Wedge-Shaped Pleural-Based Defect: Pulmonary Embolism
CC BY 3.0 · Myohan / Wikimedia Commons · source file
Question
On a lung perfusion scan, a wedge-shaped, PLEURAL-BASED perfusion defect (broad base at the pleural surface, apex pointing toward the hilum) is identified. The ventilation scan is normal in the same region. This WEDGE-SHAPED peripheral mismatch is the classic scintigraphic appearance of:
- APleural effusion
- BPulmonary contusion
- CPneumonia with consolidation
- DPulmonary embolism — embolic occlusion of a segmental or subsegmental pulmonary artery
Show the answer and explanation
D. Pulmonary embolism — embolic occlusion of a segmental or subsegmental pulmonary artery
The classic scintigraphic appearance of PE on perfusion scan is a WEDGE-SHAPED (or 'pleural-based') perfusion defect, where the broad base is at the pleural surface and the narrow apex points toward the hilum — following the anatomic distribution of a pulmonary artery branch. This shape reflects the vascular anatomy of a segmental or subsegmental artery territory. The corresponding ventilation scan is NORMAL (ventilation-perfusion mismatch). Multiple such wedge-shaped defects in different lung zones constitute a high probability pattern. Pleural effusion causes a uniformly decreased peripheral perfusion without a discrete wedge shape.
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