Patients are often referred to the office because of fluid accumulation in the chest. This accumulation is referred to as a pleural effusion. Many patients think that the fluid has accumulated in their lungs and are surprised to find that the fluid is in the chest cavity. The most common question is how did the fluid get there. Usually, there are only a few milliliters of fluid in each side of the chest.

The fluid is produced by the inner lining of the chest wall and absorbed by the covering of the lungs. The fluid is carried away by the lymphatic system and then placed back into the blood stream.

Assuming that there has been no trauma to the chest or other obvious reasons for fluid to be in the chest, then the reason for fluid accumulation is either more fluid production or less absorption. Many times, it is easy to decide why fluid has accumulated in the chest but often it is not.

Removing some or all the fluid and then checking for cells in the fluid, or the presence of bacteria or certain proteins can help find the reasons for accumulated fluid. It should be obvious that knowing the cause helps to guide therapy.

Fluid is removed from the chest cavities by a process called thoracentesis. A local anesthetic is applied and a small tube is inserted into the chest and some or all of the fluid is removed and sent to the lab for analysis.