Diseases & Conditions A - Z
powered by Talix

Fluid in the Chest (Pleural Effusion)

What is pleural effusion?

Pleural effusion, also called "water on the lung," is an excessive buildup of fluid in the space between your lungs and chest cavity. Thin membranes, called pleura, cover the outside of the lungs and the inside of the chest cavity. There’s always a small amount of liquid within this lining to help lubricate the lungs as they expand within the chest during breathing.

Certain medical conditions can cause a pleural effusion.

Pleural effusions are common, with approximately 1.5 million cases diagnosed in the United States every year, according to the American Thoracic Society. It is a serious condition associated with an increased risk of death. One study has shown that 15 percent of hospitalized people diagnosed with pleural effusions die within 30 days.

How does pleural effusion develop?

The pleura creates too much fluid when it’s irritated or infected. This fluid accumulates in the chest cavity outside the lung, causing what’s known as a pleural effusion.

Certain types of cancer can cause pleural effusions. Lung and breast cancer are the most common causes.

Other causes of pleural effusions include:

Types of pleural effusions

There are several types of pleural effusions, with different causes and treatment options. The first classification of pleural effusions is transudative pleural effusions and exudative pleural effusions.

Transudative pleural effusions

This type is caused by fluid leaking into the pleural space as a result of either a low blood protein count or increased pressure in the blood vessels. Its most common cause is congestive heart failure.

Exudative effusions

This type is caused by:

  • blocked lymph or blood vessels
  • inflammation
  • tumors
  • lung injury

Common conditions that could result in this type of pleural infusion include pulmonary embolisms, pneumonia, and fungal infections.

Complicated and uncomplicated pleural effusions

There are also complicated and uncomplicated pleural effusions. Uncomplicated pleural effusions contain fluid without signs of infection or inflammation. They’re much less likely to cause permanent lung problems.

Complicated pleural effusions, however, contain fluid with significant infection or inflammation. They require prompt treatment that frequently includes chest drainage.

Symptoms and signs of pleural effusion

Some people show no symptoms of pleural effusion. These people usually find out they have the condition through chest X-rays or physical examinations ordered for another reason.

Common symptoms of pleural effusion include:

See your doctor immediately if you have symptoms of pleural effusion.

Diagnosing pleural effusion

Your doctor will perform a physical examination and listen to your lungs with a stethoscope. He or she may also order a chest X-ray to help diagnose pleural effusion. Other possible tests include:

In a pleural fluid analysis, your doctor will remove fluid from the pleural membrane area by inserting a needle into the chest cavity and suctioning the fluid into a syringe. The procedure is called a thoracentesis. The fluid will then be tested to determine the cause.

Your doctor may schedule a thoracoscopy if they discover you have a pleural effusion, but they’re unable to diagnose which type. A thoracoscopy is a surgical procedure that lets the doctor see inside the chest cavity using a fiber optic camera.

Your doctor will make a few small incisions in the chest area while you’re under general anesthesia. Then they’ll insert the camera through one incision and the surgical tool through the other incision to extract a small amount of fluid or tissue for analysis.

Treating pleural effusion

The underlying cause of the condition and the severity of the effusion will determine treatment.

Draining fluid

Generally, treatment involves draining the fluid from the chest cavity, either with a needle or a small tube inserted into the chest. You’ll receive a local anesthetic before this procedure, which will make the treatment more comfortable. You may feel some pain or discomfort at the incision site after the anesthetic wears off. Most doctors will prescribe medication to help relieve pain. You may need this treatment more than once if fluid re-collects.

Other treatments may be necessary to manage fluid buildup if cancer is the cause of the pleural effusion.


Pleurodesis is a treatment that creates mild inflammation between the lung and chest cavity pleura. After drawing the excess fluid out of the chest cavity, a doctor injects a drug into the area. The drug is often talc. This medication causes the two layers of the pleura to stick together and prevents the buildup of fluid between the two layers by getting rid of the space between them.


In more serious cases, a doctor surgically inserts a shunt, or small tube, into the chest cavity. This helps redirect the fluid from the chest to the abdomen, where it can be easily removed. Pleurectomy, in which part of the pleural lining is surgically removed, is also an option in very severe cases.

Risks of pleural effusion treatment

Treatment for minor cases of pleural effusion is minimally invasive. Most people recover within a few days. Minor complications from treatment include slight pain and discomfort, which often go away with time. Some cases of pleural effusion can have more serious complications, depending on the severity of the condition and treatment used.

Serious complications include:

  • pulmonary edema or fluid in the lungs, which can result from draining fluid too quickly during thoracentesis
  • partial collapsed lung
  • infection or bleeding

These complications, while serious, are very rare. Your doctor will help determine the most effective treatment option and will discuss the benefits and risks of each procedure.

Pleural effusions and cancer

Pleural effusions can be the result of cancer cells spreading to the pleura. They can also be the result of cancer cells blocking the flow of normal fluid within the pleura. Fluid may also build up as a result of certain cancer treatments, such as radiation therapy or chemotherapy.

Certain cancers are more likely to cause pleural effusions than others, including:

Signs and symptoms include:

  • shortness of breath
  • cough
  • chest pain

Pleurodesis is often used as a treatment for the malignant pleural effusions caused by cancer. Antibiotics may also be used if you have or are susceptible to an infection. Steroids or other anti-inflammatory medications may be used to reduce pain and inflammation.

In addition to treating the pleural effusion, your doctor will treat the cancer that caused it. Pleural effusions are typically the result of metastatic cancer.

People who are undergoing treatment for cancer may also have compromised immune systems, making them more prone to infections or other complications.

What is the outlook for a pleural effusion?

Pleural effusions can be serious and life-threatening. Many require hospitalized treatment and some require surgery. The time it takes to recover from pleural effusions depends on the cause, size, and severity of the effusion, as well as your overall health.

You will begin your recovery in the hospital, where you’ll receive the necessary medication and care to help you begin to recover. Many people report feeling tired and weak in the first week after they’ve been discharged from the hospital. On average, you will see your incision sites from surgery heal within two to four weeks.

Content licensed from:

Written by: April Kahn and Ana Gotter
Medically reviewed on: Aug 25, 2016: Judith Marcin, MD

This feature is for informational purposes only and should not be used to replace the care and information received from your health care provider. Please consult a health care professional with any health concerns you may have.
Symptom Search
Enter your symptoms in our Symptom Checker to find out possible causes of your symptoms. Go.
Drug Interaction Checker
Enter any list of prescription drugs and see how they interact with each other and with other substances. Go.
Pill Identifier
Enter its color and shape information, and this tool helps you identify it. Go.
Drugs A-Z
Find information on drug interactions, side effects, and more. Go.