[Current diagnostic approach to pleural effusion].

Pleural effusion is a common pneumologic and interdisciplinary problem. Transudate/exsudate discrimination of the pleural fluid by thoracentesis remains the diagnostic basic algorithm. Regardless of a number of new markers, classical LIGHT's criteria comprising the pleural fluid protein- and LDH-values (or their serum ratio respectively) reveal the highest potency with an overall accuracy of 95 %. Expansion to cholesterol-determination (triplet test) may be helpful to identify transudates in indeterminate cases. The need for further local diagnostic evaluation is then usually restricted to exudates. Bacterial pleurisy, malignant and tuberculous effusion are the principal differential diagnoses. With the use of a variety of conventional biochemical, cytologic, immunologic and microbiologic investigations, thoracentesis will allow- or substantially narrow-diagnosis of exudates in about 70 %, with novel cell biological markers in some conditions up to 90 %. In bacterial pleurisy thoracentesis provides information directly relevant to management in terms of local interventions. It also constitutes a platform for more invasive imaging- or endoscopy-guided investigations with a focus on medical thoracoscopy (pleuroscopy). Blind needle biopsy is diagnostic in a range of 40 - 70 % both in malignancy and inflammatory disease, thoracoscopy may clarify exudative conditions in about 95 %. Thus malignancy may be specifically diagnosed in 97 % of cases, tuberculous effusion in virtually 100 %. The value of thoracoscopy is augmented by interventional options including complete evacuation of the pleural cavity, eventually followed by talc pleurodesis ("poudrage") in recurrent effusions or adhesiolysis, irrigation and fibrinolysis protocols in certain inflammatory conditions. These combined features as accomplished in local anesthesia on a remarkably high safety level characterise medical thoracoscopy as a gold standard tool for the management of pleural disease even in comparison to more elaborate surgical procedures.