On the upright PA chest x-ray, there is a subtle retrocardiac mass, which is better identified on the lateral view. A follow-up contrast-enhanced computed tomography (CT) demonstrates a soft tissue mass within the posteromedial costophrenic sulcus. Inspection of the axial CT image suggests the presence of a vessel within the anterior aspect of the mass. On the maximum intensity projection multiplanar reconstruction, a vessel clearly arises from the celiac axis to feed the mass. Careful evaluation of the axial CT demonstrates a similar but smaller mass like density within the right posteromedial costophrenic sulcus.
Bronchopulmonary sequestration is defined as nonfunctioning bronchopulmonary tissue, which is isolated from the bronchial tree and receives its arterial supply from the systemic circulation. Sequestrations are divided into intralobar sequestration (75%) and extralobar sequestration (25%). An intralobar sequestration shares the visceral pleura of the adjacent normal lung tissue, has a large aberrant systemic arterial supply, drains via the pulmonary veins, is often identified in older patients, and is typically not associated with other abnormalities. Extralobar sequestration, however, has an independent visceral pleura, a small aberrant systemic arterial supply, drains via the systemic circulation (typically the azygous or hemiazgous vein), presents in childhood, and is often associated with other abnormalities, including congenital diaphragmatic hernia, additional congenital lung abnormalities, or complex heart disease.
On CT, the sequestration appears as a complex mass comprised of solid, fluid, and/or cystic components. The solid component will often demonstrate heterogeneous enhancement. Adjacent to the sequestration, the normal lung may appear hyperinflated or emphysematous. However, identification of the systemic arterial supply, while not necessary for diagnosis, is diagnostic and may require a CT angiogram. When noninvasive imaging is unsuccessful in determining the arterial supply and venous drainage, conventional angiography may be considered.
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