A pediatric patient with pneumonia has an infiltrate in the lower half of the right lung. The right heart border is obliterated. In which lobe(s) of the right lung is the infiltrate located?

Question

Quizplus · Accepted Answer

Differences in tissue density allow the viewer to discriminate between different structures. The heart, which is composed of soft tissue of muscle density, is clearly demarcated by a distinct edge from the adjacent air-filled lung. However, if the lung becomes denser from loss of air, as in atelectasis, or if the alveoli become filled with pus, as in pneumonia, the sharp edge between the heart and the lung is no longer apparent. The sign caused when two normal structures lose their distinct edge and blend imperceptibly is widely known as the silhouette sign. If the right heart border is visible next to the infiltrate, the pneumonia is located in the right lower lobe. If the right heart border is obliterated, the infiltrate must be located in the right middle lobe, which resides immediately next to and in the same plane as the right side of the heart. Because the right lower lobe does not lie in the same plane as the right heart border, the two structures remain distinct on a chest radiograph.

A Pediatric Patient with Pneumonia Has an Infiltrate in the Lower