ABSTRACT
Diagnostic thoracentesis has been performed for more than 150 years and remains the first step to take in the evaluation of a pleural effusion of unknown origin (1). Thoracentesis can be combined with closed needle pleural biopsy, a procedure first described in 1955 and refined thereafter (2). The analysis of pleural fluid offers the opportunity to diagnose the underlying disease directly, or provides valuable information for narrowing the spectrum of possible causes. Moreover, pleural fluid findings may precipitate immediate therapeutic steps in parapneumonic effusions or empyema. Closed needle biopsy, although less often practiced nowadays, is of importance in tuberculosis (tb) pleurisy, and pleural malignancy. Diagnostic thoracentesis as well as closed needle biopsy are simple and straightforward procedures, and severe complications are rare. This chapter will discuss the technique, indications and contraindications, yield, complications and limitations of each method. Slight overlap with other chapters may occur where diagnostic yields are dealt with, and the reader is kindly asked to consult the relevant chapters for in-depth information about specific diseases. \
II.Indications, Contraindications
A.Diagnostic Thoracentesis
Diagnostic pleurocentesis to obtain up to 50 mL of pleural fluid is indicated in almost all patients with pleural effusion of unknown origin. If a pleural effusion can be explained by a known medical condition with a high degree of certainty, a watchful waiting strategy may be endorsed. The same is true for expected transudative effusions, since their diagnostic value is limited. In all instances where an exudative effusion is likely, analysis of a pleural effusion offers an excellent opportunity to diagnose the underlying disease. In a series of 129 consecutive patients, a definitive diagnosis could be made in 18% of cases with pleural fluid analysis, and a presumptive diagnosis in up to 75% of cases when correlated with clinical findings. Moreover, previously suspected diseases could be excluded in many cases (3).
