Thoracentesis

Test Overview

Thoracentesis (say "thor-uh-sen-TEE-sis") is a procedure to remove fluid from the space between the lungs and the chest wall. This is called the pleural space. The procedure may also be called a "chest tap."

It is normal to have a small amount of fluid in the pleural space. But too much fluid can build up because of problems such as infection, heart failure, and lung cancer. The procedure may be done to help with shortness of breath and pain caused by the fluid buildup. Or you may have it done so the doctor can test the fluid to find the cause of the buildup.

Your doctor will put a long, thin needle or a thin plastic tube, called a catheter, between two of your ribs. The doctor will use the needle or catheter to take fluid out.

You may get medicine before the procedure. This helps with pain and helps you relax. The procedure will take about 15 minutes. Most people go home shortly after. You can go back to work or your normal activities as soon as you feel up to it.

If the doctor sends the fluid to a lab for testing, it usually takes a few hours to get the results. Some of the test results may take a few days. The doctor or nurse will discuss the results with you.

Why It Is Done

Thoracentesis may be done to:

  • Find the cause of excess pleural fluid (pleural effusion).
  • Relieve shortness of breath and pain caused by a pleural effusion.

How To Prepare

Procedures can be stressful. This information will help you understand what you can expect. And it will help you safely prepare for your procedure.

Preparing for the procedure

  • Be sure you have someone to take you home. Anesthesia and pain medicine will make it unsafe for you to drive or get home on your own.
  • Understand exactly what procedure is planned, along with the risks, benefits, and other options.
  • Tell your doctor ALL the medicines, vitamins, supplements, and herbal remedies you take. Some may increase the risk of problems during your procedure. Your doctor will tell you if you should stop taking any of them before the procedure and how soon to do it.
  • If you take aspirin or some other blood thinner, ask your doctor if you should stop taking it before your procedure. Make sure that you understand exactly what your doctor wants you to do. These medicines increase the risk of bleeding.
  • Make sure your doctor and the hospital have a copy of your advance directive. If you don't have one, you may want to prepare one. It lets others know your health care wishes. It's a good thing to have before any type of surgery or 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.

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 locate the 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. When 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.

Your doctor will use a syringe to remove a sample of fluid. If larger amounts of pleural fluid are removed, a small tube attached to a vacuum bottle is used. Your doctor will send the fluid to the lab. After the fluid is removed, the needle or small tube is removed. Then a bandage is put on the site.

After the test

An X-ray may be taken right after the procedure to make sure that no complications have occurred.

How long the test takes

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.

Risks

Thoracentesis is generally a safe procedure. A chest X-ray may be done right after the procedure to make sure that no complications have occurred. Complications may include:

  • A partial collapse of the lung (pneumothorax).
  • Fluid buildup in the lung.
  • Infection.
  • Bleeding.
  • Damage to another organ, such as the liver or spleen.

Results

Results from a lab are usually ready in 1 to 2 working days. If the fluid is being tested for an infection, such as tuberculosis, results may take several weeks.

Thoracentesis

Normal:

A small amount of clear, colorless, or pale yellow pleural fluid, usually less than 20 mL (0.7 fl 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.

  • 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.

Credits

Current as of: October 26, 2020

Author: Healthwise Staff
Medical Review:
Adam Husney MD - Family Medicine
E. Gregory Thompson MD - Internal Medicine
David C. Stuesse MD - Cardiac and Thoracic Surgery