non-traumatic thoracic duct obstruction. Bulky lymphadenopathy from lymphoma is an important etiology. __________ References: Pleural effusions. (http://www.ncbi.nlm.nih.gov/pubmed/22032427) Getting the most from pleural fluid analysis. (http://www.ncbi.nlm.nih.gov/pubmed/22059482) Chylothorax: etiology, diagnosis and therapeutic options. (http://www.ncbi.nlm.nih.gov/pubmed/19766473)

A 57-Year-Old Man Comes to the Physician with 3 Months