Pleural effusion

Definition

Pleural effusion occurs when too much fluid collects in the pleural space (the space between the two layers of the pleura). It is commonly known as "water on the lungs." It is characterized by shortness of breath, chest pain, gastric discomfort (dyspepsia), and cough.

Description

There are two thin membranes in the chest, one (the visceral pleura) lining the lungs, and the other (the parietal pleura) covering the inside of the chest wall. Normally, small blood vessels in the pleural linings produce a small amount of fluid that lubricates the opposed pleural membranes so that they can glide smoothly against one another during breathing movements. Any extra fluid is taken up by blood and lymph vessels, maintaining a balance. When either too much fluid forms or something prevents its removal, the result is an excess of pleural fluid—an effusion. The most common causes are disease of the heart or lungs, and inflammation or infection of the pleura.

Pleural effusion itself is not a disease as much as a result of many different diseases. For this reason, there is no "typical" patient in terms of age, sex, or other characteristics. Instead, anyone who develops one of the many conditions that can produce an effusion may be affected.

There are two types of pleural effusion: the transudate and the exudate. This is a very important point because the two types of fluid are very different, and which type is present points to what sort of disease is likely to have produced the effusion. It also can suggest the best approach to treatment.

A transudate is a clear fluid, similar to blood serum, that forms not because the pleural surfaces themselves are diseased, but because the forces that normally produce and remove pleural fluid at the same rate are out of balance. When the heart fails, pressure in the small blood vessels that remove pleural fluid is increased and fluid "backs up" in the pleural space, forming an effusion. Or, if too little protein is present in the blood, the vessels are less able to hold the fluid part of blood within them and it leaks out into the pleural space. This can result from disease of the liver or kidneys, or from malnutrition.

An exudate—which often is a cloudy fluid, containing cells and much protein—results from disease of the pleura itself. The causes are many and varied. Among the most common are infections such as bacterial pneumonia and tuberculosis; blood clots in the lungs; and connective tissue diseases, such as rheumatoid arthritis. Cancer and disease in organs such as the pancreas also may give rise to an exudative pleural effusion.

Some of the pleural disorders that produce an exudate also cause bleeding into the pleural space. If the effusion contains half or more of the number of red blood cells present in the blood itself, it is called hemothorax. When a pleural effusion has a milky appearance and contains a large amount of fat, it is called chylothorax. Lymph fluid that drains from tissues throughout the body into small lymph vessels finally collects in a large duct (the thoracic duct) running through the chest to empty into a major vein. When this fluid, or chyle, leaks out of the duct into the pleural space, chylothorax is the result. Cancer in the chest is a common cause.

— David A. Cramer, MD

(medicine) Abnormal accumulation of fluid in the area between the membranes lining the lungs and the chest cavity (the pleural space).

Key Terms: Parietal pleurae, Pleural space.

Description

Pleural effusion is the accumulation of fluid in the pleural space. The pleural space is the region between the outer surface of each lung (visceral pleurae) and the membrane that surrounds each lung (parietal pleurae). Under normal conditions, the pleurae are kept wet with pleural fluid to allow movement of the lungs within the chest. The pleural fluid comes from cells that make up the pleurae. Pleural fluid is continuously being produced and removed, a process that is precisely controlled by many factors. Cancer can interfere with this delicate balance within the pleural space causing fluid to accumulate.

Cancer is responsible for 40% of all pleural effusions, which are then called malignant pleural effusions. Pleural effusion is the first symptom of cancer for up to 50% of the patients. Thirty-five percent of the cases of malignant pleural effusion are caused by lung cancer, 23% by breast cancer, and 10% by lymphoma.

Chest x rays and computed tomography scans may be performed to diagnose pleural effusion. Thoracentesis, the removal of pleural fluid through a long needle, is usually performed for diagnostic purposes. Fluid removed by thoracentesis will be sent to the lab to be thoroughly evaluated. Thoracoscopy, in which a wand-like lighted camera (endoscope) is inserted through the chest, may be conducted to diagnose pleural effusion. During thoracoscopy, samples (biopsy) of pleura may be taken.

Pleural effusion can hinder the normal function of the lungs. Symptoms of pleural effusion include chest pain, chest heaviness, breathing difficulties, and a dry cough. Patients with malignant pleural effusions tend to be weak and have a short-span life expectancy. The prognosis depends on the type of cancer. Sixty-five percent of patients with malignant pleural effusions die within three months and 80% die within six months. However, patients with pleural effusion related to breast cancer have a longer life expectancy.

