Thoracentesis (Pleural Tap)

Medically Reviewed By William C. Lloyd III, MD, FACS
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What is a thoracentesis (pleural tap)?

A thoracentesis (pleural tap) is a procedure that removes fluid from around the lungs, or pleural fluid. Your doctor may recommend a thoracentesis to diagnose and guide treatment for certain diseases, such as cancer, infections, and heart failure. 

Pleural fluid cushions and lubricates the lungs as they expand and contract with breathing. Pleural fluid is located in the pleural space, the space inside the lining that covers the lungs and inside of your chest. Certain diseases and conditions cause a buildup of pus, blood, or too much pleural fluid in the pleural space. This is called pleural effusion, which can put pressure on the lungs and make it difficult to breathe. 

A thoracentesis is only one method of diagnosing and treating pleural effusion and underlying problems. Discuss all of your testing options with your doctor to understand which options are right for you.

Why is a thoracentesis (pleural tap) performed? 

Your doctor may recommend a thoracentesis (pleural tap) to diagnose or treat pleural effusion and empyema (pronounced “em-pie-eema”). Pleural effusion is a buildup of fluid in the pleural space, inside the lining that covers the lungs and inside of the chest. Empyema is pus in the pleural space.

A thoracentesis removes fluid to make it easier for you to breathe. Your doctor may also test the fluid to determine the cause of pleural effusion or empyema. A thoracentesis helps your doctor make the best treatment decisions for underlying diseases, disorders and conditions including:

  • Heart failure, an inability of a weak heart to pump enough blood to the body. This can lead to fluid buildup.

  • Pulmonary hypertension, high pressure in the arteries that carry blood to the lungs. Pulmonary hypertension can lead to heart failure and fluid buildup.

  • Pulmonary embolism, a blood clot or other blockage in the artery that carries blood to the lungs. Pulmonary embolism can lead to heart failure, pulmonary hypertension, and fluid buildup.

  • Nephrotic syndrome, kidney damage that causes fluid buildup

  • Lung infections including pneumonia and pleurisy, which can cause inflammation of the pleural lining, fluid buildup, and sometimes pus

  • Cancer that has spread to the lung or the pleural lining. The pleural fluid is tested for cancer cells.

  • Liver disease including liver cirrhosis and liver failure, which can cause fluid buildup

Who performs a thoracentesis (pleural tap)?

The following specialists perform thoracentesis:

  • Pulmonologists specialize in the medical care of people with breathing problems and diseases and conditions of the lungs.

  • Pediatric pulmonologists specialize in the medical care of infants, children and adolescents with diseases and conditions of the lungs.

  • Hospitalists specialize in caring for hospitalized patients.

  • Critical care medicine doctors, or intensivists, care for patients with acute, life-threatening illnesses or injuries.

  • Emergency medicine doctors specialize in emergency care of people with serious and life-threatening illnesses and injuries.

How is a thoracentesis (pleural tap) performed?

Your thoracentesis will be performed in a hospital, clinic, or doctor’s office. The procedure generally takes 15 minutes and includes these steps:

  1. You will remove your clothing and dress in a patient gown.

  2. You will have an imaging test, such as an X-ray, ultrasound, or CT scan of the chest to locate the fluid and see how much fluid is around the lungs.

  3. You will sit on a chair or edge of an examination table with your arms resting on a table. You must remain very still during the entire procedure. Do not cough or breathe very deeply.

  4. Your doctor will clean the procedure area on your back with an antiseptic and place sterile drapes on your back to maintain a sterile procedure.

  5. Your doctor will inject a small amount of local anesthetic under the skin to numb the area. In some cases, you may receive a sedative to help you relax.

  6. Your doctor will insert a needle or tube into your back between the ribs and into the pleural space around the lungs. Sometimes doctors use ultrasound imaging to help place the needle in the right place.

  7. Your doctor will remove pleural fluid for testing and drain excessive pleural fluid as needed.

  8. Your doctor will remove the needle, bandage the area, and send the fluid to the laboratory for testing.

  9. Your care team will watch your vital signs closely for several hours after your thoracentesis. You will have a chest X-ray to look for complications, such as a collapsed lung (pneumothorax).

Will I feel pain?

