Causes of Pleural Effusion

Pleural Effusion

A pleural effusion is an excess accumulation of fluid in the pleural space around the lungs. Medical ImageThe pleura are thin membranes that enclose the lungs and line the inside of the chest cavity. The 'pleural space' describes the small space between the inner and outer layers of pleura, which normally contains a small volume of lubricating pleural fluid to allow the lungs to expand without friction. This fluid is constantly being formed through leakage of fluid from nearby capillaries and then re-absorbed by the body's lymphatic system. With a pleural effusion, some imbalance between production and reabsorption of pleural fluid leads to excess fluid building up in the pleural space. There are two major types of pleural effusion :

• Transudative effusions, where the excess pleural fluid is low in protein; and
• Exudative effusions, where the excess pleural fluid is high in protein.

Causes

Anything that causes an imbalance between production and reabsorption of pleural fluid can lead to development of a pleural effusion. Medical Image Transudative pleural effusions (those low in protein) usually form as a result of excess capillary fluid leakage into the pleural space. Common causes of transudative effusions include :

• Congestive heart failure;
• Nephrotic syndrome;
• Cirrhosis of the liver;
• Pulmonary embolism; and
• Hypothyroidism.

Exudative effusions, which are high in protein, are often more serious than transudative effusions. They are formed as a result of inflammation of the pleura, which might happen for example in lung disease. Common causes of exudative effusions include :

• Pneumonia;
• Lung cancer, or other cancers;
• Connective tissue diseases, including rheumatoid arthritis and systemic lupus erythematosus;
• Pulmonary embolism;
• Asbestosis;
• Tuberculosis; and
• Radiotherapy.

Source : virtualmedicalcentre.com