Pleural Effusion

Reviewed on 11/14/2022

What to Know About Pleural Effusion (Fluid Around the Lungs)

Picture of pleural effusion
Lung scarring and a permanent decrease in lung function are associated with chronic pleural effusion.
  • Pleural effusions describe fluid between the two layers of tissue (pleura) that cover the lung and the lining of the chest wall.
  • A pleural effusion is due to the manifestations of another illness.
  • In general, pleural effusions can be divided into transudates (caused by fluid leaking from blood vessels) and exudates (where fluid leaks from inflammation of the pleura and lung).
  • The most common causes of pleural effusion are congestive heart failure, pneumonia, malignancies, and pulmonary embolism.
  • Signs and symptoms of pleural effusion include:
  • Associated symptoms of pleural effusion due to an underlying disease include:
  • Thoracentesis is used to draw off the pleural fluid for analysis. A thin needle is inserted between the ribs into the fluid collection.
  • Treatment of the pleural effusion depends upon the underlying illness.

What Is Pleural Effusion?

A pleural effusion is a collection of fluid in the space between the two linings (pleura) of the lung.

When we breathe, it is like a bellow. We inhale air into our lungs and the ribs move out and the diaphragm moves down. For the lung to expand, its lining has to slide along with the chest wall movement. For this to happen, both the lungs and the ribs are covered with a slippery lining called the pleura. Small amounts of fluid act as a lubricant for these two surfaces to slide easily against each other.

Too much fluid impairs the ability of the lung to expand and move.

What Are Symptoms and Signs of Pleural Effusion?

Shortness of breath is the most common symptom of a pleural effusion. As the effusion grows larger with more fluid, the harder it is for the lung to expand and the more difficult it is for the patient to breathe.

Chest pain occurs because the pleural lining of the lung is irritated. The pain is usually described as pleuritic, defined as a sharp pain, and it worsens with a deep breath. While the pain may be localized to the chest if the effusion causes inflammation of the diaphragm (the muscle that divides the chest from the abdominal cavity) the pain may be referred to the shoulder or the upper abdomen. As the pleural effusion increases in size, the pain may increase.

Other associated symptoms are due to the underlying disease. For example, individuals with:

  • Congestive heart failure may have signs and symptoms of swelling of the feet and shortness of breath when lying flat (orthopnea) or wakening in the middle of the night (paroxysmal nocturnal dyspnea).
  • Tuberculosis may have symptoms of night sweats, coughing up blood (hemoptysis), and weight loss.
  • Hemoptysis may have associated infection and lung cancer.
  • Pneumonia may have signs and symptoms of fever, shaking chills, coughing up colored sputum, and pleuritic pain.

What Causes a Pleural Effusion? What Are the Types?

A pleural effusion is not normal. It is not a disease but rather a complication of an underlying illness. Extra fluid (effusion) can occur for a variety of reasons.

Common classification systems (types) divide pleural effusions based on the chemistry composition of the fluid and what causes the effusion to be formed. Two classifications are:

  1. transudate pleural effusions
  2. exudate pleural effusions

Sometimes the pleural effusion can have characteristics of both a transudate and an exudate.

Transudate pleural effusions

Transudate pleural effusions are formed when fluid leaks from blood vessels into the pleural space. Chemically, transudate pleural effusions contain less protein and LDH (lactate dehydrogenase) than exudate pleural effusions. If both the pleural fluid–to–serum total protein ratio is less than or equal to 0.50 and the pleural fluid–to–serum LDH ratios are less than or equal to 0.67, the fluid is usually considered to be a transudate while exudates ratios are above 0.50 and above 0.67.

Examples of transudate pleural effusions include:

Exudate pleural effusions

Exudate pleural effusions are caused by inflammation of the pleura, and are often due to disease of the lung.

Examples of exudate causes include:

Most pleural effusions are caused by:

Can a Pleural Effusion Cause Cancer (Malignancy)?

A malignant (cancerous) pleural effusion (MPE) is the buildup of fluid and cancer cells that collect between the chest wall and the lung. This can cause chest discomfort and shortness of breath. Cancer of the pleura is common. Pleural effusion is a complication in several different cancers, for example:

Who Gets Pleural Effusion? What Are the Risk Factors?

