A 58-year-old woman presents to the emergency department with acute onset dyspnea and right-sided pleuritic chest pain for 6 hours. She had undergone total knee replacement 10 days ago. Vital signs: HR 112/min, BP 128/76 mmHg, RR 24/min, SpO₂ 91% on room air. D-dimer is elevated at 2.8 μg/mL. CT pulmonary angiography (CTPA) is performed. The radiologist reports filling defects within the right lower lobe pulmonary arteries with a central location within the vessel lumen, and a peripheral wedge-shaped area of consolidation in the right lower lobe with the apex pointing toward the hilum. What is the most likely radiological finding on CTPA?

Explanation

## Radiological Diagnosis of Pulmonary Embolism with Infarction ### Clinical Context This patient has classic risk factors for venous thromboembolism (recent orthopedic surgery, immobility) and presents with acute dyspnea and pleuritic chest pain—the cardinal symptom of pulmonary infarction. ### Key CTPA Findings Described **Key Point:** The combination of a **central filling defect in the pulmonary artery** (thrombus) AND a **peripheral wedge-shaped consolidation with apex toward the hilum** (Hampton's hump) is pathognomonic for pulmonary embolism with infarction. ### Radiological Features of PE-Related Infarction | Feature | Description | Significance | |---------|-------------|---------------| | **Filling defect** | Central or eccentric thrombus within pulmonary artery lumen | Direct visualization of embolus | | **Wedge-shaped opacity** | Peripheral consolidation, apex pointing centrally (Hampton's hump) | Hemorrhagic infarction | | **Location** | Usually lower lobes (gravity-dependent) | PE preferentially lodges distally | | **Pleural base** | Consolidation touching pleural surface | Indicates infarction, not just PE | ### Why Infarction Occurs Pulmonary infarction develops in only ~10% of PEs because the lung has dual blood supply (pulmonary + bronchial arteries). Infarction occurs when: 1. Distal PE occludes a segmental or subsegmental artery 2. Bronchial collateral circulation is compromised (e.g., pre-existing cardiopulmonary disease, shock) 3. Venous drainage is impaired **High-Yield:** Pleuritic chest pain + wedge-shaped opacity on imaging = **PE with infarction**, not uncomplicated PE. ### Differential Imaging Features | Diagnosis | CTPA Finding | Distinguishing Feature | |-----------|--------------|------------------------| | **PE with infarction** | Filling defect + wedge opacity | Apex toward hilum; follows vascular distribution | | **Pneumonia** | Consolidation only | No filling defect; may be bilateral; air bronchograms | | **Saddle embolus** | Large thrombus at PA bifurcation | Bilateral PE; severe RV strain; no wedge opacity required | **Clinical Pearl:** Hampton's hump is a classic but **not required** for PE diagnosis. Its presence, however, strongly suggests infarction and indicates a worse prognosis than uncomplicated PE. [cite:Harrison 21e Ch 297]