What is pleural effusion?

Pleural effusion is when excess fluid builds up in the pleural space of the lungs.

The lungs are surrounded by a thin membrane, the inner layer of pleura. A second, outer membrane lines the inside of the chest cavity attaching to the ribcage. The narrow pleural space between the two membranes contains about four teaspoons (10-20mls) of fluid. [1] This fluid allows the two layers to glide smoothly across one another as the lungs expand and contract during breathing.

The fluid enters the pleural space from blood capillaries, and drains through lymph ducts. If excess fluid builds up in the pleural space, this is known as pleural effusion.

Pleural effusion can be the result of many medical conditions, and an analysis of the effusion can be useful for diagnosing these conditions.

Pleural effusion is a build-up of fluid in the pleural space. 

Lymph

A fluid containing lymphocytes (small white blood cells) that circulates through the body and moves through the lymphatic system into the bloodstream.

Pleura

The pleura is the two thin linings that coat the lungs and internal chest cavity.

Pleural space

The space in between the two thin linings that coat the lungs and internal chest cavity.

1. Murtagh, J. (2008) John Murtagh’s Patient Education (Australian edition.). North Ryde, N.S.W.: McGraw-Hill Book Company Australia.

Causes

Pleural effusion can be the result of many disorders, including: [1] [2] [3]

Inflammation

A body’s protective immune response to injury or infection. The accumulation of fluid, cells and proteins at the site of an infection or physical injury, resulting in swelling, heat, redness, pain and loss of function.

Liver

A large, internal organ of the body, located on the upper right-hand side of the abdomen. The liver has hundreds of distinct functions, including producing bile, regulating the body's metabolism and detoxifying the blood.

Liver failure

A serious condition in which the liver is unable to function adequately.

Lymphoma

A tumor of lymph tissue, which is rich in lymphocytes, small white blood cells that have specific immune responses.

Pancreas

An organ located behind the stomach that secretes insulin and glucagon into the bloodstream and digestive enzymes into the intestines.

1. Murtagh, J. (2008) John Murtagh’s Patient Education (Australian edition.). North Ryde, N.S.W.: McGraw-Hill Book Company Australia.

2. Porcel, J.M. and Light, R.W. (2013) Pleural effusions. Disease-a-Month 59:29–57.

3. Kastelik, J.A. (2013) Management of malignant pleural effusion. Lung 191:165–175.

Signs and symptoms

General signs and symptoms of pleural effusion include:

  • Coughing;
  • Chest pain, and;
  • Shortness of breath and rapid breathing.

Additional signs and symptoms can appear, depending on the type and cause of the effusion.

1. Murtagh, J. (2008) John Murtagh’s Patient Education (Australian edition.). North Ryde, N.S.W.: McGraw-Hill Book Company Australia.

2. Porcel, J.M. and Light, R.W. (2013) Pleural effusions. Disease-a-Month 59:29–57.

3. Kastelik, J.A. (2013) Management of malignant pleural effusion. Lung 191:165–175.

Methods for diagnosis

Your doctor will diagnose pleural effusion by:

Your doctor will determine the cause of pleural effusion by aspirating the pleural fluid - taking a sample of fluid from your pleura using a needle and syringe. The fluid sample is then analyzed for the presence of blood, bacteria, immune cells, a tumor, and levels of glucose and certain proteins.

Bacteria

Microscopic, single-celled organisms with DNA but no definite nucleus. Bacteria are the cause of many human diseases.

Computerized tomography

A scan that uses X-rays to create a 3D image of the body. This can detect abnormalities more effectively than a simple X-ray can.

Glucose

A simple sugar found in many foods (such as fruit) that functions as a major energy source for the body.

Pleura

The pleura is the two thin linings that coat the lungs and internal chest cavity.

Tumor

A growth caused by an abnormal and uncontrolled reproduction of cells.

Bronchoscopy

A procedure involving internal visualization of the larynx, trachea and bronchi by using a bronchoscope (a flexible scope that goes down the throat).

Thoracoscopy

A surgical procedure that uses a thoracoscope, a thin scope that is inserted into the chest cavity through small incisions, to inspect and treat lung problems.

Immune cells

Cells of the immune system that protect the body from infections.

2. Porcel, J.M. and Light, R.W. (2013) Pleural effusions. Disease-a-Month 59:29–57.

Types of treatment

The treatment of pleural effusion depends on the cause, and on whether the person has symptoms as a result of the pleural fluid.

For pleural effusions due to underlying medical conditions, such as heart failure and liver disease, optimizing the management of these conditions is necessary. This can be combined with drainage of the pleural fluid, using a procedure called thoracentesis (see below). Without treating the underlying condition, the pleural effusion will re-accumulate. Infections caused by bacteria are treated with antibiotics. Pleural effusions due to cancer need specialist treatment, as therapies depend on the type of cancer. 

Thoracentesis

To treat pleural effusion, a doctor can remove the excess fluid using a needle and syringe, or by inserting a tube into your pleural space. This is known as thoracentesis, or 'tapping', and can be done periodically if fluid keeps building up. In some cases, draining tubes may be left in the chest cavity.

Pleurodesis

In particular cases of pleural effusion, your doctor may suggest pleurodesis, a procedure in which the two layers of the pleura are fused together. This is performed for recurrent pleural effusions that do not respond to other therapies.

Bacteria

Microscopic, single-celled organisms with DNA but no definite nucleus. Bacteria are the cause of many human diseases.

Liver

A large, internal organ of the body, located on the upper right-hand side of the abdomen. The liver has hundreds of distinct functions, including producing bile, regulating the body's metabolism and detoxifying the blood.

Pleura

The pleura is the two thin linings that coat the lungs and internal chest cavity.

Pleural space

The space in between the two thin linings that coat the lungs and internal chest cavity.

2. Porcel, J.M. and Light, R.W. (2013) Pleural effusions. Disease-a-Month 59:29–57.

Potential complications

In addition to being a sign of another condition, if left untreated, pleural effusions can lead to complications such as:

  • The pressure exerted by the fluid can lead to a collapsed lung, and
  • Empyema - the fluid in the pleural space can become infected, leading to an abscess.

Collapsed lung

When air enters the space between the lung and the wall of the chest (the pleural space), the lung collapses, making breathing difficult. This can occur due to injury or as a result of lung disease.

Pleural space

The space in between the two thin linings that coat the lungs and internal chest cavity.

2. Porcel, J.M. and Light, R.W. (2013) Pleural effusions. Disease-a-Month 59:29–57.

Prognosis

In some people, pleural effusions (especially those caused by viral infection) will improve and go away by themselves without treatment within 1-8 weeks. [2]

For others, pleural effusions will recur if the underlying cause is not treated successfully. In these cases, the fluid will be periodically drained whenever it accumulates.

Infection

Entry into the body of microorganisms that can reproduce and cause disease.

Viral

Pertaining to an illness caused by a virus.

2. Porcel, J.M. and Light, R.W. (2013) Pleural effusions. Disease-a-Month 59:29–57.