Costophrenic angle

In anatomy, the costophrenic angles are the places where the diaphragms (-phrenic) meet the ribs (costo-).

Each costophrenic angle can normally be seen as on chest X-ray as a sharply-pointed, downward indentation (dark) between each hemi-diaphragm (white) and the adjacent chest wall (white). A small portion of each lung normally reaches into the costophrenic angle. The normal angle usually measures thirty degrees.

With pleural effusion, fluid often builds up in the costophrenic angle (due to gravity). This can push the lung upwards, resulting in "blunting" of costophrenic angle.