A frontal chest radiograph of a febrile patient shows obscuration of the left cardiac border without obscuration of the left dome of the diaphragm. Applying the silhouette sign, where is the consolidation?
- A Anterior segment of the left upper lobe
- B Left lower lobe, superior segment
- C Lingula of the left upper lobe ✓
- D Left middle lobe equivalent
Correct answer: C. Lingula of the left upper lobe
Explanation
Structures touching on a frontal radiograph lose their borders against each other because there is no intervening aerated lung. The lingula abuts the left heart border, so lingular consolidation silhouettes out the cardiac border while leaving the hemidiaphragm sharp. Left lower lobe disease would silhouette the left dome of the diaphragm instead, and anterior upper lobe segments lie higher and contact neither border cleanly.
Reference: Grainger and Allison Diagnostic Radiology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.