- Pulmonary sequestration is an embryonic mass of lung tissue that has no identifiable bronchial communication and that receives its blood supply from one or more anomalous systemic arteries.
- This congenital anomaly can be classified:
- Extralobar sequestration (ELS) or
- Intralobar sequestration (ILS)
- Named extralobar because it lies outside of the normal visceral pleura; it also may lie outside of the thorax in a subdiaphragmatic position in as many as 10% of patients.
- Many patients with ELS present in infancy with respiratory distress and chronic cough
- The arterial supply is predominantly via systemic arteries (95%) rather than pulmonary arteries (5%)
- Systemic arteries are commonly branches of the thoracic aorta or the abdominal aorta (80%).
- In rare cases, the supply may be from anomalous vessels arising from the splenic, gastric, subclavian, and intercostal vessels.
- Venous drainage also occurs most commonly via the systemic veins (75%), for example, the inferior vena cava (IVC) or azygos or portal veins rather than pulmonary veins (25%).
- Intrapulmonary sequestration is usually diagnosed later in childhood or adulthood when the patient presents with infection.
- May contain air via the pores of Kohn or a connection to normal small bronchi.
- The arterial supply is systemic in origin and arrives via the descending thoracic aorta (73%), the abdominal aorta or celiac axis artery (21%), and the intercostal arteries (4%).
- In 95% of patients, venous drainage occurs via the pulmonary veins; in 5% of patients, venous drainage occurs via the IVC, the superior vena cava (SVC), the azygos systems, or the intercostal veins.
 Imaging Findings