Pleural effusion, sometimes called water on the lung, is a buildup of fluid between the lungs and the chest cavity. It can result from pneumonia, heart failure, cancer, and other conditions. Pleural ...

Pericarditis is inflammation of the sac around the heart, called the pericardium. If pericarditis becomes chronic, it can lead to pericardial effusion. This is when the pericardium fills with fluid.