How to Assess a Patient with Pleural Effusion

Pleural effusion (PE) is the accumulation of fluid in the pleural cavity which lies between the visceral and parietal pleura. The type of pleural fluid can be exudative or transudative and can be categorised using Lights criteria. Exudative pleural effusions are due to increased mesothelial and capillary permeability or impaired lymphatic drainage, most commonly due to pneumonia. Transudative effusions are due to raised hydrostatic pressures, for example secondary to congestive cardiac failure or liver cirrhosis. Investigating a pleural effusion is vital to enable identification of the underlying cause. Investigation can include imaging, blood tests and/or a diagnostic tap to enable examination of pleural fluid for biochemistry, malignant cells, cultures and AFB. Once the underlying cause has been understood, definitive treatment can commence. In essence, this comprehensive review provides clinicians with a nuanced understanding of PE evaluation and management, facilitating informed decision-making and optimised patient care.