Causes

Malignant pleural effusions are most often associated with lymphomas, leukemia, breast cancer, gastrointestinal cancer, lung cancer, and ovarian cancer. For the majority of patients, pleural effusion occurs in the lung on the same side as the cancer. For one third of the patients, pleural effusion occurs in both lungs.

Pleural effusion in cancer patients can be caused by several different conditions. Blockage of the lymphatic system, a series of channels for drainage of body fluids, interferes with the removal of pleural fluid. Blockage of the veins of the lungs increases the pressure at the pleurae which causes fluid accumulation. Cancerous cells may seed onto pleurae and cause inflammation which increases fluid in the pleural space. High numbers of cancerous cells may collect in the pleural space (tumor cell suspensions) which causes extra fluid to be released. Accumulation of fluid in the abdominal cavity may cross over to the pleural space.

Treatments

Management of pleural effusion strives to relieve symptoms and improve quality of life. Cure is not always possible. The treatment method depends on the patient's age, prognosis, and location of the first tumor. Treatment for patients with pleural effusion who are asymptomatic (do not have symptoms) consists solely of observation.

Treatment options for pleural effusion include:

• Thoracentesis. Removal of the excess pleural fluid often relieves the symptoms of pleural effusion. However, effusion usually recurs within a few days. Repeat thoracentesis is not recommended, unless the patient has end-stage disease.
• Tube thoracostomy. A tube is inserted through the chest and into the pleural space to drain pleural fluid. When used alone, recurrence is very common.
• Indwelling pleural catheters. A thin flexible tube (catheter) is placed between the pleural cavity and the chest skin to allow drainage of pleural fluid. This method allows for continual drainage of pleural fluid without much pain.
• Pleurodesis. After tube thoracostomy, one of any number of chemicals (sclerosing agents) is put into the pleural space to cause the visceral and parietal pleurae to stick together. Chemical pleurodesis is considered to be the treatment of choice for patients with malignant pleural effusion.
• Pleurectomy. Surgical removal of the parietal pleura through an incision in the chest wall (thoracotomy) is nearly 100% effective. Pleurectomy is not routinely performed and is reserved for patients for whom other treatments have failed. To be eligible for pleurectomy, the patient must have a long life expectancy and be able to tolerate major surgery.
• Pleuroperitoneal shunt. This procedure places a rubber tube between the pleural space and the abdominal cavity. A pump is used to move excess fluid out of the pleural space and into the abdominal cavity, where it would be absorbed. The patient must press the pump for several minutes four times daily. Although not frequently used, this is an effective treatment for cases that failed tube thoracostomy and pleurodesis.
• External radiation. Patients who have pleural effusion caused by blockage of a lymph duct may be treated by radiation therapy. External radiation therapy is successful for patients with pleural effusion related to lymphoma.
• Supportive care. Patients with end-stage cancer may not receive treatment for pleural effusion. Pain medications and oxygen therapy can be provided to keep the patient comfortable.

—Belinda Rowland, Ph.D.

Pleural effusion
Classification and external resources
Massive left-sided pleural effusion (whiteness) in a patient presenting with lung cancer.
ICD-10	J90.-J91.
ICD-9	511.9
MeSH	D010996

Pleural effusion is excess fluid that accumulates in the pleural cavity, the fluid-filled space that surrounds the lungs. Excessive amounts of such fluid can impair breathing by limiting the expansion of the lungs during inhalation.

Contents 1 Types of fluids 2 Diagnosis 2.1 Transudate vs. exudate 3 Causes 3.1 Transudative 3.2 Exudative 3.3 Other/ungrouped 4 Treatment 5 See also 6 External links 7 References

Types of fluids

Four types of fluids can accumulate in the pleural space:

• Serous fluid (hydrothorax)
• Blood (hemothorax)
• Chyle (chylothorax)
• Pus (pyothorax or empyema)

Diagnosis

Pleural effusion is usually diagnosed on the basis of medical history and physical exam, and confirmed by chest x-ray. Chest films acquired in the lateral decubitus position (with the patient lying on his side) are more sensitive, and can pick up as little as 50 ml of fluid. At least 300 ml of fluid must be present before upright chest films can pick up signs of pleural effusion (e.g., blunted costophrenic angles). Once accumulated fluid is more than 500 ml, there are usually detectable clinical signs in the patient, such as decreased movement of the chest on the affected side, dullness to percussion over the fluid, diminished breath sounds on the affected side, decreased vocal resonance and fremitus (though this is an inconsistent and unreliable sign), pleural friction rub. Above the effusion, where the lung is compressed, there may be bronchial breathing and egophony. In large effusion there may be tracheal deviation away from the effusion.

