Pleural Effusions

There are normally a few milliliters of fluid in the pleural space; about 75 mL are required to blunt the posterior costophrenic sulcus (seen on the lateral view) and about 200-300 mL to blunt the lateral costophrenic sulcus (seen on the frontal view); approximately 2 liters of fluid will cause opacification of the entire hemithorax in an adult.

Blunting of the Costophrenic Angles

• As the subpulmonic effusion grows in size, it first fills and thus blunts the posterior costophrenic sulcus, visible on the lateral chest. This occurs with approximately 75 cc of fluid.
• When the effusion reaches about 300 mL in size, it blunts the lateral costophrenic angle, visible on the frontal chest radiograph
  
  

Causes of Pleural Effusions

Bilateral Pleural Effusions. There is blunting of both costophrenic angles, right greater than left. The fluid has a characteristic meniscus shape. Bilateral pleural effusions are most frequently the result of congestive heart failure.