Pleural effusion - Causes and Symptoms

Definition

Pleural effusions are excess fluid collected in the pleural cavity. Normally, between the parietal and visceral pleural sheets there is a thin film of pleural fluid, of a composition similar to plasma; its presence is important, because it reduces the rubbing between the lungs and the chest wall during breathing. Pleural effusion is the result of inadequate disposal (exudate) or excessive production of this fluid (exudates).

The transudates accumulate due to an imbalance between the hydrostatic pressure and the oncotic pressure of the plasma in the pleural space. The main cause of the formation of transudative effusions is heart failure, followed by cirrhosis with ascites and hypoalbuminemia (generally caused by a nephrotic syndrome).

Exudates, on the other hand, are formed when the local factors that influence the accumulation of pleural fluid are altered and cause an increase in capillary permeability, with exudation of fluid, proteins, cells and other serum components. The causes are numerous; the most common are pneumonia, neoplasms, pulmonary embolism and tuberculosis. Other causes include infectious or inflammatory processes affecting the lung, sarcoidosis, uremia, rheumatoid arthritis, systemic lupus erythematosus, asbestosis, yellow nail syndrome and any pleural metastatic tumor.

To confirm the presence of a pleural effusion, the evaluation begins with physical examination and chest radiography; thoracentesis and analysis of pleural fluid are often necessary to establish the cause. If the diagnosis is not clear, a lateral decubitus X-ray must be performed (it allows to quantify the liquid present and determine whether it is free or saccate) and a chest CT scan. In some cases, an ultrasound is required to locate and guide the collection of small liquid samples.

Further investigations, useful in specific clinical conditions, include pleural fluid culture and Gram staining to confirm the presence of infections and identify the specific causative organism. Furthermore, the dosage of total proteins (multiple myeloma) and amylase (esophageal rupture, malignant neoplasms and pancreatitis), total and differential cell count (viral infections, parasitic diseases and pulmonary infarction) and cytological examination for exclude any malignant tumor. In specific situations, the macroscopic characteristics (odor, color, etc.) of the liquid can contribute to the diagnosis. A putrid smell and the presence of pus, for example, may indicate an anaerobic infection. A hemothorax, characterized by the presence of blood fluid is found in the case of a pulmonary embolism, a trauma, a malignant neoplasm or a rupture of a main vessel, such as the aorta or the pulmonary artery. A chylothorax, on the other hand, is a spill milky white characterized by a high content of triglycerides, generally caused by a trauma or a neoplasm (usually lymphoma) that involves the thoracic duct. Sometimes, the cause of payment remains unknown, despite the in-depth assessment.

Some pleural effusions are asymptomatic; others cause dyspnea and chest pain. Asymptomatic transudates generally require no treatment. Symptomatic, chronic and recurrent effusions, on the other hand, require thoracentesis, the placement of a thoracic drainage, pleurodesis or pleurectomy.