Extralobar pulmonary sequestration (ELS) is a subtype of pulmonary sequestration, the other type being intralobar pulmonary sequestration (ILS).
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Epidemiology
It is usually encountered in infants, most being diagnosed before six months. It is more common in males (M:F 4:1).
Pathology
Extralobar pulmonary sequestration is the less common type of pulmonary sequestration, accounting only for 15-25%.
It is covered by its own pleura and this is what differentiates it from intralobar pulmonary sequestration.
Extralobar pulmonary sequestration receives vascular supply mainly from the aorta (thoracic or abdominal) or from other arterial vessels (splenic, subclavian, gastric, intercostal or multiple vessels) and venous drainage can be either systemic or pulmonary.
Location
There is strong predilection towards the left lower lobe (65-90%).
Associations
Radiographic features
CT
well marginated mass
usually homogeneous, often without internal gas
may contain cystic areas
systemic arterial supply 4
Treatment and prognosis
Surgical excision is the mainstay of treatment.
Differential diagnosis
intralobar pulmonary sequestration: may not be able to differentiate from extralobar pulmonary sequestration on imaging
Furthermore, in an infra-diaphragmatic location, consider 6: