Pleural fluid analysis is the analysis of pleural fluid in the laboratory that occurs after a pleural tap, or thoracentesis. A thoracentesis is a procedure used to drain excess fluid from the space outside of the lungs but inside the chest cavity. Normally, this area contains about 20 milliliters of clear or yellow fluid. If there’s excess fluid in this area, it can cause symptoms such as shortness of breath and coughing. An excess of pleural fluid, known as pleural effusion, will show up on a chest X-ray, CT scan, or ultrasound. Your doctor will perform a thoracentesis by inserting a hollow needle or catheter into the space between two ribs in your back. This space between two ribs is called the intercostal space. The procedure typically takes place under local anesthesia. Once your doctor has drained the excess fluid, they’ll send it to the laboratory to determine the contents of the fluid and likely cause of the fluid buildup. Thoracentesis is performed under local anesthetic by a doctor in a hospital or same-day surgery setting. Before the procedure, you can expect to have a chest X-ray, a CT scan, or an ultrasound of your chest. Blood tests are used to confirm that your blood is clotting normally. Thoracentesis can be done during a hospital stay or as an outpatient procedure, meaning you can go home afterward. When you arrive for the procedure, you’ll be asked to change into a hospital gown. You’ll sit on the edge of an armless chair or on a bed. A technician will help you lean forward so that your arms and head rest on a small table in front of you. It’s important to remain as still as possible during the procedure. The technician will cleanse the skin of your side and back with an antiseptic, which may feel cold. Your doctor will check the preparations and give you an injection of a local anesthetic. You can expect the injection to sting, but only for a short while. A small area of your back, between your ribs, will become numb. After the area is numb, your doctor will insert a hollow needle between your ribs so that the excess fluid can drain into collection bottles. As the fluid drains, you may experience some discomfort or a strong urge to cough. The procedure typically takes about 15 minutes to complete.