Pleural Effusion – Pathophysiology
A pleural effusion is an abnormal amount of fluid around the lung. Pleural effusions can result from many medical conditions. Most pleural effusions are not serious by themselves, but some require treatment to avoid problems.
Causes of Pleural Effusions
The pleura is a thin membrane that lines the surface of the lungs and the inside of the chest wall outside the lungs. In pleural effusions, fluid accumulates in the space between the layers of pleura. Normally, only teaspoons of watery fluid are present in the pleural space, allowing the lungs to move smoothly within the chest cavity during breathing.
Numerous medical conditions can cause pleural effusions. Some of the more common causes are:
Congestive heart failure
Liver disease (cirrhosis)
End-stage renal disease
Lupus and other autoimmune conditions
Excessive fluid may accumulate because the body does not handle fluid properly (such as in congestive heart failure, or kidney and liver disease). The fluid in pleural effusions also may result from inflammation, such as in pneumonia, autoimmune disease, and many other conditions.
Symptoms of Pleural Effusions
Pleural effusions often cause no symptoms. Symptoms are more likely when a pleural effusion is moderate or large-sized, or if inflammation is present. Symptoms of pleural effusions may include:
Shortness of breath
Chest pain, especially on breathing in deeply (pleurisy, or pleuritic pain)
Because pleural effusions are usually caused by underlying medical conditions, symptoms of these conditions are also often present.
Diagnosis of Pleural Effusions
A doctor may suspect a pleural effusion based on a person’s symptoms and physical examination. Doctors may use auscultation (listening with a stethoscope), percussion (tapping on the chest), and other maneuvers when a pleural effusion is suspected.
Most often, pleural effusions are discovered on imaging tests. Common tests used to identify pleural effusions include:
Chest X-ray film: Plain X-ray films of the chest are often the first step in identifying a pleural effusion. Pleural effusions appear on chest X-rays as white space at the base of the lung. If a pleural effusion is likely, additional X-ray films may be taken while a person lies on her side. Called decubitus X-ray films, these can show if the fluid flows freely within the chest.
Diagnosis of Pleural Effusions continued…
Computed tomography (CT scan):A CT scanner takes multiple X-rays rapidly, and a computer constructs images of the inside of the chest. Compared to chest X-rays, CT scans produce more detailed information about pleural effusions and other lung abnormalities.
Ultrasound: A probe placed against the skin reflects high-energy sound waves off structures in the chest, creating images on a video screen. Ultrasound can help guide drainage and identify whether pleural effusions are free-flowing.
Once a pleural effusion is identified on imaging, a fluid sample is usually taken to determine the pleural effusion’s character and seriousness. In a procedure called thoracentesis, a doctor inserts a needle and a catheter between the ribs, into the pleural space. A small amount of fluid is withdrawn for testing; a large amount can be removed simultaneously to relieve symptoms.
Types of Pleural Effusions
There are two main categories of pleural effusions:
Uncomplicated pleural effusion: The pleural effusion contains fluid that is free of serious inflammation or infection. If large enough, an uncomplicated pleural effusion can cause symptoms. However, these pleural effusions rarely cause permanent lung problems.
Complicated pleural effusion: A complicated pleural effusion contains fluid that has significant inflammation or infection. If untreated, complicated pleural effusions may harden to form a constricting ring around the lung. This hardening process, called organization, can permanently impair breathing. To prevent organization, complicated pleural effusions require drainage, usually with a tube placed into the chest.
Doctors also use the terms transudative and exudative to describe pleural effusions:
Transudative: The pleural effusion fluid is similar in character to the fluid normally present in the pleural space. Transudative pleural effusions rarely require drainage, unless they are very large. Congestive heart failure is an example of a condition that can cause a transudative pleural effusion.
Exudative: The pleural effusion fluid has excess protein, blood, or evidence of inflammation or infection. An exudative pleural effusion may require drainage, depending on its size and the severity of inflammation. Causes of exudative pleural effusion include pneumonia and lung cancer.
The type of pleural effusion can only be identified by taking a sample of fluid from the pleural effusion.
Treatment of Pleural Effusions
Treatment for pleural effusions may often simply mean treating the medical condition causing the pleural effusion. Examples include giving antibiotics for pneumonia, or diuretics for congestive heart failure.
Large, infected, or inflamed pleural effusions often require drainage to improve symptoms and prevent complications. Various procedures may be used to treat pleural effusions, including:
Thoracentesis (described above) can remove large amounts of fluid, effectively treating many pleural effusions.
Tube thoracotomy (chest tube): A small incision is made in the chest wall, and a plastic tube is inserted into the pleural space. Chest tubes are attached to suction and are often kept in place for several days.
Pleurodesis: An irritating substance (such as talc or doxycycline) is injected through a chest tube, into the pleural space. The substance inflames the pleura and chest wall, which then bind tightly to each other as they heal. Pleurodesis can prevent pleural effusions from recurring, in many cases.
Pleural drain: For pleural effusions that repeatedly recur, a long-term catheter can be inserted through the skin into the pleural space. A person with a pleural catheter can drain the pleural effusion periodically at home.
Pleural decortication: Surgeons can operate inside the pleural space, removing potentially dangerous inflammation and unhealthy tissue. Decortication may be performed using small incisions (thoracoscopy) or a large one (thoracotomy).
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