In lobar pneumonia, what is the classic radiographic and exam finding?

• A. Interstitial infiltrates diffusely across both lungs
• B. Cavitation
• C. Consolidation of a single lobe with alveolar exudate and air bronchograms
• D. Pleural effusion only

Answer: (C)

In lobar pneumonia the key idea is that inflammation fills the air spaces of one entire lobe, causing focal consolidation. On a chest X-ray this shows up as a dense, homogeneous opacity confined to a single lobe. The classic radiographic sign is air bronchograms—air-filled bronchi stand out within the opaque, consolidated alveolar tissue because the surrounding alveoli are filled with exudate.

Clinically, this consolidation manifests as exam findings like dullness to percussion and increased tactile fremitus over the affected area, along with bronchial breath sounds and crackles on auscultation. These exam features reflect the loss of air in the alveoli and the dense, solid-like nature of the consolidated tissue.

Other patterns—diffuse interstitial infiltrates, cavitation, or effusion alone—don’t align with the typical single-lobe consolidation seen in classic lobar pneumonia.