Since a pleural effusion is a manifestation of another illness, the risk factors are those of the underlying disease. In general, pleural effusions are seen in adults and less commonly in children.

When Should You Call a Doctor for Pleural Effusion?

Chest pain and shortness of breath are two symptoms that should almost always prompt a person to seek medical care. Depending upon the circumstances and the severity of symptoms, call 911 or activate other emergency care services.

What Procedures and Tests Diagnose Pleural Effusion?

The diagnosis of a pleural effusion begins with the healthcare practitioner taking the patient's history. Physical examination is concentrated on the chest and may include listening (auscultating) to the heart and lungs and tapping on the chest (percussing). The presence of a pleural effusion may decrease air entry and cause dullness to tap on one side of the chest when compared to the other side. If pleurisy (inflammation of the pleura) is present, a friction rub or squeak may be heard.

  • Chest X-ray may help confirm the presence of fluid. Aside from the routine views of the chest, if pleuritic fluid is present, an additional X-ray view may be obtained with the patient lying on the side of the effusion. Called lateral decubitus, the X-ray will show whether the fluid layers out along the chest cavity.
  • Chest ultrasound may be used at the bedside as a quick way of confirming the fluid and its location. It can help decide whether the fluid is free-flowing within the pleural space or whether it is contained in a specific area (loculated).
  • CT scans may be used to image the chest and reveal not only the lung but other potential causes of the effusion.
  • Thoracentesis is a procedure used to sample the fluid from the pleural effusion. Using a long thin needle, fluid can be removed and sent for testing to confirm the diagnosis. Often, a chest X-ray is taken before the thoracentesis to confirm the presence of the effusion and afterward to make certain that the procedure did not cause a pneumothorax (collapsed lung). Analysis of the pleural fluid includes:
    • Chemical analysis may differentiate a transudate from an exudate by measuring the ratio of protein concentration in the pleural effusion and comparing it to the protein concentration in the bloodstream. Exudates have higher protein concentrations than transudates.
    • LDH (lactate dehydrogenase) is another chemical that can help make the distinction between the two types of effusion.
    • Complete blood cell count (CBC) analysis looking for infection, cell analysis looking for tumor cells, and cultures looking for infection.
  • Blood tests and other imaging studies may be considered based on associated symptoms and the direction taken by the doctor in searching for the underlying diagnosis that caused the pleural effusion.

What Is the Treatment and Management for Pleural Effusion?

  • Since a pleural effusion may compromise breathing, the ABCs (Airway, Breathing, and Circulation) of resuscitation are often the first consideration to make certain that there is enough oxygen available for the body to function.
  • The treatment of a pleural effusion usually requires that the underlying illness or disease is treated and controlled to prevent the accumulation of the pleural fluid.
  • While thoracentesis is used as a diagnostic procedure, it can also be therapeutic in removing fluid and allowing the lung to expand and function. Tube thoracostomy, also known as a chest tube, may be placed to drain and treat pus collections (empyemas).

What Are the Complications of Pleural Effusion?

  • Pleural effusions compromise lung function by preventing its full expansion for breathing. If the effusion is long-standing, there can be associated lung scarring and a permanent decrease in lung function. Fluid in the lungs that remains for a prolonged period is also at risk of becoming infected and forming an abscess called an empyema.
  • Diagnostic and therapeutic procedures including thoracentesis involve placing needles through the chest wall into the pleural space. Pneumothorax is a potential complication.
  • Some pleural effusions reoccur multiple times; sclerosing agents that induce scarring such as talc or tetracycline may be used to prevent a recurrence. If sclerosing agents fail, surgery may be required.

Is Pleural Effusion Serious? What Is the Prognosis?

Since a pleural effusion is a symptom of another disease, the prognosis depends upon the underlying illness. Pleural effusions are never normal. While they may be associated with treatable illnesses, their presence suggests that the underlying disease has advanced enough to cause significant inflammation of the lining of the lung.

Can You Prevent Pleural Effusion?

Pleural effusions are caused by a variety of conditions and illnesses. Preventing the underlying cause will decrease the potential of developing an effusion.

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Reviewed on 11/14/2022
Boka, K, MD. et al. Pleural Effusion Treatment & Management. Medscape. Updated: Dec 28, 2018.

Boka, K, MD. et al. Pleural Effusion: Differential Diagnoses. Medscape. Updated: Dec 28, 2018.