Thoracentesis is a medical procedure used to remove excess fluid from the space between the lungs and the chest wall, known as the pleural space. This fluid buildup can cause difficulty in breathing and may be due to various conditions, such as pneumonia, heart failure, or cancer. During the procedure, a healthcare provider uses a needle to carefully extract the fluid for analysis and to relieve pressure on the lungs. The procedure is typically performed in a hospital or clinic setting and may involve the use of ultrasound to guide the needle placement. Patients may experience some discomfort, but it is generally quick and can provide significant relief. After the fluid is removed, it is sent to a laboratory for testing to help determine the underlying cause of the fluid accumulation.