What Is Pleural Effusion? - Definition, Causes, Symptoms & Treatment

Instructor: Danielle Haak

Danielle has a PhD in Natural Resource Sciences and a MSc in Biological Sciences

A pleural effusion is an accumulation of fluids in the space between the chest wall and the lungs. Read this lesson to learn why this might happen, what the symptoms are if it does, and how the condition is treated.

About Pleural Effusions

Our bodies require just the right balance of fluids to function properly - imagine how painful it would be if our organs were dry and rubbing against one another as we move. Ouch! However, sometimes imbalances develop, causing there to be too much or too little lubrication, and this is when problems occur.

The lungs and the inside of the chest wall are lined by a membrane called the pleura. Naturally, a small cavity forms in between the chest wall and the lungs called the pleural space. There is usually a small amount of fluid in the pleural space to allow the lungs to move as we breathe, but a pleural effusion occurs when too much fluid accumulates here. This can hinder movement and place extra pressure on the surrounding organs. A pleural effusion may also be referred to as an effusion or a pulmonary effusion.

Diagram showing where pleural effusions form
pleural effusion

Types and Causes of Pleural Effusions

You might not think there's much to know about pleural effusions, but there are two types of categorization doctors might use classify them. The first is an effusion that is transudative or exudative. A transudative effusion is one where the fluid in the pleural space is similar in composition to the normal fluid found there. This type of effusion can be caused by congestive heart failure. An exudative effusion is one where the fluid in the pleural space has excess proteins, blood or indicates there is an infection or inflammation. This type can be caused by conditions like lung cancer or pneumonia.

Pleural effusions can also be classified as uncomplicated or complicated. An uncomplicated effusion is one where the analysis of fluid shows no indication of infection or inflammation, whereas a complicated effusion is one where the fluids show signs of inflammation or infection. This is problematic because the fluid can eventually harden in the pleural space, threatening the lung's ability to function. Complicated effusions need to be drained before permanent lung damage occurs while uncomplicated effusions are unlikely to cause permanent lung damage.

In general, effusions may be caused by congestive heart failure, kidney failure, kidney disease, low albumin levels in the blood, infection, cancer, a pulmonary embolism, cirrhosis of the liver, an injury or trauma, pneumonia, or an autoimmune disease.

Symptoms of Pleural Effusions

Sometimes there aren't any symptoms associated with a pleural effusion, especially if it's small. However, as you can imagine, if the effusion is large, this can cause serious problems. Who wants excess fluids sitting in their chest where all the important stuff is located? When symptoms are present, they can include chest pain, difficult or painful breathing (especially deep breathing), coughing, fever, chills, loss of appetite, and hiccups.

If not treated, pleural effusions can lead to collapsed lungs, scarring, a buildup of pus in the pleural space, blood infections, or extra air in the chest cavity.

Treatment Options

Pleural effusions are typically diagnosed through a physical exam and some type of imaging scan (like an X-ray, CT scan, etc.). Small pleural effusions may go away on their own, but larger ones may need some type of action. If an underlying cause is to blame, treating it may cure the effusion.

A thoracentesis is a procedure where a small tube is inserted into the pleural effusion to manually drain the excess fluid away. However, these are one-time procedures and the tube is removed afterwards. For more serious or chronic cases, a chest tube may be inserted. Again, a tube is inserted to drain the fluid, but it stays put for a longer period of time. For very long-term treatment, a pleural drain may be inserted. This tube stays in place allowing long-term draining.

A thoracentesis procedure is used to manually drain a pleural effusion.
thoracentesis procedure

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