PLEURAL EFFUSION DEFINITION
A pleural effusion is a buildup of fluid in the pleural space, an area between the layers of tissue that line the lungs and the chest cavity. It may also be referred to as effusion or pulmonary effusion. The type of fluid that forms a pleural effusion may be categorized as either transudate or exudate. Transudate is usually composed of ultrafiltrates of plasma due to an imbalance in vascular hydrostatic and oncotic forces in the chest (heart failure, cirrhosis), while exudate is typically produced by inflammatory conditions (lung infection, malignancy). Exudative pleural effusions are usually more serious and difficult to treat.
PLEURAL EFFUSION CAUSES
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
- Nephrotic syndrome
- Pulmonary embolism
- 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 liverdisease). The fluid in pleural effusions also may result from inflammation, such as in pneumonia, autoimmune disease, and many other conditions.
PLEURAL EFFUSION PATHOPHYSIOLOGY
A pleural effusion is an abnormal collection of fluid in the pleural space resulting from excess fluid production or decreased absorption or both. It is the most common manifestation of pleural disease, with etiologies ranging from cardiopulmonary disorders to symptomatic inflammatory or malignant diseases requiring urgent evaluation and treatment. Approximately 1.5 million pleural effusions are diagnosed in the United States each year.
PLEURAL EFFUSION SYMPTOMS
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.
PLEURAL EFFUSION DIAGNOSIS
The patient’s history and physical exam may indicate a presumptive diagnose of pleural effusion. For example, a patient with a history of congestive heart failure or cirrhosis with symptoms of cough, difficulty breathing, and pleuritic chest pain may have a pleural effusion. Findings from the physical exam, such as dullness to percussion of the lung area (when tapping the area of the lung with a finger, the percussion or sound is dull – if no fluid exists in the area the sound will be lighter – please see this for an informational video by the Stanford School of Medicine on percussion of the chest), decreased vibration (decreased tactile fremitus), and asymmetrical chest expansion (the lungs do not inflate or deflate equally – please see this for an informational YouTube video about asymmetrical chest expansion) may also be evidence of a pleural effusion. Other physical exam findings detected with a stethoscope may include reduced or inaudible breath sounds on the affected side, egophony (patient voices the letter “e,” but when listening [auscultation] it sounds like “a”), and a friction rub (if there is fluid in the pleural area, the heart will rub against the inflamed or fluid filled space). To hear what a friction rub sounds like please see this informational YouTube video.
Chest X-ray can detect pleural effusions, as they usually appear as whitish areas at the lung base, and they may occur on only one side (unilateral) or on both sides (bilateral). If a person lies on their side for a few minutes, most pleural effusions will move and layer out along that side of the chest cavity which is positioned downward (because of the effects of gravity). This movement of the pleural effusion can be seen on an X-ray taken with the person lying on their side (a lateral decubitus X-ray).
Other imaging tests, such as CT scan, may be ordered to further identify the possible cause and the extent of the pleural effusion.
Diagnosing the cause(s) of a pleural effusion often begins with determining whether the fluid is transudate or exudate. This is important because the results of this fluid analysis may provide a diagnosis and determine the course of treatment. Thoracentesis (a procedure to remove the fluid from the pleural space) followed by laboratory analysis of the fluid can differentiate between transudate and exudate. The results from the fluid obtained from the thoracentesis are compared to certain blood tests (for example, LDH, glucose, protein, pH, cholesterol and others). Additional testing of the pleural fluid may also include a cell count, cytology, and cultures. Criteria are then used to differentiate exudate from transudate. Exudate has the following characteristics:
- Pleural fluid LDH > 0.45 of the upper limits of normal blood values
- Pleural fluid protein level > 2.9g/dL
- Pleural fluid cholesterol level > 45mg/Dl
PLEURAL EFFUSION TREATMENT
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).