If the underlying cause of the effusion is readily apparent such as in the case of severe congestive heart failure sampling of the fluid may not be necessary however because pleural effusion may be symptomatic of a number of disease processes from benign to malignant a fluid sample is generally taken. When the doctor listens to the patient’s chest with a stethoscope normal breath sounds are muted and tapping on the chest will reveal dull rather than hollow sounds. A transudate is a clear fluid that forms not because the pleural surfaces are diseased but because of an imbalance between the normal production and removal of the fluid. The right lung is affected of the time with involvement of both lungs being seen in approximately of patients at the time of diagnosis. The most common cause of transudative fluid is congestive heart failure. Any excess fluid is absorbed by blood and lymph vessels maintaining a balance.