Pleural fluid should fall with gravity and be in the most dependent part of the hemithorax, based upon patient positioning for the x-ray i.e.Conventional radiography is usually the first step in the detection of a pleural effusion.Pleural effusions can also form when there is transport of peritoneal fluid from the abdominal cavity through the diaphragm or via lymphatics from a subdiaphragmatic process.Decreased pressure in the pleural space, as in atelectasis of the lung due to bronchial obstruction.Lymphangitic blockade by tumor or increased venous pressure that decreases the rate of fluid transport via the thoracic duct.Increasing capillary permeability, as can occur in toxic disruption of the capillary membrane in pneumonia or hypersensitivity reactions.Decreasing colloid osmotic pressure, as in hypoproteinemia.Increasing hydrostatic pressure, as in left heart failure.Etiology of Pleural Effusionįluid accumulates in the pleural space when there is an imbalance in fluid production or resorption. Fluid is produced at the parietal pleura from a capillary bed and is resorbed both at the visceral pleura and by lymphatic drainage throughout the parietal pleura.

Normally, several hundred milliliters of pleural fluid are produced and reabsorbed each day. The margins of the fluid will create a meniscus with the pleura that is not seen with isolated lung consolidation. Pleural fluid occupies space and causes the underlying lung to collapse as there is limited space in the hemithorax.

Pleural fluid may be transudate, exudate, blood, chyle, or infusate. Large Bilateral Pleural Effusions – X-ray and Ultrasound The size of the cardiac silhouette could not be determined due to the pleural fluid. There were large pleural effusions present. Figure 9.14 Chest X-ray displaying large bilateral pleural effusions.