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?

## 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]