Pleural Effusion

Fluid accumulates in the pleural space.

Irrespective of the nature of fluid, radiologically they will look similar. 

Radiological criteria are:
  • Density
  • In dependent portion
    • Costophrenic angle in PA view
    • Anterior and posterior portions of gutter in lateral view
    • Along sides in lateral decubitus position
    • Along posteriorly in supine position, giving diffuse haziness on the side of effusion
  • Silhouette of upper limit of density
    • Upper margin high in axilla in PA view
    • Upper margin high interiorly and posteriorly in lateral view
  • Blunting of costophrenic angle 
  • Lack of identifiable diaphragm  (silhouette sign principle).


  • Massive
  • Unilateral VS bilateral
  • Sub pulmonic
  • Loculated
  • Supine position
  • Lateral decubitus position