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Also known as pleural fluid analysis, thoracentesis is a procedure that removes fluid or air from the chest through a needle or tube.


The lungs are lined on the outside with two thin layers of tissue called pleura. The space between these two layers is called the pleural space. Normally, there is only a small amount of lubricating fluid in this space. Liquid and/or air accumulates in this space between the lungs and the ribs from many conditions. The liquid is called a pleural effusion; the air is called a pneumothorax. Most pleural effusions are complications emanating from metastatic malignancy (movement of cancer cells from one part of the body to another). Most malignant pleural effusions are detected and controlled by thoracentesis. Thoracentesis is also performed as a diagnostic measure. In these cases, only small amounts of material need to be withdrawn.
Symptoms of a pleural effusion include breathing difficulty, chest pain, fever, weight loss, cough, and edema. Removal of air is often an emergency procedure to prevent suffocation from pressure on the lungs. Negative air pressure within the chest cavity allows normal respiration. The accumulation of air or fluid within the pleural space can eliminate these normal conditions and disrupt breathing and the movement of air within the chest cavity. Fluid removal is performed to reduce the pressure in the pleural space and to analyze the liquid. In addition, thoracentesis was traditionally used to remove blood from the chest cavity. This is rare now that the placement of a thoracostomy tube has proven to be a more effective and safer method.
Thoracentesis often provides immediate abatement of symptoms. However, fluid often begins to reaccumulate. A majority of patients will ultimately require additional therapy beyond a simple thoracentesis.
There are two types of liquid in the pleural space, one having more protein in it than the other. More watery liquids are called transudates; thicker fluids are called exudates. On the basis of this difference, the cause of the effusion can more easily be determined.


Thin, watery fluid oozes into the chest either because back pressure from circulation squeezes it out or because the blood has lost some of its osmotic pressure.
  • Heart failure creates back pressure in the veins as blood must wait to be pumped through the heart.
  • A pulmonary embolism is a blood clot in the lung. It will create back pressure in the blood flow and also damage a part of the lung so that it leaks fluid.
  • Cirrhosis is a sick, scarred liver that both fails to make enough protein for the blood and also restricts the flow of blood through it.
  • Nephrosis is a collection of kidney disorders that change the osmotic pressure of blood and allow liquid to seep into body cavities.
  • Myxedema is a disease caused by too little thyroid hormone.


Thicker, more viscous fluid is usually due to greater damage to tissues, allowing blood proteins as well as water to seep out.
  • Pneumonia, caused by viruses and by bacteria, damages lung tissue and can open the way for exudates to enter the pleural space.
  • Tuberculosis can infect the pleura as well as the lungs and cause them to leak liquid.
  • Cancers of many types settle in the lungs or the pleura and leak liquids from their surface.
  • Depending upon its size and the amount of damage it has done, a pulmonary embolism can also produce an exudate.
  • Several drugs can damage the lung linings as an unexpected side effect. None of these drugs is commonly used.
  • An esophagus perforated by cancer, trauma, or other conditions can spill liquids and even food into the chest. The irritation creates an exudate in the pleural space.
  • Pancreatic disease can cause massive fluid in the abdomen, which can then find its way into the chest.
  • Pericarditis is an inflammation of the sac that contains the heart. It can ooze fluid from both sides—into the heart's space and into the chest.
  • Radiation to treat cancer or from accidents with radioactive materials can damage the pleura and lead to exudates.
  • A wide variety of autoimmune diseases attacks the pleura. Among these are rheumatoid arthritis and systemic lupus erythematosus (SLE).
  • Many other rare conditions can also lead to exudates.


Blood in the chest (hemothorax) is infrequently seen outside of two conditions:
  • major trauma can sever blood vessels in the chest, causing them to bleed into the pleural space
  • cancers can ooze blood as well as fluid, they do not usually bleed massively


Occasionally, the liquid that comes out of the chest is neither transparent nor bloody, but milky. This is due to a tear of the large lymphatic channel—the thoracic duct carrying lymph fluid from the intestines to the heart. It is milky because it is transporting fats absorbed in the process of digestion. The major causes of chylothorax are:
  • injury from major trauma, such as an automobile accident
  • cancers eroding into the thoracic duct


Air in the pleural space is called pneumothorax. Air can enter the pleural space either directly through a hole between the ribs or from a hole in the lungs. Holes in the lungs are sometimes spontaneous, sometimes traumatic, and sometimes the result of disease opening a communication to the air in the lung.


Care must be taken not to puncture the lung when inserting the needle. Thoracentesis should never be performed by inserting the needle through an area with an infection. An alternative site needs to be found in these cases. Patients who are on anticoagulant drugs should be carefully considered for the procedure.


