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 (What is a PDF document?) .

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.