A 52-year-old woman with acute dyspnea and pleuritic chest pain undergoes CT pulmonary angiography (CTPA). The scan shows a wedge-shaped, peripheral opacity with the apex pointing toward the hilum. Which of the following findings is NOT typically associated with acute pulmonary embolism on CTPA?

Question

Accepted Answer

B. Mediastinal lymphadenopathy as the primary finding. ## CT Imaging Findings in Pulmonary Embolism

### Classic CTPA Signs of PE

**Key Point:** The hallmark direct sign of PE is the **intraluminal thrombus** within a pulmonary artery — a low-attenuation filling defect surrounded by contrast in the arterial phase.

**High-Yield:** Common CTPA findings in acute PE include:

| Finding | Significance | Frequency |
|---------|--------------|----------|
| Intraluminal thrombus | Direct sign of PE | Most specific |
| PA dilatation (PA:aorta >1) | Right heart strain | Common in massive PE |
| Hampton's hump | Wedge infarct (peripheral, pleural-based) | ~10% of PE cases |
| Mosaic perfusion | Areas of reduced perfusion (oligemia) | Indirect sign, common |
| Right ventricular dilatation | RV strain from acute afterload | Prognostic significance |
| Septal thickening | Pulmonary edema from RV failure | Late finding |

### Why Mediastinal Lymphadenopathy Is NOT a PE Finding

**Clinical Pearl:** Mediastinal lymphadenopathy (>10 mm short axis) is NOT a feature of acute PE. When present, it should prompt investigation for alternative diagnoses:
  - Lymphoma
  - Lung malignancy
  - Sarcoidosis
  - Tuberculosis
  - Metastatic disease

**Warning:** A patient with CTPA showing mediastinal lymphadenopathy as the **primary finding** likely has a different diagnosis. PE may coexist, but the lymphadenopathy is incidental or points to another pathology.

**Tip:** In exam questions, if a CTPA finding is described as "primary" or "main," mediastinal lymphadenopathy should raise suspicion that PE is NOT the correct diagnosis.

### Infarction vs. Non-Infarction PE

- **Hampton's hump** occurs when PE causes **pulmonary infarction** (wedge-shaped opacity, pleural-based, apex toward hilum) — seen in ~10% of PE cases
- **Mosaic perfusion** reflects areas of **reduced blood flow** without infarction — more common than Hampton's hump
- **Direct thrombus sign** is the gold standard but may be subtle in small peripheral emboli

[cite:Chest Radiology Fundamentals, Felson's Principles of Chest Roentgenology]

Answer

A. Hampton's hump (wedge-shaped peripheral consolidation)

Answer

C. Pulmonary artery dilatation with PA:aorta ratio >1

Answer

D. Mosaic perfusion pattern in non-infarcted lung

A 52-year-old woman with acute dyspnea and pleuritic chest pain undergoes CT pulmonary angiography (CTPA). The scan shows a wedge-shaped, peripheral opacity with the apex pointing toward the hilum. Which of the following findings is NOT typically associated with acute pulmonary embolism on CTPA?

Explanation

CT Imaging Findings in Pulmonary Embolism

Classic CTPA Signs of PE

Why Mediastinal Lymphadenopathy Is NOT a PE Finding

Infarction vs. Non-Infarction PE

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Finding	Significance	Frequency
Intraluminal thrombus	Direct sign of PE	Most specific
PA dilatation (PA:aorta >1)	Right heart strain	Common in massive PE
Hampton's hump	Wedge infarct (peripheral, pleural-based)	~10% of PE cases
Mosaic perfusion	Areas of reduced perfusion (oligemia)	Indirect sign, common
Right ventricular dilatation	RV strain from acute afterload	Prognostic significance
Septal thickening	Pulmonary edema from RV failure	Late finding