Thoracentesis is a procedure in which fluid between the chest cavity and lungs (pleural space) is collected through a needle (and sometimes a plastic catheter) inserted through the chest wall. This fluid, called pleural fluid, may then be sent to a laboratory to determine what may be causing the fluid to accumulate. Normally, only a small amount of pleural fluid is present in the pleural space. Accumulation of excess pleural fluid, or pleural effusion, can be caused by a variety of problems, including infection, inflammation, heart failure or cancer. If a large amount of fluid is present, it may prevent the complete expansion of a lung, making it difficult to breathe. The presence of fluid inside the lung cavity can be discovered during a physical examination and usually is confirmed by a chest X-ray.

Thoracentesis may be performed to:

  • Help determine the cause of fluid in the lung cavity
  • Relieve shortness of breath and pain caused by an accumulation of excess pleural fluid