How is pleural effusion diagnosed?

A doctor can make a preliminary diagnosis of pleural effusion by using a stethoscope to listen to the breathing sounds, as well as the sounds from tapping on the chest. The doctor may then order a chest x-ray to determine the extent of the effusion. The pleural fluid may need to be analyzed to determine the underlying cause of the pleural effusion. The fluid is taken from the lung by inserting a needle into the lungs and withdrawing the fluid. This method is called a thoracentesis .