Presentation
Two weeks history of shortness of breath, malaise and fever. Infection?
Patient Data
Age: 51
Gender: Female
From the case:
Right middle lobe pneumonia
Frontal

The right heart border silhouette is indistinct with adjacent consolidation medially at the right base.
Left lung clear.
Heart size normal.
Case Discussion
This case illustrates the silhouette sign of Felson, in this case with respect to the right middle lobe.
The right heart border should have a distinct appearance due to the right atrium abutting aerated right middle lobe. In this case the consolidation in the right middle lobe has resulted in loss of this silhouette.