Pleural Effusion

The medical definition of pleural effusion is that of an “abnormal accumulation of fluid in the pleural space” (1). It is essentially a build-up of fluids in the space around the lungs which restricts the lungs from expanding.

Pleural effusion is not, by itself a disease. It can however be indicative of any number of pathological conditions of the respiratory system – including different types of cancer.

The Pleural Lining

All internal organs are covered by a slick, lubricating membrane. This membrane has different specific appellations, depending on the organ or surface it covers; however, in generic terms, these membranes are all considered part of the mesothelium. The mesothelium covering the lungs is known as the pleura, or pleural lining.

The pleura is made up of an inner layer, which covers the surfaces of the lungs themselves, and an outer layer which lines the rib cage and diaphragm.

Through the lymphatic system, the pleura produces a lubricant fluid that allows the lungs to expand and move against other surfaces without irritation or discomfort (2). This fluid serves the same function in the body as oil in a machine; without proper lubrication, for example, an automobile would wear out very quickly.

Normally, there is no more than 15 ml. of fluid in the space between the inner and outer pleural layers. This fluid is circulated through the body’s lymphatic system, which is capable of draining as much as 300 ml. of fluid at any given time. Pleural effusion results when for some reason, more of this fluid is produced that the lymphatic system can absorb, or the lymphatic system is compromised and unable to function properly (3).

As the fluid builds up, it exerts pressure on the lungs, preventing them from expanding and reducing air capacity.

Types and Causes of Pleural Effusion

Pleural effusion can be caused by bacterial infection, in which case it is known as pyrothorax or empyema. The fluid which builds up in this case is pus, a mixture of proteins and dead white blood cells which is a by-product of inflammation resulting from an immune system reaction to an foreign (exogenous) organic pathogen, i.e., bacteria.

Hemothorax is a condition in which blood builds up in the pleura cavity. This is invariably caused by an injury or trauma to the chest.

Chylothorax is a type of pleural effusion that can also be the result of an injury or trauma (generally in the course of surgery), but is more often a sign of lymphoma, or cancer of the lymph nodes – in some cases known as Hodgkin’s Disease.

Pneumothorax is the complete collapse of the lung, which may be caused by pleural effusion (though it may be due to other factors as well).

Hydrothorax is the generic term for any build-up of bodily, or serous fluids in the pleural cavity (4).

Pleural effusions are common in cases of pneumonia, and can be a sign of impending heart failure, as poor circulation due to a weak heart can result in fluid build-up in the pleural cavity. In this case, the pleural effusion is considered transudate – the direct cause is something other than a respiratory problem. This also includes breast and ovarian cancer.

If the effusion is due to a condition in the respiratory system itself, it is considered exudate. Carcinoma of the lung, or lymphatic system can lead to pleural effusion. It is especially common in cancer of the pleura itself, or mesothelioma (5).

Symptoms and Diagnosis of Pleural Effusion

One of the problems in diagnosing respiratory diseases is that many of them have similar symptoms – shortness of breath, chest pains, and coughing. Generally, an accurate diagnosis of pleural effusion requires additional – and sometimes invasive – testing.

Treatment

Regardless of the cause, the fluid build-up of a pleural effusion must be drained in order to relieve the pressure on the lungs.

In this procedure, the patient sits on a chair or the edge of a bed and leaned forward in order to expose the upper back. Typically, the physician will mark the side of the chest where the drain is to be inserted, cleanse the area with antiseptic and inject a local anesthetic.

Once this has been done, the physician will make a small incision and insert a needle known as a cannula. This is essentially a hollow steel tube cut at an angle and attached to a flexible plastic tube (also used for I.V. and intravenous feeding). This tube is attached to a drainage bag or bottle into which the fluid is collected.

The length of time required for this procedure varies, depending on how much fluid must be drained; this may be anywhere from a few minutes to two days. As the rate of flow lessens and the physician determines most of the fluid has been removed, s/he will order an x-ray to ensure the lung is again functioning properly.

Once all the fluid has been drained, the incision is sutured if necessary and a clean dressing is applied. Pain medication may be administered after the local anesthetic wears off.

Some patients in which such pleural effusions are recurring (as with mesothelioma) may be able to have this procedure done on a out-patient basis. Instead of a cannula, a catheter is installed with a suction bottle attached, which is then clamped off and covered with a sterile dressing.

It is important that such fluids not be drained too rapidly; if pressure in the chest is released all at once, it could result in a dangerous drop in blood pressure. If performed in a hospital, a nurse will be on-hand to monitor blood pressure. Patients should inform the attending physician of any dizziness or light-headedness.

One procedure sometimes performed on mesothelioma and lung cancer patients is pleurodesis. Once the fluid has been removed, a surgeon may decide to seal the two layers of the pleural lining together in order to prevent further fluid build-up.

This procedure involves injecting some type of drug, such as bleomycin or tetracycline into the pleural cavity. Once this has been done, reverse pressure through a catheter or cannula is used to draw the layers together. With cancer patients, this is often done in conjunction with chemotherapy and/or radiation treatments (6).

'Pleural Effusion' Resources:

Notes

  1. Abrahamian , Frederick M. “Pleural Effusion”
  2. CancerBackup. “Pleural Effusions”
  3. Wikipedia. “Pleural Effusion”
  4. Ibid.
  5. CancerBackup, op. cit.
  6. Ibid.

 Sources

  1. Abrahamian , Frederick M. “Pleural Effusion” (Online Article). Updated 27 June, 2005.
    Accessed: 22 September 2007.
  2. CancerBackup. “Pleural Effusions” (Online Article).Updated 8 June 2007.
    Accessed: 22 September 2007.
  3. Wikipedia. “Pleural Effusion” (Online Article).Updated 10 September 2007.
    Accessed: 22 September 2007.