pulmonary disorders
Pleural Effusion
Etiology of Pleural Effusion
Pleural effusions are usually categorized as Transudates Exudates Categorization of the effusions is based on laboratory characteristics of the fluid (see table). Whether unilateral or bilateral, a transudate can usually be treated without extensive evaluation, whereas the cause of an exudate requires investigation. There are numerous (> 50) causes (see table). are caused by some combination of increased hydrostatic pressure and decreased plasma oncotic pressure. Heart Failure (HF) is the most common cause, followed by are caused by local processes that lead to increased capillary permeability, resulting in exudation of fluid, protein, cells, and other serum constituents. Causes are numerous; the most common are Overview of Pneumonia , cancer, Yellow nail syndrome is a rare disorder causing chronic exudative pleural effusions, lymphedema, and dystrophic yellow nails—all thought to be the result of impaired lymphatic drainage. Chylous effusion(chylothorax) is a milky white effusion high in triglycerides caused by traumatic or neoplastic (most often lymphomatous) damage to the thoracic duct. Chylous effusion also occurs with the superior vena cava syndrome. Chyliform (cholesterol or pseudochylous) effusionsresemble chylous effusions but are low in triglycerides and high in cholesterol. Chyliform effusions are thought to be due to release of cholesterol from lysed red blood cells and neutrophils in long-standing effusions when absorption is blocked by the thickened pleura. The most common causes are rheumatoid pleuritis and chronic TB. Hemothoraxis bloody fluid (pleural fluid hematocrit>50% peripheral hematocrit) in the pleural space due to trauma or, rarely, as a result of coagulopathy or after rupture of a major blood vessel, such as the aorta or pulmonary artery. Empyemais pus in the pleural space. It can occur as a complication of pneumonia, thoracotomy, abscesses (lung, hepatic, or subdiaphragmatic), or penetrating trauma with secondary infection. Empyema necessitatis is soft-tissue extension of empyema leading to chest wall infection and external drainage. Trapped lungis a lung encased by a fibrous peel caused by empyema or tumor. Because the lung cannot expand, the pleural pressure becomes more negative than normal, increasing transudation of fluid from parietal pleural capillaries. The fluid characteristically is borderline between a transudate and an exudate; ie, the biochemical values are within 15% of the cutoff levels for Light’s criteria (see table). Iatrogenic effusionscan be caused by migration or misplacement of a feeding tube into the trachea or perforation of the superior vena cava by a central venous catheter, leading to infusion of tube feedings or IV solution into the pleural space. are often due to occult Pulmonary Embolism (PE) , 1.Roberts ME, Rahman NM, Maskell NA, et al. British Thoracic Society Guideline for pleural disease.Thorax2023;78(Suppl 3):s1-s42. doi:10.1136/thorax-2022-219784 