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JAMA Patient Page
January 21, 2009

Pleural Effusion

JAMA. 2009;301(3):344. doi:10.1001/jama.301.3.344

When an abnormal amount of fluid accumulates in the space between the 2 layers of the pleura (the membrane that lines the surface of the lungs), it is called a pleural effusion. It is estimated that 1 million people in the United States develop a pleural effusion each year. About 20% to 60% of the people who develop pneumonia have a pleural effusion. A pleural effusion can also occur due to an extrapulmonary (outside the lungs) cause. Treatment depends on the underlying cause. The January 21, 2009, issue of JAMA includes an article about diagnosing pleural effusions.


  • Dyspnea (shortness of breath)

  • Cough

  • Chest pain

Causes of pleural effusions

  • Congestive heart failure (ineffective pumping of blood through the circulatory system due to enlargement and weakening of the heart muscle) is the most common cause of pleural effusion.

  • Pneumonia is a common lung infection and may result in pleural effusion.

  • Pulmonary emboli (a blood clot that breaks off and travels through the bloodstream where it becomes stuck and blocks the circulation)

  • Malignancy (cancer) of the lungs can result in pleural effusions. Metastasis (cancer that has spread from one organ or body part to another) to the lung can also cause pleural effusions.

  • Cirrhosis (liver disease with loss of function and scarring of the tissue within the liver) commonly causes ascites (fluid collection in the abdomen) and may cause a pleural effusion.

Diagnosing pleural effusions

  • Physical examination of the lungs includes using visual inspection to look for asymmetry of chest wall expansion with breathing, auscultatory (listening) and tactile (feeling) assessment of air flow, and percussion (gentle tapping with the fingertips) to detect differences in sound transmission from the lungs through the chest wall.

  • X-ray examination of the chest with the patient in an upright position and in a lateral decubitus (lying down) position on the side where the effusion is located to get a visual estimate of the amount of fluid present

  • Ultrasound can detect small pleural effusions by measuring the difference in the sound waves as they travel through the air in the lungs compared with the fluid created by an effusion.

  • CT scan is a radiographic procedure that can be used to image the lungs and detect the presence of pleural effusions around them.

  • Thoracentesis uses a thin needle inserted into the chest cavity to withdraw a sample of the fluid for laboratory analysis.


  • Treating bacterial pneumonia with antibiotics usually resolves pleural effusion.

  • Treating congestive heart failure with diuretics (medication that removes excess fluid from the circulation) and other medications to support the heart muscle helps to resolve an associated pleural effusion.

  • When the pleural effusion is large, thoracentesis may be used to remove some of the fluid for symptom relief while the underlying cause is being treated.

For more information

Inform yourself

To find this and other JAMA Patient Pages, go to the Patient Page link on JAMA's Web site at http://www.jama.com. Many are available in English and Spanish. A Patient Page on lung cancer was published in the March 7, 2007, issue, one on pulmonary embolism in the December 3, 2003, issue, and one on heart failure in the June 13, 2007, issue.

Source: American Lung Association

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