Your doctor will send the fluid removed during thoracentesis for testing. The fluid will be checked for signs of heart failure, infection, cancer, or other conditions that may cause a pleural effusion (the buildup of fluid between the lungs and chest wall).
Once the cause of the pleural effusion is known, your doctor will talk to you about a treatment plan. For example, if an infection is the cause, you may need antibiotics to fight the infection. If the cause is heart failure, you'll be treated for that condition.