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?

Question

Accepted Answer

A. Acute pulmonary embolism with infarction. ## 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]

![Pulmonary Embolism — CT Imaging diagram](https://mmcphlazjonnzmdysowq.supabase.co/storage/v1/object/public/blog-images/explanation/3948.webp)

Answer

B. Acute aortic dissection extending into pulmonary arteries

Answer

C. Pneumonia with septic emboli

Answer

D. Saddle embolus at the pulmonary artery bifurcation with acute right heart strain

Explanation

Radiological Diagnosis of Pulmonary Embolism with Infarction

Clinical Context

Key CTPA Findings Described

Radiological Features of PE-Related Infarction

Why Infarction Occurs

Differential Imaging Features

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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

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