A 68-year-old man with COPD presents with acute lobar pneumonia confirmed by Streptococcus pneumoniae on blood culture. He deteriorates despite appropriate antibiotics and dies. At post-mortem, the right lower lobe shows the appearance marked **A** in the diagram—a uniformly consolidated, firm, airless, red-brown lobe with a dry, granular, liver-like cut surface, sharply demarcated at the fissure from adjacent lobes. Which of the following best describes the pathological stage represented by this gross appearance?

Question

Accepted Answer

B. Red hepatisation—alveolar consolidation with fibrin, neutrophils, and intact alveolar architecture. ## Why Red hepatisation is right

The structure marked **A**—a uniformly consolidated, firm, red-brown lobe with a dry, granular, liver-like cut surface and intact alveolar architecture—is the pathognomonic gross appearance of the red hepatisation stage of lobar pneumonia. This stage occurs 2–3 days after onset and is characterized histologically by alveolar filling with fibrin, red blood cells, neutrophils, and bacteria, while the underlying lung architecture remains intact. The red-brown colour reflects the congestion and RBC extravasation; the liver-like consistency reflects the consolidation and loss of air. This is the classic appearance in fatal pneumococcal pneumonia, as described in Robbins and Cotran (10th ed., Ch. The Lung).

## Why each distractor is wrong

- **Grey hepatisation**: Occurs in the later stage (days 4–8), when fibrinolysis begins and neutrophils predominate over RBCs, giving a grey-white appearance. The clinical scenario describes death on day 4, but the gross appearance is distinctly red-brown, not grey.
- **Resolution**: Represents the final stage (days 8–14+), characterized by resorption of exudate and restoration of normal architecture. The described lobe is still consolidated and firm, not resolving.
- **Suppuration**: Represents abscess formation with liquefactive necrosis and loss of normal alveolar architecture. The post-mortem description explicitly notes "intact architecture" and a "granular cut surface," not liquefaction or abscess.

**High-Yield:** Red hepatisation = red-brown, firm, liver-like consolidation with intact architecture (days 2–3); grey hepatisation = grey-white, softer appearance with fibrinolysis (days 4–8).

[cite: Robbins and Cotran Pathologic Basis of Disease, 10th ed., Ch. The Lung.]

Answer

A. Suppuration—abscess formation with liquefactive necrosis and loss of normal architecture

Answer

C. Resolution—resorption of exudate with restoration of normal lung architecture

Answer

D. Grey hepatisation—alveolar consolidation with fibrin, neutrophils, and early fibrinolysis

Explanation

Why Red hepatisation is right

Why each distractor is wrong

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