©2018 WebMD, Inc. All rights reserved. eMedicineHealth does not provide medical advice, diagnosis or treatment. See Additional Information.

Pleural Effusion

  • Medical Author:
    Benjamin Wedro, MD, FACEP, FAAEM

    Dr. Ben Wedro practices emergency medicine at Gundersen Clinic, a regional trauma center in La Crosse, Wisconsin. His background includes undergraduate and medical studies at the University of Alberta, a Family Practice internship at Queen's University in Kingston, Ontario and residency training in Emergency Medicine at the University of Oklahoma Health Sciences Center.

  • Medical Editor: Charles Patrick Davis, MD, PhD
    Charles Patrick Davis, MD, PhD

    Charles Patrick Davis, MD, PhD

    Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

Pleural Effusion Related Articles

Pleural Effusion Facts

  • Pleural effusions describe fluid between the two layer 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.

Pleural Effusion Overview

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 bellows. 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. A small amount of fluid acts 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.

Picture of pleural effusion
Picture of pleural effusion

Pleural Effusion Causes

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 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; and 2) exudate pleural effusions. Sometimes the pleural effusion can have characteristics of both a transudate and an exudate.

1. 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:

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

Examples of exudate causes include:

Most pleural effusions are caused by congestive heart failure, pneumonia, pulmonary embolism (blood clot in the lung), and malignancy.

Pleural Effusion 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.


COPD (chronic obstructive pulmonary disease) is the same as adult-onset asthma. See Answer

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

When to Seek Medical Care

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, calling 911 and activating emergency care services may be appropriate.

Pleural Effusion Diagnosis

The diagnosis of a pleural effusion begins with the health care practitioner taking the patient's history. Physical examination 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 tapping 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 a 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 afterwards to make certain that the procedure did not cause a pneumothorax (collapsed lung). Analysis of the pleural fluid include:
    • 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 blood stream. 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 upon associated symptoms and the direction taken by the doctor in searching for the underlying diagnosis that caused the pleural effusion.

Pleural Effusion Treatment

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 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 empyemas (pus collections).

Pleural Effusion Complications

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 permanent decrease in lung function. Fluid that remains for a prolonged period of time is also at risk for 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 recurrence. If sclerosing agents fail, surgery may be required.


COPD Foods to Boost Your Health - COPD Diet Tips See Slideshow

Pleural Effusion Prevention

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

Pleural Effusion 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.

Health Solutions From Our Sponsors

Reviewed on 10/18/2018
Medscape. Pleural Effusion.

Medscape. Pleural Effusion: Differential Diagnoses & Workup.

Patient Comments & Reviews

  • Pleural Effusion - Signs and Symptoms

    Please discuss the signs and symptoms associated with your case of pleural effusion.

    Post View 4 Comments
  • Pleural Effusion - Treatment

    How was your case of pleural effusion treated?

    Post View 8 Comments