Red blood cell counts are elevated in cases of bloody effusions (for example after heart surgery or hemothorax from incomplete evacuation of blood).
When a pleural effusion has been determined to be exudative, additional evaluation is needed to determine its cause, and amylase, glucose, pH and cell counts should be measured. The B arrow shows the normal width of the lung in the cavity The A arrow shows fluid layering in the right pleural cavity. Pleural effusion Anteroposterior Chest X-ray of a pleural effusion. Ĭonditions associated with transudative pleural effusions include: The excessive interstitial lung fluid traverses the visceral pleura and accumulates in the pleural space. vascular endothelial growth factor) from the platelet-rich blood clots. 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. Pulmonary emboli were once thought to cause transudative effusions, but have been recently shown to be exudative. 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. The most common causes of transudative pleural effusion in the United States are heart failure and cirrhosis. A pleural effusion can also be compounded by a pneumothorax (accumulation of air in the pleural space), leading to a hydropneumothorax. When unspecified, the term "pleural effusion" normally refers to hydrothorax. 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). 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. Under normal conditions, pleural fluid is secreted by the parietal pleural capillaries at a rate of 0.6 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. A pleural effusion is accumulation of excessive fluid in the pleural space, the potential space that surrounds each lung.
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