Clinical Definition

Pleural effusion is an accumulation of excess fluid between the pulmonary pleural layers. A pleural effusion can occur without symptoms; alternatively there may be symptoms including chest pain, nonproductive cough and dyspnea. This excess fluid can be described as transudative (watery) or exudative (protein-rich), which can help in determining the etiology.

In Our Own Words

It’s normal to have a little bit of fluid outside the lungs but within the chest, to lubricate and help lung tissue expand and contract. A pleural effusion, however, is an abnormal accumulation of fluid in this space around the lungs. Infections, blood clots, and other conditions such as cancer may cause a pleural effusion. The fluid can often be seen on a chest X-ray, and doctors can take a sample using a needle, in a procedure known as thoracentesis.

A more watery (transudative) effusion is commonly associated with conditions such as heart failure, liver cirrhosis, or after open-heart surgery. Thicker, protein-rich (exudative) effusions, on the other hand, are more commonly associated with blood clots in the lung, cancer, pneumonia, kidney disease or other sources of inflammation.