A thoracentesis is used to determine the cause of a pleural effusion or to relieve symptoms caused by a pleural effusion, such as shortness of breath. A pleural effusion can be caused by many different conditions, including infections, inflammatory, malignant, and non-inflammatory. By examining the fluid and the types of cells it contains, the cause of the effusion can usually be determined.
Before a thoracentesis, a chest x-ray and/or chest ultrasound is taken to identify the location of the pleural effusion. The procedure takes a short time and can be performed at a patient's bedside or in a physician's office.
A thoracentesis involves the following steps:
- The patient is asked to sit upright during the procedure. It is important to remain still during the procedure so that the fluid does not shift.
- The skin is cleaned with an antibacterial solution in the area where the needle will be inserted.
- A small amount of numbing medicine (a local anesthetic) is injected into the area. This medicine helps minimize discomfort during the procedure.
- A slightly larger needle is inserted in the same location. A syringe is attached to this needle and is used to withdraw fluid from around the lung.
- The needle is removed and pressure is briefly applied to the insertion site.
In most cases, a thoracentesis is performed without complications. Most complications that occur are minor and resolve on their own or are easily treated. Potential complications include the following:
- Pain - Some discomfort may occur when the needle is inserted. Pain generally resolves once the needle is removed.
- Bleeding - Bleeding is usually minor and stops on its own. Rarely major bleeding around the lung may occur, requiring drainage or surgery.
- Infection - The risk of infection is low.
- Pneumothorax or collapsed lung - Occasionally (ten percent of the time), the needle used to obtain a fluid sample can puncture the lung. Most of the times, such a puncture is small and only requires observation. If large, then it would require a chest tube to drain the air and allow the lung to re-expand.
- Liver or spleen puncture - In very rare cases, the liver or spleen may be punctured during thoracentesis. Sitting upright and remaining still during the procedure helps to keep the liver and spleen away from the insertion area and minimizes the risk of this complication.
Following the Procedure
After the procedure, the doctor will observe the insertion site for signs of bleeding and assess breathing for signs of lung collapse (pneumothorax). A chest x-ray will be obtained to assess for lung expansion and exclude the presence of a pneumothorax. The doctor will examine the fluid, particularly its color and consistency, and will also send the fluid for laboratory tests.