Thoracentesis, also known as a pleural tap, is a procedure performed to remove excess fluid or air from your pleural space.

The pleural space is the small space between your lungs and your chest wall. A buildup of fluid in your pleural space is called pleural effusion. Pleural effusion can compress your lungs and cause difficulty breathing.

Some conditions that can cause pleural effusion include:

Thoracentesis is a minimally invasive procedure that involves inserting a needle into the pleural space around your lungs. The goal is to drain fluid or air in order to make it easier for you to breathe. In some cases, the procedure will also help your doctor discover the cause of your fluid buildup.

The amount of fluid your doctor drains depends on the underlying condition you’re dealing with. The National Heart, Lung, and Blood Institute says that it typically takes 10 to 15 minutes, but it can take longer if there’s a lot of fluid in your pleural space. After thoracentesis, a lab test called a pleural fluid analysis may be performed to figure out the cause of fluid accumulation around one or both of your lungs.

Your doctor may also perform a pleural biopsy. Though not commonly performed, it can help identify the underlying cause of pleural effusion. Potential causes include:

  • the presence of cancer cells, such as lung cancer
  • mesothelioma, which is an asbestos-related cancer of the tissues that cover your lungs
  • pleural tuberculosis

Thoracentesis can be done in a doctor’s office or in a hospital. It’s typically performed while you’re awake, but you may be sedated. You’ll need someone else to help you get home after the procedure if you’re sedated.

  1. After sitting in a chair or lying on a table, you’ll be positioned in a way that allows your doctor to access your pleural space.
  2. Your doctor should use an ultrasound to confirm the correct area where the needle will go. In some cases, they may also use CT guidance.
  3. The selected area will be cleaned and injected with a numbing agent.
  4. Your doctor will insert the needle or tube between your ribs into your pleural space. You might feel an uncomfortable pressure during this process, but try to keep very still. The excess fluid will then be drained out.
  5. Once all the fluid is drained, a bandage will be put on the insertion site.
  6. Your doctor may perform a follow-up X-ray right after the thoracentesis.
  7. Depending on the severity of your symptoms and to ensure there are no complications, they may ask you to stay overnight in the hospital or clinic to be monitored.

Thoracentesis is performed in people with pleural effusion to either improve breathing or help make a diagnosis. The American Thoracic Society says that the most common reasons to perform thoracentesis are:

  • to diagnose the cause of new pleural effusion
  • to improve comfort
  • to diagnose cancer or improve cancer symptoms
  • to diagnose a suspected infection

Your doctor can determine whether you’re a good candidate for thoracentesis.

Some people may not be able to safely undergo thoracentesis. You might not be a good candidate for thoracentesis if you have insufficient pleural fluid or a skin infection or wound at the needle insertion site.

Doctors are also cautious to perform thoracentesis on people who:

  • can’t be safely repositioned
  • have bleeding disorders
  • are taking blood thinners
  • may have scarring from recent lung surgery
  • have other conditions where potential complications outweigh benefits

There’s no special preparation for a thoracentesis. However, speak with your doctor if you have any questions or concerns about the procedure. Also, tell your doctor if you:

  • are currently taking medications, including blood thinners like aspirin, clopidogrel (Plavix), or warfarin (Coumadin)
  • are allergic to any medications
  • have any bleeding problems
  • may be pregnant
  • have lung scarring from previous procedures
  • currently have any lung diseases like asthma or emphysema

Every invasive procedure has risks, but side effects are uncommon with thoracentesis. Possible risks include:

  • pain
  • bleeding
  • bruising
  • air accumulation (pneumothorax) pushing on the lung, causing a collapsed lung
  • infection

Liver or spleen injuries are also potential complications, according to the National Heart, Blood, and Lung Institute, but they’re rare nowadays because of the use of ultrasound and CT scans.

Your doctor will go over the risks before the procedure.

Research has found that ultrasound guidance lowers the risk of complications. A 2020 study found a 1.2 percent risk of developing complications due to technical failure with ultrasound-guided thoracentesis. In comparison, there is a 10 to 18 percent risk of a collapsed lung when undergoing thoracentesis without imaging.

After the procedure is over, your doctor will monitor your vitals and may order an X-ray of your lungs. They will allow you to go home if your breathing rate, oxygen saturation, blood pressure, and pulse are all good. Most people who have a thoracentesis can go home the same day.

You’ll be able to return to most of your usual activities soon after the procedure. However, your doctor may recommend that you avoid physical activity for several days.

Your doctor will explain how to take care of the puncture site. Make sure to contact your doctor if you begin to have any signs of infection. Symptoms of infection include:

  • trouble breathing
  • coughing up blood
  • fever or chills
  • pain when you take deep breaths
  • redness, pain, or bleeding around the needle site

A thoracentesis is a minimally invasive procedure that involves a doctor removing fluid or air from the pleural space around your lungs with a needle. It’s often performed to improve breathing or help make a diagnosis.

The most common complications of thoracentesis are minor, such as bruising or bleeding at the injection site. Some people develop more severe complications like liver or spleen injuries. Your doctor can help you determine if you’re a good candidate for thoracentesis and walk you through the potential risks and benefits.