CT scan of chest showing left sided pleural effusion. Effusion fluid often settles at the lowest space due to gravity; here at the back as the patient is lying under scanner.

Once a pleural effusion is diagnosed, the cause must be determined. Pleural fluid is drawn out of the pleural space in a process called thoracentesis. A needle is inserted through the back of the chest wall in the sixth, seventh or eighth intercostal space on the midaxillary line, into the pleural space. The fluid may then be evaluated for the following:

1. Chemical composition including protein, lactate dehydrogenase (LDH), albumin, amylase, pH and glucose
2. Gram stain and culture to identify possible bacterial infections
3. Cell count and differential
4. Cytology to identify cancer cells, but may also identify some infective organisms
5. Other tests as suggested by the clinical situation - lipids, fungal culture, viral culture, specific immunoglobulins

Transudate vs. exudate

Needle biopsy of the pleura

The third step in the evaluation of pleural fluid is to determine whether the effusion is a transudate or an exudate. Transudative pleural effusions are caused by systemic factors that alter the balance of the formation and absorption of pleural fluid (e.g., left ventricular failure, and cirrhosis), while exudative pleural effusions are caused by alterations in local factors that influence the formation and absorption of pleural fluid (e.g., bacterial pneumonia, cancer, pulmonary embolism, and viral infection).^[1]

Transudative and exudative pleural effusions are differentiated by comparing chemistries in the pleural fluid to those in the blood. According to a meta-analysis, exudative pleural effusions meet at least one of the following criteria:^[2]

1. Pleural fluid protein >2.9 g/dL (29 g/L)
2. Pleural fluid cholesterol >45 mg/dL (1.16 mmol/L)
3. Pleural fluid LDH >60 percent of upper limit for serum

Previously criteria proposed by Light for an exudative effusion are met if at least one of the following exists (Light's criteria):^[3]

1. The ratio of pleural fluid protein to serum protein is greater than 0.5
2. The ratio of pleural fluid LDH and serum LDH is greater than 0.6
3. Pleural fluid LDH is more than two-thirds normal upper limit for serum

Twenty-five percent of patients with transudative pleural effusions are mistakenly identified as having exudative pleural effusions by Light's criteria. Therefore, additional testing is needed if a patient identified as having an exudative pleural effusion appears clinically to have a condition that produces a transudative effusion. In such cases albumin levels in blood and pleural fluid are measured. If the difference between the albumin levels in the blood and the pleural fluid is greater than 1.2 g/dL (12 g/L), it can be assumed that the patient has a transudative pleural effusion^[4].

Causes

Transudative

The most common causes of transudative pleural effusions in the United States are left ventricular failure, and cirrhosis (causing hepatic hydrothorax). Pulmonary embolisms were once thought to be transudative but have been recently shown to be exudative^[5]

Exudative

Pleural effusion Chest x-ray of a pleural effusion. The arrow A shows fluid layering in the right pleural cavity. The B arrow shows the normal width of the lung in the cavity

Once identified as exudative, additional evaluation is needed to determine the cause of the excess fluid, and pleural fluid amylase, glucose, pH and cell counts are obtained.

• Pleural fluid amylase is elevated in cases of esophageal rupture, pancreatic pleural effusion, or cancer.
• Glucose is decreased with cancer, bacterial infections, or rheumatoid pleuritis.
• Pleural fluid pH is low in empyema (<7.2) and may be low in cancer.
• If cancer is suspected, the pleural fluid is sent for cytology. If cytology is negative, and cancer is still suspected, either a thoracoscopy, or needle biopsy^[6] of the pleura may be performed.
• The fluid is also sent for Gram staining and culture, and, if suspicious for tuberculosis, examination for TB markers (adenosine deaminase > 45 IU/L, interferon gamma > 140 pg/mL, or positive polymerase chain reaction (PCR) for tuberculous DNA).

