A 67-year-old man with acute dyspnea and risk factors for VTE undergoes CTPA. The radiologist reports several findings. Which of the following is NOT a recognized sign of acute pulmonary embolism on CT?

Explanation

## Distinguishing PE-Related Findings from Non-PE Pathology on CTPA ### Direct and Indirect Signs of PE **Key Point:** CTPA findings in PE fall into two categories: 1. **Direct signs** — intraluminal thrombus 2. **Indirect signs** — secondary effects of PE (RV strain, infarction, atelectasis) ### Recognized CTPA Findings in Acute PE | Finding | Mechanism | Specificity | |---------|-----------|-------------| | Central/lobar PA thrombus | Direct visualization of clot | Highly specific | | Segmental/subsegmental thrombus | Direct visualization in smaller vessels | Specific | | RV dilatation (RV:LV >0.9) | Acute RV strain from afterload | Indirect, prognostic | | PA dilatation (PA:aorta >1) | Pulmonary hypertension from PE | Indirect | | Hampton's hump + pleural effusion | Pulmonary infarction | Indirect | | Subsegmental atelectasis | Parenchymal collapse from ischemia | Indirect | | Mosaic perfusion | Regional oligemia | Indirect | | Septal thickening | Pulmonary edema from RV failure | Indirect | ### Why Diffuse Ground-Glass Opacification Alone Is NOT PE **High-Yield:** Diffuse ground-glass opacification (GGO) as the **sole finding** on CTPA is NOT characteristic of PE. When present, it indicates: - **Interstitial pneumonia** (viral, atypical, PCP) - **Acute respiratory distress syndrome (ARDS)** - **Diffuse alveolar hemorrhage (DAH)** - **Pulmonary edema** (cardiogenic or non-cardiogenic) - **Aspiration** - **Drug-induced lung injury** **Clinical Pearl:** PE may cause **focal** consolidation (Hampton's hump) or **segmental** perfusion defects, but **diffuse GGO without thrombus or indirect signs** should redirect the clinician to alternative diagnoses. If a patient has diffuse GGO on CTPA, look for: - Intraluminal thrombus (to confirm PE) - RV dilatation (indirect sign) - Mosaic perfusion (indirect sign) **Warning:** A CTPA report stating "diffuse ground-glass opacification" as the primary abnormality, with no thrombus or PE-related secondary signs, is more consistent with interstitial lung disease, infection, or pulmonary edema than PE. ### Clinical Context Matters **Tip:** Always correlate CTPA findings with clinical presentation: - **Acute dyspnea + thrombus + RV strain** = PE - **Acute dyspnea + diffuse GGO + no thrombus** = Consider pneumonia, ARDS, pulmonary edema, DAH [cite:Chest Radiology Fundamentals, Harrison 21e Ch 297]