There are several causes leading to a perfusion defect on a VQ scan with an acute pulmonary embolus being only one of them:
Vascular causes
- acute pulmonary embolus
- previous pulmonary embolus (including fat embolism, thromboembolism, air embolism, tumor)
- vasculitides affecting the pulmonary vessels
- granulomatous disease affecting vessels
- other conditions affecting vessels, e.g.
- intravenous drug use (IVDU)
- radiation therapy
- pneumonectomy
- vascular compression/compromise from
- altered pulmonary circulation
- pulmonary artery hypoplasia
- pulmonary sequestration
- cardiac disease
Airway and lung causes
- asthma
- bronchiectasis
- emphysema
- pneumonia
- lymphangitis carcinomatosis
- pulmonary bullae or pulmonary cyst