Bilateral pleural effusions of less than 500 milliliters are generally referred to clinically as small pleural effusions. It can be categorized into exudative pleural effusion and leaky pleural effusion.
The pleural cavity is a potential cavity surrounded by the visceral pleura and the mural pleura, in which there is normally about 5-15 ml of fluid, which plays a lubricating role when performing respiratory movements. If a small amount of fluid is found in both thoracic cavities by examination, it may be related to pathologic factors, such as exudative changes in the thoracic cavity caused by pulmonary infection.
Bilateral pleural effusion increases in small amounts and is either exudative or leaky. Exudative can be seen in lung infections, connective tissue disease, and malignant tumors of the lungs and pleura. Possible causes of leaky pleural effusion are congestive heart failure, constrictive pericarditis, and cirrhosis. If a small amount of pleural effusion is present bilaterally it is recommended to seek medical attention to find the cause and treat the cause under the guidance of the doctor.