| Discussion: |
There are three lobes in the right lung: 1) right upper lobe (RUL), (2) right middle lobe (RML), and (3) right lower lobe (RLL).
Posteriorly, the RLL extend as far superiorly as the 6th thoracic vertebral body, and extends inferiorly to the diaphragm. Review of the lateral plain film surprisingly shows the superior extent of the RLL; there is considerable overlap between the more anterosuperiorly located RUL and the RLL.
Right lower zone shadowing is combined with obliteration of the hemidiaphragm (silhouette sign). This needs to be differentiated from a pleural effusion. The right heart border, which is anterior, is usually still clearly seen (silhouette sign again). The oblique fissure lies more horizontally and may become visible, giving a sharp upper margin to the shadowing. If the lobe collapses completely, it may appear as a triangular opacity behind the right heart border. The heart border, being anterior will still be clearly seen.
COMMENTARY BY DR. JUD GURNEY (www.chestx-ray.com)
Heart and mediastinum are displaced to the right (for large effusion would be the opposite). Looks like RML and RLL atelectasis to me. Classically confused with pleural effusion.