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Cloudy Pleural Fluid on Thoracentesis


Am Fam Physician. 2020 Sep 1;102(5):307-308.

A 68-year-old man with chronic obstructive pulmonary disease from long-term tobacco use presented to the emergency department with worsening shortness of breath over the previous week. Simple tasks such as walking to the mailbox or up a flight of stairs exacerbated his dyspnea. His chronic obstructive pulmonary disease was managed with albuterol and tiotropium (Spiriva) inhalers, and he had never been hospitalized for an exacerbation.

His medical history was significant for longstanding hypertension and hyperlipidemia and a recent diagnosis of a nonobstructing lung cancer. His additional medications included amlodipine (Norvasc) and atorvastatin (Lipitor). The patient was retired, drank one or two alcoholic beverages daily, and had a 60-pack-year smoking history. He did not use illicit drugs.

His vital signs were significant for blood pressure of 155/75 mm Hg, pulse of 95 beats per minute, and respiratory rate of 24 breaths per minute. His oxygen saturation level was 85% on room air but improved to 94% on 2 L of oxygen. Physical examination revealed diminished breath sounds and dullness to percussion at the right base but was otherwise normal. Chest radiography confirmed a large right-sided pleural effusion. Pleural fluid was opaque on thoracentesis (Figure 1).




Based on the patient's physical examination and history findings, which one of the following is the most likely diagnosis?

A. Chylothorax.

B. Congestive heart failure.

C. Parapneumonic effusion.

D. Pseudochylothorax.


The answer is A: chylothorax. Chylothorax develops when the thoracic duct is damaged, causing large amounts of chyle containing triglycerides/chylomicrons, T lymphocytes, electrolytes, proteins, and fat-soluble vitamins to flow into the pleural space. Chylothorax appears as milky or cloudy pleural fluid.1,2 When evaluating pleural fluid, Light criteria can be used to distinguish between an exudate and a transudate. Fluid is exudative if pleural fluid protein divided by serum protein is greater than 0.5; pleural fluid lactate dehydrogenase (LDH) divided by serum LDH is greater than 0.6; or pleural fluid LDH is more than two-thirds the upper limit of normal for serum LDH.3

Malignancy, such as lymphoma, is the leading cause of chylothorax.4,5 Surgical injuries, nonmalignant masses,

Address correspondence to Justin Bailey, MD, FAAFP, at Reprints are not available from the authors.

Author disclosure: No relevant financial affiliations.


show all references

1. Pleural effusion. DynaMed. Updated November 30, 2018. Accessed November 24, 2019.

2. Saguil A, Wyrick K, Hallgren J. Diagnostic approach to pleural effusion. Am Fam Physician. 2014;90(2):99–104. Accessed July 9, 2020.

3. Hooper C, Lee YCG, Maskell N. Investigation of a unilateral pleural effusion in adults: British Thoracic Society pleural disease guideline 2010. Thorax. 2010;65(suppl 2):ii4–ii17.

4. Heffner JE. Diagnostic evaluation of a pleural effusion in adults: initial testing. UpToDate. Updated March 9, 2020. Accessed November 24, 2019.

5. Heffner JE. Management of malignant pleural effusions. UpToDate. Updated May 5, 2020. Accessed November 24, 2019.

6. Chakko S. Pleural effusion in congestive heart failure. Chest. 1990;98(3):521–522.

7. Parapneumonic effusion and empyema in adults. DynaMed. Updated November 30, 2018. Accessed November 24, 2019.

8. Lama A, Ferreiro L, Toubes ME, et al. Characteristics of patients with pseudochylothorax—a systematic review. J Thorac Dis. 2016;8(8):2093–2101.

This series is coordinated by John E. Delzell Jr., MD, MSPH, associate medical editor.

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