[Laboratory diagnostics of pleural effusion].

Pleural effusion is a frequent reason for a pulmonologist's investigation. Many pulmonary and extrapulmonary causes of pleural effusion exist. Heart failure, pneumonia and malignancies are the most frequent among them. Laboratory examination of pleural liquid is a corner stone of diagnostics. We use various biochemical, microbiological, cytologic and other methods. The first step is a differentiation between transudate and exudate. If the laboratory examinations are unsuccessful, we can use invasive procedures - pleural biopsy and thoracoscopy. Despite all modern diagnostic methods the causes of about 15% pleural effusions remain unclear.