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Chapters

0:00 Introduction
1:31 Causes of pleural effusion
2:46 Symptoms of pleural effusion
3:08 Diagnosis of pleural effusion
3:35 Treatment of pleural effusion





A pleural effusion is accumulation of excessive fluid in the pleural space, the potential space that surrounds each lung. Under normal conditions, pleural fluid is secreted by the parietal pleural capillaries at a rate of 0.01 millilitre per kilogram weight per hour, and is cleared by lymphatic absorption leaving behind only 5–15 millilitres of fluid, which helps to maintain a functional vacuum between the parietal and visceral pleurae. Excess fluid within the pleural space can impair inspiration by upsetting the functional vacuum and hydrostatically increasing the resistance against lung expansion, resulting in a fully or partially collapsed lung.

Various kinds of fluid can accumulate in the pleural space, such as serous fluid (hydrothorax), blood (hemothorax), pus (pyothorax, more commonly known as pleural empyema), chyle (chylothorax), or very rarely urine (urinothorax). When unspecified, the term "pleural effusion" normally refers to hydrothorax. A pleural effusion can also be compounded by a pneumothorax (accumulation of air in the pleural space), leading to a hydropneumothorax. Transudative

The most common causes of transudative pleural effusion in the United States are heart failure and cirrhosis. Nephrotic syndrome, leading to the loss of large amounts of albumin in urine and resultant low albumin levels in the blood and reduced colloid osmotic pressure, is another less common cause of pleural effusion. Pulmonary emboli were once thought to cause transudative effusions, but have been recently shown to be exudative.[2] The mechanism for the exudative pleural effusion in pulmonary thromboembolism is probably related to increased permeability of the capillaries in the lung, which results from the release of cytokines or inflammatory mediators (e.g. vascular endothelial growth factor) from the plateletrich blood clots. The excessive interstitial lung fluid traverses the visceral pleura and accumulates in the pleural space.[citation needed]

Conditions associated with transudative pleural effusions include:[3]

Congestive heart failure
Liver cirrhosis
Severe hypoalbuminemia
Nephrotic syndrome
Acute atelectasis[4]

Myxedema
Peritoneal dialysis
Meigs's syndrome
Obstructive uropathy
Endstage kidney disease