Your comfort and relaxation is important to both you and your care team. You may feel a pinch and stinging when your doctor injects local anesthetic into you back. You may feel pressure or discomfort when the needle is inserted into your back. You may also have chest pain and an urge to cough when your doctor withdraws the pleural fluid in your chest. These sensations should be brief. 

It should be easier to breathe after your thoracentesis if your doctor drains fluid out of the pleural space. Tell your doctor or care team if any discomfort does not pass quickly or if you have any difficulty breathing after your thoracentesis.

What are the risks and potential complications of a thoracentesis (pleural tap)?  

Complications of a thoracentesis are uncommon, but any procedure involves risks and potential complications that may become serious in some cases. Complications can develop during the procedure or your recovery.

Risks and potential complications of a thoracentesis include: 

  • Adverse reaction or problems related to sedative or anesthetic medications such as an allergic reaction and problems with breathing

  • Bleeding

  • Collapsed lung (pneumothorax)

  • Infection

  • Injury to the liver or spleen, which is very rare

Reducing your risk of complications

You can reduce the risk of certain complications by following your treatment plan and: 

  • Following activity, dietary and lifestyle restrictions and recommendations before your procedure and during recovery

  • Informing your doctor or radiologist if you are nursing or if there is any possibility of pregnancy

  • Notifying your doctor immediately of any concerns, such as difficulty breathing or pain or discomfort that does not pass quickly

  • Remaining very still and not coughing or taking deep breaths during the procedure as instructed

  • Taking your medications exactly as directed

  • Telling all members of your care team if you have any allergies

How do I prepare for my thoracentesis (pleural tap)?

You are a very important member of your own healthcare team. The steps you take before your thoracentesis can improve your comfort and help obtain the most accurate test results and best treatment outcome.

There generally is no special preparation for a pleural tap, but you can get ready for your procedure by:

  • Answering all questions about your medical history, allergies, and medications. This includes prescriptions, over-the-counter drugs, herbal treatments, and vitamins. It is a good idea to carry a current list of your medical conditions, medications, and allergies at all times.

  • Learning about the procedure and asking any questions you have

  • Taking or stopping medications exactly as directed

Questions to ask your doctor

Preparing for a thoracentesis can be stressful. It is common to forget some of your questions during a doctor’s office visit. You may also think of other questions after your appointment. Contact your doctor with concerns and questions before your procedure and between appointments.

It is also a good idea to bring a list of questions to your appointments. Questions can include:

  • Why do I need a thoracentesis? Are there any other options for diagnosing or treating my condition?

  • How long will the procedure take? When will I be able to go home?

  • What restrictions will I have after the procedure? When can I return to work and other activities?

  • What kind of assistance will I need at home? Will I need a ride home?

  • When will I receive the results of my test?

  • What other tests or procedures might I need?

  • How should I take my medications?

  • How will you treat my pain?

  • When should I follow up with you?

  • How should I contact you? Ask for numbers to call during and after regular hours. 

What can I expect after my thoracentesis (pleural tap)?

Knowing what to expect after a thoracentesis can help you get back to your everyday life as soon as possible.

How will I feel after thoracentesis?

You may have mild soreness, tenderness or pain in your back after the procedure. Your doctor will prescribe a pain medication as needed. You should only take nonsteroidal anti-inflammatory drugs (NSAIDs) as directed by your doctor because people with certain conditions should not take NSAIDs. 

When can I go home?

You may go home several hours after your thoracentesis or stay in the hospital for further treatment, depending on your condition. You may need to limit your activities when you go home. Your doctor will give you specific instructions, which will vary depending on your condition and the underlying cause of pleural effusion or empyema.

When should I call my doctor?

You should keep your follow-up appointments after a thoracentesis. Contact your doctor if you have any concerns between appointments. Call your doctor right away or seek immediate medical care if you have:

  • Belly or abdominal pain

  • Bleeding

  • Chest pain

  • Difficulty breathing, such as painful breathing, coughing, shortness of breath, or difficulty taking a full breath

  • Fever (you should not have any fever after thoracentesis)

  • Leakage of fluid or blood from the injection site in the back

  • Rash or skin irritation

  • Swelling, warmth or redness from the injection site in the back

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2020 Nov 2
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
  1. Thoracentesis. American Thoracic Society.
  2. Thoracentesis. Johns Hopkins Hospital.,P07761/.
  3. What is a Thoracentesis? National Heart Lung and Blood Institute.