Lobar Pneumonia (Bacterial)

Gross: One whole lobe is consolidated with decreased crepitation. The size of the affected lobe is normal. However, the color is dark red. The cut surface may ooze fluid, which may be hemorrhagic or purulent. Airways of the affected lobe may contain pus.

Microscopic: All alveolar spaces of the involved lobe contain neutrophiles (contrast with viral pneumonia in which the alveolar septa contain lymphocytes). The bronchioles also are inflamed and have a neutrophilic infiltrate in their walls and lumina. After complete resolution, the underlying lung architecture is preserved.

Legends:

A94-15: This gross photograph of a cut lung shows consolidation and discoloration of most of the lower lobe (red hepatization).

A90-13: This low power photomicrograph shows many alveolar spaces filled with inflammatory infiltrate.

A90-13: This high power photomicrograph shows the infiltrate to be composed of neutrophiles. Note that the alveolar septa are relatively normal.