The usual place to tap the chest is below the armpit (axilla). Under sterile conditions and local anesthesia, a needle, a through-the-needle-catheter, or an over-the-needle catheter may be used to perform the procedure. Overall, the catheter techniques may be safer. Fluid or air is withdrawn. Fluid is sent to the laboratory for analysis. If the air or fluid continue to accumulate, a tube is left in place and attached to a one-way system so that it can drain without sucking air into the chest.


The location of the fluid is pinpointed through x ray or ultrasound. Ultrasound is a more accurate method when the effusion is small. A sedative may be administered in some cases but is generally not recommended. Oxygen should be given to the patient.


As long as the tube is in the chest, the patient must lie still. After it is removed, x rays will determine if the effusion or air is reaccumulating%—though some researchers and clinicians believe chest x rays do not need to be performed after routine thoracentesis.


Reaccumulation of fluid or air is a possible complications, as are hypovolemic shock (shock caused by a lack of circulating blood) and infection. Patients are at increased risk for poor outcomes if they have a recent history of anticoagulant use, have very small effusions, have significant amounts of fluid, have poor health leading into this condition, have positive airway pressure, and have adhesions in the pleural space. A pneumothorax can sometimes be caused by the thoracentesis procedure. The use of ultrasound to guide the procedure can reduce the risk of pneumothorax.
Thoracentesis can also result in hemothorax, or bleeding within the thorax. In addition, such internal structures as the diaphragm, spleen, or liver, can be damaged by needle insertion. Repeat thoracenteses can increase the risk of developing hypoproteinemia (a decrease in the amount of protein in the blood).



Abeloff, Martin D., et al., editors. Clinical Oncology. New York: Churchill Livingstone, 2000.
Celli, R. Bartolome. "Diseases of the Diaphragm, Chest Wall, Pleura and Mediastinum." In Cecil Textbook of Medicine, edited by J. Claude Bennett. Philadelphia: W. B. Saunders, 2000.


Colt, Henri G. "Factors Contributing to Pneumothorax After Thoracentesis." Chest 117 (February 2000).
Petersen, W.G. "Limited Utility of Chest Radiograph After Thoracentesis." Chest 117 (April 2000): 1038-1042.

Key terms

Axilla — Armpit.
Catheter — A tube that is moved through the body for removing or injecting fluids into body cavities.
Hypovolemic shock — Shock caused by a lack of circulating blood.
Osmotic pressure — The pressure in a liquid exerted by chemicals dissolved in it. It forces a balancing of water in proportion to the amount of dissolved chemicals in two compartments separated by a semi-permeable membrane.
Pleura — Two thin layers lining the lungs on the outside.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.


surgical puncture and drainage of the thoracic cavity; it may be done as an aid to the diagnosis of inflammatory or neoplastic diseases of the lung or pleura, or it may be used as a therapeutic measure to remove accumulations of fluid from the thoracic cavity. Called also pleurocentesis.

The procedure is done with the patient sitting up, the arms and head resting on the overbed table or over the back of a chair which the patient straddles. If unable to sit up, the patient is turned onto the unaffected side. The skin at the site of insertion of the needle is cleansed with an antiseptic, and a local anesthetic is injected. The site most often used is the seventh intercostal space, just below the angle of the scapula.

After the procedure is completed the wound usually is sealed with collodion and covered with a sterile dressing. Then a chest x-ray should be done to detect any pneumothorax. The site is checked frequently for signs of leakage. The total amount and character of the fluid obtained is noted on the patient's chart. Samples of fluid are sent to the laboratory for evaluation if requested. Immediately following the thoracentesis the patient is positioned on the unaffected side to rest the site of insertion of the trocar and allow it to seal itself. The patient is observed for signs of dizziness, changes in skin color, and respiratory and heart rate changes. Other signs of complications following thoracentesis include excessive coughing, blood-tinged sputum, and tightness of the chest.

Possible aftereffects of the procedure include pneumothorax, subcutaneous emphysema (accumulation of air in the tissues of the skin), and bacterial infection. A mediastinal shift resulting from removal of large amounts of fluid from the thoracic cavity may produce cardiac distress and pulmonary edema.
Technique of thoracentesis. The needle is advanced only as far as the pleural space.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.


Paracentesis of the pleural cavity.
[thoraco- + G. kentēsis, puncture]
Farlex Partner Medical Dictionary © Farlex 2012


Pleural fluid tap, pleurocentesis The drainage of fluid for therapeutic or diagnostic purposes from the pleural space; the fluid is obtained with a long needle, which is then analyzed for chemical composition and cell types. Cf Pericardiocentesis.
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.


