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ironman · 04-22-2003, 03:29 PM

Differentiation of Exudates from Transudates

A transudative pleural effusion occurs when pleural fluid accumulates because of an imbalance between the hydrostatic and oncotic pressures. The leading causes of transudative pleural effusions are congestive heart failure, cirrhosis, and pulmonary embolism. In contrast, an exudative pleural effusion occurs when the local factors influencing the accumulation of pleural fluid are altered. The leading causes of exudative effusions are pneumonia, cancer, and pulmonary embolism.

The first step in the evaluation is to determine whether an effusion is transudative or exudative.6 If it is exudative, more diagnostic tests are required in order to determine the cause of the local disease, whereas if it is transudative, the physician must establish or rule out a diagnosis of congestive heart failure, cirrhosis, or pulmonary embolism.

For the past several decades, transudates have been differentiated from exudates according to Light's criteria,7 by measurement of the levels of protein and lactate dehydrogenase in the pleural fluid and in the serum (Table 3). Since these criteria were originally published, several alternative measurements have been proposed for making this distinction8,9 (Table 3). Light's criteria are the most sensitive for identifying exudates but have lower specificity than other criteria — that is, on the basis of Light's criteria, some patients who actually have transudative pleural effusions will be thought to have exudative pleural effusions. If the clinical appearance suggests a transudative effusion but the pleural fluid is an exudate according to Light's criteria, the difference between the albumin levels in the serum and the pleural fluid should be measured. Almost all patients with a serum albumin level that is more than 1.2 g per deciliter higher than the pleural-fluid albumin level have a transudative effusion.9 However, this albumin gradient alone should not be used to distinguish transudates from exudates because it will misidentify approximately 13 percent of exudates as transudates.9

04-22-2003, 03:29 PM	#133 (permalink)
ironman Smithers, release the hounds Location: Guatemala, Guatemala	Differentiation of Exudates from Transudates A transudative pleural effusion occurs when pleural fluid accumulates because of an imbalance between the hydrostatic and oncotic pressures. The leading causes of transudative pleural effusions are congestive heart failure, cirrhosis, and pulmonary embolism. In contrast, an exudative pleural effusion occurs when the local factors influencing the accumulation of pleural fluid are altered. The leading causes of exudative effusions are pneumonia, cancer, and pulmonary embolism. The first step in the evaluation is to determine whether an effusion is transudative or exudative.6 If it is exudative, more diagnostic tests are required in order to determine the cause of the local disease, whereas if it is transudative, the physician must establish or rule out a diagnosis of congestive heart failure, cirrhosis, or pulmonary embolism. For the past several decades, transudates have been differentiated from exudates according to Light's criteria,7 by measurement of the levels of protein and lactate dehydrogenase in the pleural fluid and in the serum (Table 3). Since these criteria were originally published, several alternative measurements have been proposed for making this distinction8,9 (Table 3). Light's criteria are the most sensitive for identifying exudates but have lower specificity than other criteria — that is, on the basis of Light's criteria, some patients who actually have transudative pleural effusions will be thought to have exudative pleural effusions. If the clinical appearance suggests a transudative effusion but the pleural fluid is an exudate according to Light's criteria, the difference between the albumin levels in the serum and the pleural fluid should be measured. Almost all patients with a serum albumin level that is more than 1.2 g per deciliter higher than the pleural-fluid albumin level have a transudative effusion.9 However, this albumin gradient alone should not be used to distinguish transudates from exudates because it will misidentify approximately 13 percent of exudates as transudates.9 __________________ If I agreed with you we´d both be wrong