SUBPULMONIC EFFUSION

 The first place for pleural fluid to accumulate in an erect patient is the space between the inferior surface of the lower lobe and the diaphragm. Only after filling this space, it will spill over into the costophrenic angles.

In CXR, the subpulmonic effusion stimulates diaphragmatic elevation thus called as pseudo diaphragmatic contour.

1. PA view :-The peak of pseudo diaphragmatic configuration is lateral to that normal hemidiaphragm being situated near the junction of middle and lateral third of diaphragm.

2.PA view :-On the left side, subpulmonic effusion is suspected if the distance between the gastric air bubble shadow and pseudo diaphragmatic shadow is more than 2cm.

3.Lateral view ;-upper margin of fluid meets the major fissure.

4.PA view: thin triangular opacity in the left paramediastinal zone with apex half way upto the mediastinum and its base continuous with pseudo diaphragmatic shadow.

5.PA view : The pulmonary vessels normally visible below the diaphragmatic contour, cannot be seen through the pseudo diaphragmatic contour of the subpulmonic effusion. 

Ref : Fraser