胸腔积液的病因和形成机制有多种。当确定了胸液的存在后，还必须尽快明确病因才能进行针对性治疗。为减少弯路，缩小鉴别诊断范围，尽快确诊，一般均首先将其分为渗出液和漏出液两类。首先两者形成机制不同，渗出液是由于胸膜毛细血管通透性增高（如各种炎症、肿瘤浸润等使毛 Pleural effusion etiology and formation of a variety of mechanisms. After determining the existence of pleural fluid, but also must be clear as soon as possible the cause of the disease for targeted treatment. To reduce detours, reduce the scope of differential diagnosis, diagnosed as soon as possible, are generally the first to be divided into two types of exudate and leakage of fluid. First of all, the formation of the two different mechanisms, exudate is due to increased pleural capillary permeability (such as various inflammation, tumor infiltration so hair