Pleural effusion overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Template:GCC
Overview
Pleural effusion is the presence of excessive fluid in the pleural cavity resulting from transudation or exudation from the pleural surfaces.
In normal conditions, the pleural space contains a small amount of fluid (≈0.3 mL·kg-1) maintained by a complex interplay of hydrostatic pressures and lymphatic drainage, which allows for steady liquid and protein turnover.[1] Pathological processes may lead to the development of pleural effusions by causing disequilibrium between the rates of pleural fluid formation, pleural permeability and pleural fluid absorption.
Four types of fluids can accumulate in the pleural space:
- Serous fluid (hydrothorax)
- Blood (hemothorax)
- Chyle (chylothorax)
- Pus (pyothorax or empyema)
Pathophysiology
Healthy individuals have less than 15 ml of fluid in each pleural space. Normally, fluid enters the pleural space from the capillaries in the parietal pleura, from interstitial spaces of the lung via the visceral pleura, or from the peritoneal cavity through small holes in the diaphragm. This fluid is normally removed by lymphatics in the visceral pleura, which have the capacity to absorb 20 times more fluid than is normally formed. When this capacity is overwhelmed, either through excess formation or decreased lymphatic absorption, a pleural effusion develops.
Treatment
Physical Examination
Once accumulated fluid is more than 500 ml, there are usually detectable clinical signs in the patient, such as decreased movement of the chest on the affected side, dullness to percussion over the fluid, diminished breath sounds on the affected side, decreased vocal fremitus and resonance, pleural friction rub, and egophony.