Paracentesis of the pleural cavity.
Synonym(s): pleural tap, pleurocentesis, thoracocentesis.
[thoraco- + G. kentēsis, puncture]
Medical Dictionary for the Health Professions and Nursing © Farlex 2012


, thoracocentesis (tho?ra-sen-te'sis ) (?ra-ko-) [ thoraco- + centesis]
Enlarge picture
Insertion of a needle through the chest wall and into the pleural space, usually to remove fluid for diagnostic or therapeutic purposes. Synonym: pleurocentesis; thoracocentesis See: illustration

Patient care

Before the procedure, the patient is carefully examined, a history is taken, and radiological studies, such as chest x-rays or ultrasonograms, are reviewed. The procedure should be explained to the patient and sensation information provided (stinging with anesthesia instillation). The risks (bleeding, puncture of the lung with subsequent lung collapse, or introduction of infection), as well as the benefits and alternatives to the procedure, should be carefully reviewed. If the patient wishes to proceed, a consent form with the patient's signature must be completed. Allergies to local anesthetics are noted. Baseline vital signs will be obtained and supplemental oxygen administered. Cardiac monitoring is usually performed. A nurse or respiratory therapist may assist the physician and support the patient throughout the procedure. Equipment is assembled for the procedure, and, in most instances, the fluid is identified with ultrasound to avoid injury to the liver, lung, or other tissues. The patient is positioned to make pleural fluid accessible to the examiner.

The patient's skin is prepared per protocol, the area is draped, and local anesthesia is injected subcutaneously. After allowing a short time for this to become effective, the thoracentesis needle is inserted above the rib to avoid damaging intercostal vessels, which run in a neurovascular bundle beneath each rib. The patient is advised not to move, cough, or take a deep breath during the procedure to reduce the risk of injury. When the needle contacts the fluid pocket, fluid can be withdrawn by gravity drainage or with suction. When indicated after removal of the thoracentesis needle or cannula, a larger bore thoracostomy tube may be inserted to provide additional drainage.

During thoracentesis, health care professionals should assess the patient for difficulty in breathing, dizziness, faintness, chest pain, nausea, pallor or cyanosis, weakness, sweating, cough, alterations in vital signs, oxygen saturation levels, or cardiac rhythm. An occlusive dressing should be applied to the puncture site as the needle or cannula is removed, preventing air entry. The fluid obtained is labeled and sent for diagnostic tests as ordered (typically Gram stain, cultures, cell count, measurements of fluid chemistries, pH, and, when appropriate, cytology). The amount, color, and character of the fluid is documented, along with the time of the procedure, the exact location of the puncture, and the patient's reaction. After the procedure, a chest x-ray is often obtained to assess results or determine if any injury has occurred, e.g., pneumothorax. The patient should be positioned comfortably. Vital signs are monitored until stable, then as needed. The patient is advised to call for assistance immediately, if difficulty in breathing or pleuritic pain is experienced.

Medical Dictionary, © 2009 Farlex and Partners
References in periodicals archive ?
The researchers found that from 2004 to 2016, there was an increase in the proportion of all paracentesis and thoracentesis procedures performed by radiologists (70 to 80 percent and 47 to 66 percent, respectively).
Williams et al., "Simulation-Based Mastery Learning for Thoracentesis Skills Improves Patient Outcomes," Academic Medicine: Journal of the Association of American Medical Colleges, vol.
A thoracentesis of the left effusion was performed; however, cytology was negative for malignancy.
A thoracentesis was conducted, and 200 cc of purulent liquid was evacuated and further analyzed.
Diagnostic thoracentesis yielded purulent fluid with WBC 505,000 (73% segmented neutrophils, 8% lymphocytes, and 19% macrophages), RBC 0, pH 6.0, protein 3.7, LDH 41,239, and glucose 12.
Thoracentesis was performed, and 24 mL of the pleural fluid was drained, containing 95% lymphocytes; hence, a diagnosis of chylothorax was made.
Gravity assisted thoracentesis drainage was adopted institutionally.
The aim of this study is to evaluate the role of thoracic sonography in treatment of pleural effusions, concerning the type and results of different procedures (thoracentesis, chest tube, and surgery), and to identify sonographic indicators for surgical intervention (VATS or open decortication).
Patient symptoms resolved partially after he received a blood transfusion and underwent therapeutic thoracentesis. Transthoracic echocardiography revealed normal left ventricular function and a large, mobile, cystic mass in the right and left atrium.
He had 12 paracenteses in 2015 and starting from February 2016 was undergoing thoracentesis 3 times weekly (about 8-9 liters/week) and a single weekly paracentesis up to 5 liters.
The literature provides many options including antibiotics alone or in combination with repeated thoracentesis, closed intercostal tube drainage, fibrinolytic agents like streptokinase or deoxyribonuclease, video-assisted thoracoscopy, thoracotomy and decortication.