What Is a Pleural Effusion?

Medically Reviewed by Melinda Ratini, MS, DO on April 21, 2023
4 min read

pleural effusion is an unusual amount of fluid around the lung. Many medical conditions can lead to it, so even though your pleural effusion may have to be drained, your doctor likely will target the treatment at whatever caused it.

The pleura is a thin membrane that lines the surface of your lungs and the inside of your chest wall. When you have a pleural effusion, fluid builds up in the space between the layers of your pleura.

Normally, only teaspoons of watery fluid are in the pleural space, which allows your lungs to move smoothly in your chest cavity when you breathe.

A wide range of things can cause a pleural effusion. Some of the more common ones are:

Leaking from other organs. This usually happens if you have congestive heart failure, when  your heart doesn't pump blood to your body properly. But it can also come from liver or kidney disease, when fluid builds up in your body and leaks into the pleural space.

Cancer. Usually lung cancer is the problem, but other cancers that have spread to the lung or pleura can cause it, too.

Infections. Some illnesses that lead to pleural effusion are pneumonia or tuberculosis.

Autoimmune conditions. Lupus or rheumatoid arthritis are some diseases that can cause it.

Pulmonary embolism. This is a blockage in an artery in one of your lungs, and it can lead to pleural effusion.

You might not have any. You're more likely to have symptoms when a pleural effusion is moderate or large-sized, or if there is also inflammation.

If you do have symptoms, they may include:

  • Shortness of breath
  • Chest pain, especially when breathing in deeply (This is called pleurisy or pleuritic pain.)
  • Fever
  • Cough

Your doctor will talk to you about your symptoms and give you a physical exam. They'll tap on your chest and listen with a stethoscope.

To confirm you have a pleural effusion, you'll need to get imaging tests such as:

Chest X-ray. Pleural effusions appear white on X-rays, while air space looks black. If a pleural effusion is likely, you may get more X-ray films while you lie on your side. These can show if the fluid flows freely within the pleural space.

Computed tomography (CT scan). A CT scanner takes many X-rays quickly, and a computer constructs images of the entire chest -- inside and out. CT scans show more detail than chest X-rays do.

Ultrasound. A probe on your chest will create images of the inside of your body, which show up on a video screen. Your doctor may use the ultrasound to locate the fluid so they can get a sample for analysis.

Also, your doctor might do a procedure called thoracentesis. They'll take a little bit of the fluid to test. To do this, they insert a needle and a tube called a catheter between your ribs, into the pleural space.

You may hear your doctor use the terms "transudative" and "exudative" to describe the two main types of pleural effusions.

Transudative. This pleural effusion fluid is similar to the fluid you normally have in your pleural space. It forms from liquid leaking across normal pleura. This type rarely needs to be drained unless it's very large. Congestive heart failure is the most common cause of this type.

Exudative. This forms from extra liquid, protein, blood, inflammatory cells or sometimes bacteria that leak across damaged blood vessels into the pleura. You may need to get it drained, depending on its size and how much inflammation there is. The causes of this type include pneumonia and lung cancer.

Your doctor may need to treat only the medical condition that caused the pleural effusion. You would get antibiotics for pneumonia, for instance, or diuretics for congestive heart failure.

Large, infected, or inflamed pleural effusions often need to get drained to help you feel better and prevent more problems.

Procedures for treating pleural effusions include:

Thoracentesis. If the effusion is large, your doctor may take more fluid than they need for testing, just to ease your symptoms.

Tube thoracostomy (chest tube). Your doctor makes a small cut in your chest wall and puts a plastic tube into your pleural space for several days.

Pleural drain. If your pleural effusions keep coming back, your doctor may put a long-term catheter through your skin into the pleural space. You can then drain the pleural effusion at home. Your doctor will tell you how and when to do that.

Pleurodesis. Your doctor injects an irritating substance (such as talc or doxycycline) through a chest tube into the pleural space. The substance inflames the pleura and chest wall, which then bind tightly to each other as they heal. Pleurodesis can prevent pleural effusions from coming back in many cases.

Pleural decortication. Surgeons can operate inside the pleural space, removing potentially dangerous inflammation and unhealthy tissue. To do this, your surgeon may make small cuts (thoracoscopy) or a large one (thoracotomy).