Pleural effusion is caused by many disorders and can potentially be life-threatening.

Symptoms may resemble other respiratory problems, and diagnosis and treatment depend on the underlying cause.

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The buildup of fluid between the chest cavity and the lungs may be caused by a disease or disorder.
Image credit: James Heilman, MD, n.d.

A pleural effusion is a buildup of fluid in the space between the lungs and chest cavity, called the pleural space. It is also commonly called water on the lung.

Thin membranes called pleura line both the lung and chest cavity in the body.

In healthy lungs, these membranes keep a small amount of liquid between the lungs and chest to prevent friction as the lungs expand and contract during breathing.

Someone who has a pleural effusion has too much liquid in the pleural space.

People experiencing a pleural effusion must seek immediate medical attention, as it can be life-threatening if it is left untreated.

Pleural effusion is always a secondary disorder, meaning that it is caused by something else. Many things can cause the pleura to create more liquid than normal.

Some of the most common causes of pleural effusion are other diseases and disorders, including:

  • Liver or kidney disease: Diseases such as cirrhosis may cause fluid to build up in the body and leak into the chest.
  • Congestive heart failure: Failure of the heart to pump blood properly can cause a buildup of liquid in the chest.
  • Autoimmune disorders: Disorders such as lupus or rheumatoid arthritis may target the lungs and create problems with the pleura.
  • Infections: Respiratory infections such as tuberculosis and pneumonia could progress and cause water on the lung.
  • Pulmonary embolism: A blockage in the arteries of the lung caused by a blood clot can cause the pleura to create too much liquid.
  • Cancer: Typically lung cancer, though any cancer which has progressed to the lungs or pleura can be the cause.

Complications from certain medical procedures can also trigger a pleural effusion as well. Open-heart surgery is a common cause, but any surgery involving the chest may also increase the risk of a pleural effusion.

Physical symptoms of a pleural effusion commonly show up as liquid fills the chest cavity. These symptoms include:

  • dry, unproductive cough
  • difficulty breathing, especially when lying down
  • fever
  • chest pain
  • shortness of breath
  • inability to take deep breaths or pain caused by taking deep breaths

A person who often experiences hiccups or a pattern of hiccups that do not go away may also be experiencing pleural effusion.

Some people do not experience symptoms of pleural effusion at all. They usually find out about the liquid in their lungs after a physical exam for an unrelated condition.

The signs and symptoms of pleural effusion may also be confused with other lung disorders. People should schedule an appointment with their doctor immediately if they experience these symptoms.

Below is a 3-D model of pleural effusion, which is fully interactive.

Explore the model using your mouse pad or touchscreen to understand more about pleural effusion.

Diagnosing pleural effusion is not straightforward as many disorders cause similar symptoms. In the first instance, doctors will give the person a physical exam.

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An initial pleural effusion diagnosis may be difficult as the symptoms are similar to other disorders. A CT scan will provide an accurate diagnosis.
Image credit: Drriad, 2010

During the physical exam, the doctor will listen to the lungs with a stethoscope. They may also tap on the chest to hear any signs of liquid.

The next step is an imaging test, which may be an X-ray or CT scan.

On an X-ray, plural effusions look white, and the lung tissue appears black as can be seen in the X-rays from a case report of a person with a pleural effusion.

The lung on the right side of image A at the link above shows little signs of liquid. The lung on the left side of the image shows a large white area, meaning that a pleural effusion is present. Image B illustrates quite clearly the amount of liquid in the chest.

CT scans provide more accurate images for doctors to help determine the underlying cause.

One of the most important steps in diagnosis is determining the type of effusion the person has. There are two types of effusions: transudate or exudate.

Transudate effusion

A transudate effusion is usually caused by fluid leaking back into the chest due to other disorders that cause a pressure imbalance in the blood vessels. The liquid in the effusion is typically made up of compounds found in the blood plasma.

Exudate effusion

Exudate effusions are more difficult to treat and can result in more serious issues. They are usually caused by inflammatory disorders, such as cancers, infections, and traumatic injuries. They may also be caused by blocked blood or lymph vessels in the area.

Doctors will often take a sample of the liquid in the pleural space by inserting a needle between the ribs into the pleural space and removing a small amount of fluid.

Liquid samples can help doctors look for signs of infections, protein levels, and cancer cells to determine whether the individual has a complicated or uncomplicated pleural effusion.

The fluid in a complicated pleural effusion is likely to show definite signs of inflammation or infection. Complicated pleural effusions require immediate treatment as they may cause serious problems.

An uncomplicated effusion creates a liquid that has no signs of infection or inflammation. Uncomplicated effusions may be milder and are much less likely to result in permanent lung damage.

Doctors may also order other tests to help find the cause of the effusion. These tests can include:

  • kidney function tests to determine if the kidneys are shutting down
  • liver function tests to look for signs of cirrhosis or failure
  • lung biopsy to investigate for signs of lung cancer
  • bronchoscopy to check for potential breathing problems and signs of tumors
  • heart ultrasound to check for evidence of heart failure

All of these tests help narrow down the cause of pleural effusion and make treatment as simple as possible.

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The fluid will need to be drained from the pleural space, so a doctor will use a needle or tube.

The treatment for pleural effusion depends on the disorder in the body that is causing it. In addition to treating the condition that is causing the effusion, in most cases, doctors will drain the fluid from the chest.

Chest draining

Chest draining is done by inserting a needle or tube into the pleural space and draining the fluid out of the body. The process does not require general anesthesia.

A local anesthetic is given to numb the pain of the cut, which most people tend to feel once the numbness wears off.

The process may need to be done more than once if the fluid continues to collect in the pleural space.

There is a small risk of serious complications from chest draining. These complications include infection, bleeding, or a collapsed lung. If the liquid is drained too fast, it is also possible for fluid to get into the lungs themselves. These are rare complications, however.

Other treatments

Other treatment routes may be necessary in some cases. Pleurodesis is the process of closing the gap between the pleura of the lung and chest cavity to prevent liquid from building up between them.

More severe cases may also require surgery to direct fluid from the chest cavity into the abdomen. Doctors may also remove a part of the pleural lining in very serious cases.

Pleural effusions can vary from non-serious to life-threatening. Outlook largely depends on the cause of the effusion. The time it takes to heal depends on the seriousness of the effusion.

Pleural effusions may require a person to be hospitalized and monitored. Following the guidance of a doctor, people can often find a treatment plan for the effusion.