The most common causes of exudative pleural effusions are bacterial pneumonia, cancer (with lung cancer, breast cancer, and lymphoma causing approximately 75% of all malignant pleural effusions), viral infection, and pulmonary embolism.

Other/ungrouped

Other causes of pleural effusion include tuberculosis (though pleural fluid smears are rarely positive for AFB, this is the most common cause of pleural effusion in some developing countries), autoimmune disease such as systemic lupus erythematosus, bleeding (often due to chest trauma), chylothorax (most commonly caused by trauma), and accidental infusion of fluids.

Less common causes include esophageal rupture or pancreatic disease, intraabdominal abscess, rheumatoid arthritis, asbestos pleural effusion, Meigs syndrome (ascites and pleural effusion due to a benign ovarian tumor), and ovarian hyperstimulation syndrome.

Pleural effusions may also occur through medical/surgical interventions, including the use of medications (pleural fluid is usually eosinophilic), coronary artery bypass surgery, abdominal surgery, endoscopic variceal sclerotherapy, radiation therapy, liver or lung transplantation, and intra- or extravascular insertion of central lines.

Treatment

The free end of the Chest Drainage Device is usually attached to an underwater seal, below the level of the chest. This allows the air or fluid to escape from the pleural space, and prevents anything returning to the chest.

Treatment depends on the underlying cause of the pleural effusion.

Therapeutic aspiration may be sufficient; larger effusions may require insertion of an intercostal drain (either pigtail or surgical). When managing these chest tubes it is important to make sure the chest tubes do not become occluded or clogged. A clogged chest tube in the setting of continued production of fluid will result in residual fluid left behind when the chest tube is removed. This fluid can lead to complications such as hypoxia due to lung collapse from the fluid, or fibrothorax, late, when the space scars down. Repeated effusions may require chemical (talc, bleomycin, tetracycline/doxycycline) or surgical pleurodesis, in which the two pleural surfaces are scarred to each other so that no fluid can accumulate between them. This is a surgical procedure that involves inserting a chest tube, then either mechanically abrading the pleura, or inserting the chemicals to induce a scar. This require the chest tube to stay in until the fluid drainage stops. This can be days to weeks and can require prolonged hospitilizations. If the chest tube becomes clogged fluid will be left behind and the pleurodesis will fail.

Pleurodesis fails in as many as 30% of cases. An alternative is to place a Pleurex or Aspira Drainage Catheter. This is a 15Fr chest tube with a one way valve. Each day the patient or care givers connect it to a simple vacuum tube and remove from 600 cc to 1000 cc. This can be repeated daily. When not in use, the tube is capped. This allows patients to be outside the hospital. For patients with malignant pleural effusions, it allows them to continue chemotherapy, if indicated. Generally the tube is in about 30 days and then it is removed when the space undergoes a spontaneous pleurodesis.

See also

• Empyema
• Heart failure
• Pulmonary embolism
• Subpulmonic effusion
• Thoracentesis

External links

• Medline Plus Article on Pleural Effusion
• Pleural Effusion Virtual Cancer Centre
• Pleural Effusion Images from MedPix

References

1. ^ Light Richard W, "Chapter 257. Disorders of the Pleura and Mediastinum" (Chapter). Fauci AS, Braunwald E, Kasper DL, Hauser SL, Longo DL, Jameson JL, Loscalzo J: Harrison's Principles of Internal Medicine, 17th Edition
2. ^ Heffner J, Brown L, Barbieri C (1997). "Diagnostic value of tests that discriminate between exudative and transudative pleural effusions. Primary Study Investigators". Chest 111 (4): 970–80. doi:10.1378/chest.111.4.970. PMID 9106577. 
3. ^ Light R, Macgregor M, Luchsinger P, Ball W (1972). "Pleural effusions: the diagnostic separation of transudates and exudates". Ann Intern Med 77 (4): 507–13. PMID 4642731. 
4. ^ Roth BJ, O'Meara TF, Gragun WH (1990). "The serum-effusion albumin gradient in the evaluation of pleural effusions". Chest 98 (3): 546–9. PMID 4642731. 
5. ^ Porcel et al Current Opinion in Pulmonary Medicine 2008, 14:337–342 PMID 18520269
6. ^ A modified outer cannula can help thoracentesis after pleural biopsy. de Menezes Lyra R. Chest. 1997 Jul;112(1):296.[1]

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