Excess of fluid surrounding the lungs in between the layers of the pleura is called pleural effusion.

Pleura is a protective layer covering the lungs. The pleura is a double membrane that is a large, thin sheet of tissue that wraps around the lung’s exterior and lines the inside of the chest cavity.

There is usually a small trace amount of fluid inside the pleural space; however, if there is excess fluid, it becomes more difficult to breathe due to the inability of the lungs to fully inflate, which ultimately causes a shortness of breath and pain.

Pleural effusions are very common, with approximately 100,000 cases diagnosed in the United States each year, according to the National Cancer Institute.


Depending on the cause, the excess fluid may be either protein-poor (transudative) or protein-rich (exudative). These two categories help physicians determine the cause of the pleural effusion.

There are various causes for the pleural effusion, some are minor not requiring any treatment and which subside on their own while others require tests, analysis of the fluid for better characterization. Based on the amount and causes, some of these definitive management either by drainage or placement of tubs to facilitate drainage.

This document is meant to discuss the procedure process. Please refer to other sources if information needed in regards to the causes, tests involved.


A minimally invasive procedure to drain fluid or air that is surrounding the lungs. It allows obtaining a sample of the pleural fluid, which can help determine the etiology.

Though this procedure can be done blindly, with so much advancements in radiology, its safer to perform the procedure under ultrasound guidance.

A small catheter or needle is inserted through the chest wall into the pleural space, a small area between the pleura (thin covering that protects and cushions the lung) and the inner chest wall and lung.


This can be performed with the patient in multiple positions, like sitting up or lying flat depending on what’s the best position to drain maximum fluid.

This is a low risk procedure which can be performed with local anesthetic to numb the area of entry. A local anesthetic will be injected in the selected area where the needle or catheter (in some cases) will be inserted to withdraw the fluid into a bottle or a bag.

This procedure takes about 10 to 15 minutes depending on the amount of fluid in the pleural space. Depending on the amount of fluid, all fluid might not be drained as too much fluid drainage might cause more reaccumulation within a shorter period leading to more interventions or hospital admissions.

Though thoracentesis is considered a low-risk procedure, there are few potential risks involved which include bleeding as there are blood vessels in the adjacent vicinity, infection due to skin breach, liver/spleen injury (rare) which is due to technical problems, and the lungs can collapse due to air entry into the pleural space which is called pneumothorax.

Most of these are managed accordingly for example, pneumothorax requires a chest tube placement to drain the air, bleeding might be controlled with manual compression, in rare situations might require an angiogram or surgery.

What is Thoracentesis?

Removal of excess fluid (known as pleural effusion) from the pleural space (the space between the outside of the lungs and the inside of the chest wall).

Why do I need thoracentesis?

Most patients with excess fluid present with difficulty in breathing. This procedure allows easier breathing and also the fluid can be sent to the lab for testing to determine the cause for the excess fluid.

What causes pleural effusion?

There are numerous causes for pleural effusion; some may be minor with no treatment required while other may require tests, analysis of fluid for better comprehension. Depending on quantity of fluid and its cause, some cases prompt definitive management either through drainage or by by placement of tubes to provoke drainage.

Why do I have excess fluid in my lungs?

Conditions including lung infections, congestive heart failure, renal failure and tumors can cause excess fluid. These are various other reasons which could cause excess fluid. Please consult your doctor or other sources to know more about the causes of excess fluid.

How long does this procedure take?

Approximately 10-15 min depending upon the amount of fluid in the pleural space.

How is the procedure performed?

This procedure can be performed with local anesthesia, few people require more than local anesthesia. Patients are positioned either in sitting up or to the side or in supine position. They are positioned to get a best position to drain maximum fluid. Following a local anesthetic to numb the area, a needle or catheter (in some cases) will be inserted under ultrasound guidance to withdraw the fluid into a bottle or bag.

What occurs after thoracentesis?

Post thoracentesis, the needle or catheter are removed. Sterile dressing applied. Patients are transferred to recovery room for observation. If vitals are stable, they can be discharged.

Who performs this procedure?

This procedure is better performed by interventional radiologists, who use ultrasound guidance to perform this procedure. In difficult cases, CT guidance can be used to guide the procedure. Some clinicians who are experienced can also perform this procedure at the office

What are the benefits of this procedure?

Generally a safe procedure with no surgical incision. Fluid removal eases breathing and also the fluid can be sent for testing to find the cause.

What are the risks associated with this procedure?

Though this is a safe procedure, a few risks are associated. While performing the procedure, air can enter the pleural space from outside causing collapse of the lung (Pneumothorax). Most of the times, this resolves on its own. Very rarely, there is a need for placement of a chest tube to suck the air out otherwise the lungs get collapsed and cause breathlessness.
Other risks which are minor include bleeding, pain.
Other rare risks include liver/spleen injury which are more related to the technique.

How can these risks be addressed?

Like explained above, Pneumothorax resolves on its own for most of the times, If large or does not resolve, then there is a need for placement of a chest tube to suck the air out otherwise the lungs get collapsed and cause breathlessness.
Bleeding can be managed mostly by compression. Very rarely, the bleeding is severe requiring intervention either by performing angiogram or surgery.
Other rare risks include liver/spleen injury which are more related to the technique.