Test Overview
Thoracentesis is a procedure to remove fluid from the space between the lungs and the chest wall called the pleural space. It is done with a needle (and sometimes a plastic catheter) inserted through the chest wall. This pleural fluid may be sent to a lab to determine what may be causing the fluid to accumulate in the pleural space.
Normally only a small amount of pleural fluid is present in the pleural space. Accumulation of excess pleural fluid (pleural effusion) may be caused by many conditions, such as infection, inflammation, heart failure, or cancer. If a large amount of fluid is present, it may be difficult to breathe. Fluid inside the pleural space may be found during a physical examination and is usually confirmed by a chest X-ray.
Why It Is Done
Thoracentesis may be done to:
- Determine the cause of excess pleural fluid (pleural effusion).
- Relieve shortness of breath and pain caused by a pleural effusion.
How To Prepare
You will be asked to sign a consent form before a thoracentesis. Talk to your doctor about any concerns you have regarding the need for the procedure, its risks, how it will be done, or what the results will indicate. To help you understand the importance of this procedure, fill out the medical test information form .
Tell your doctor if you:
- Are taking any medications.
- Have allergies to any medications, including anesthetics.
- Have any bleeding problems or take blood thinners, such as aspirin or warfarin (Coumadin).
- Are or might be pregnant.
Also, certain conditions may increase the difficulty of thoracentesis. Let your doctor know if you have:
- Had lung surgery. The scarring from the first procedure may make it difficult to do this procedure.
- A long-term (chronic), irreversible lung disease, such as emphysema.
A chest X-ray is usually done before the procedure. Your doctor may order certain blood tests, such as a complete blood count (CBC) and bleeding factors, before your procedure.
How It Is Done
This procedure may be done in your doctor's office, in the X-ray department of a hospital, in an emergency room, or at your bedside in the hospital. Your doctor may have a nurse assist with the procedure.
You will need to take off all or most of your clothes (you may be allowed to keep on your underwear if it does not interfere with the procedure). You will be given a cloth or paper covering to use during the procedure. During the procedure, you will be seated but leaning forward on a padded bedside table. If your test is done in the X-ray department, X-rays or an ultrasound may be used to confirm the location of fluid in your chest.
The needle site between your ribs will be cleaned with an antiseptic solution. Your doctor will give you a local anesthetic in your chest wall so you won't feel any pain when the longer needle that withdraws the fluid is inserted. Once the area is numb, your doctor will insert the needle to where the fluid has collected (pleural space). You may feel some mild pain or pressure as the needle enters the pleural space.
A syringe or a small tube attached to a vacuum bottle is used to remove the pleural fluid. Your doctor collects 50mL(1.5fl oz) to 100mL(3fl oz) of fluid at a time to send to the lab. Up to 1500mL(50fl oz) may be removed if the fluid is making it difficult for you to breathe. Once the fluid is removed, the needle or small tube is removed and a bandage is put on the site.
An X-ray is usually taken right after the procedure to make sure that no complications have occurred. If more pleural fluid collects and needs to be removed, another thoracentesis may be done later.
This procedure takes about 10 to 15 minutes.
How It Feels
When you are given the shot to numb your skin at the needle site, you will feel a sharp stinging or burning sensation that lasts a few seconds. When the needle is inserted into the chest wall, you may again feel a sharp pain for a few seconds.
When the pleural fluid is removed, you may feel a sense of "pulling" or pressure in your chest. Tell your doctor or nurse if you feel faint or if you have any shortness of breath, chest pain, or uncontrollable cough.
If a large amount of pleural fluid was removed during the procedure, you will probably be able to breathe more easily.
Risks
Thoracentesis is generally a safe procedure. A chest X-ray is usually done right after the procedure to make sure that no complications have occurred. Complications may include:
- A partial collapse of the lung (pneumothorax). This may occur if the needle used to remove the pleural fluid punctures the lung, allowing air to flow into the pleural space.
- Pulmonary edema, which may occur if a large amount of fluid is removed.
- Infection and bleeding.
- Damage to the liver or spleen, though this is rare.
Results
Thoracentesis is a procedure to remove fluid from the space between the lungs and the chest wall called the pleural space. Results from a lab are usually available in 1 to 2 working days. If the fluid is being tested for an infection, such as tuberculosis, results may not be available for several weeks.
Thoracentesis
| Normal: |
A small amount of clear, colorless, or pale yellow pleural fluid, usually less than 20mL(0.7fl oz), is normally present. No infection, inflammation, or cancer is found. |
| Abnormal: |
A large amount of pleural fluid is present. |
Fluid may be labeled as either a transudate or an exudate. The difference between these two types of fluid has to do with the amount of protein and other substances found in the fluid.
- A transudate has a low white blood cell (WBC) count, a low lactate dehydrogenase (LDH) enzyme level, and a low protein level. A transudate may be caused by cirrhosis, heart failure, or nephrotic syndrome.
- An exudate may be caused by diseases, such as infection (pneumonia), chest injury, cancer, pancreatitis, autoimmune disease, or a pulmonary embolism (PE).
- If an infection is present, the exudate will have a high WBC count, a high LDH enzyme level, a high protein level, and bacteria or other infectious organisms.
- If cancer is present, the exudate will have a high WBC count (often lymphocytes), a high LDH enzyme level, and a high protein level. Abnormal cells may also be present.
- If a pulmonary embolism is present, the exudate will have a low WBC count and large numbers of red blood cells. The protein level for a PE may be high or low.
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What Affects the Test
Factors that can interfere with your procedure or the accuracy of the results include:
- Use of antibiotics.
- The inability to remain still.
What To Think About
- Thoracentesis may not be done for people who have:
- A bleeding disorder.
- Heart failure or enlargement of the right side of the heart (cor pulmonale).
- A pleural biopsy may be done at the same time as a thoracentesis to collect a sample of tissue from the inner lining of the chest wall.
- Thoracentesis may be done before another procedure called pleurodesis. During this procedure, a chemical or medication (talc or doxycycline) is put into the pleural space, which triggers an inflammatory reaction over the surface of the lung and inside the pleural space. This in turn causes the layer of pleura attached to the lung to stick to the layer of pleura on the inside of the chest wall. This takes away the space between the pleura and prevents or reduces the collection of more pleural fluid. Pleurodesis may be done when fluid collects in the chest more than one time.
References
Other Works Consulted
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Chernecky CC, Berger BJ, eds. (2004). Laboratory Tests and Diagnostic Procedures, 4th ed. Philadelphia: Saunders.
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Fischbach FT, Dunning MB III, eds. (2004). Manual of Laboratory and Diagnostic Tests, 7th ed. Philadelphia: Lippincott Williams and Wilkins.
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Pagana KD, Pagana TJ (2006). Mosby’s Manual of Diagnostic and Laboratory Tests, 3rd ed. St. Louis: Mosby.
Credits
| Author |
Maria G. Essig, MS, ELS |
| Editor |
Susan Van Houten, RN, BSN, MBA |
| Associate Editor |
Tracy Landauer |
| Primary Medical Reviewer |
Caroline S. Rhoads, MD
- Internal Medicine |
| Specialist Medical Reviewer |
Robert L. Cowie, MB, FCP(SA), MD, MSc, MFOM
- Pulmonology |
| Last Updated |
March 21, 2007 |
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