Which pathological finding is characteristic of the acute phase of pulmonary embolism affecting the lung parenchyma?

Explanation

## Pathological Features of Acute Pulmonary Embolism ### Acute Phase Changes **Key Point:** Pulmonary infarction with hemorrhagic consolidation is the characteristic acute pathological finding when PE causes lung tissue necrosis. ### Mechanism of Infarction 1. **Occlusion of pulmonary artery** — blocks blood supply 2. **Ischemic necrosis** — tissue dies due to lack of oxygen 3. **Hemorrhagic infiltration** — bleeding into necrotic tissue from collateral bronchial circulation 4. **Result** — wedge-shaped, hemorrhagic consolidation (usually peripheral, subpleural) ### Gross Appearance - Wedge-shaped or cone-shaped area - Dark red/purple (hemorrhagic) - Firm and elevated above pleural surface - Typically at lung periphery - Often multiple lesions ### Microscopic Features - Coagulative necrosis of alveolar walls - Red blood cells filling alveolar spaces - Fibrin deposition - Minimal inflammatory response in acute phase **High-Yield:** Not all PE causes infarction — only ~10% of PE result in pulmonary infarction because the lung has dual blood supply (pulmonary + bronchial arteries). Infarction occurs when: - Large embolus occludes major pulmonary artery - Underlying cardiopulmonary disease (heart failure, pneumonia) compromises collateral flow **Clinical Pearl:** Hemoptysis and pleuritic chest pain suggest pulmonary infarction; pure PE without infarction may present with dyspnea and tachycardia alone. | Feature | Acute PE (No Infarction) | PE with Infarction | | --- | --- | --- | | Gross finding | Pulmonary artery thrombus only | Wedge hemorrhagic consolidation | | Symptoms | Dyspnea, chest pain, syncope | + Hemoptysis, pleurisy | | Frequency | 90% of PE | 10% of PE |