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Bronchopulmonary Sequestration
Introduction
Bronchopulmonary sequestration (BPS) is a solid lung lesion of nonfunctioning pulmonary tissue, a supernumerary lobe of the lung, which lacks connection to the tracheobronchial tree and receives its blood supply from an aberrant systemic feeding artery, originating commonly from the descending aorta. Two forms are recognized: intralobar sequestration (ILS), which is incorporated into normal lung tissue, and extralobar sequestration (ELS), which has its own pleural cover and is completely separated from the normal lung. ELS may also be outside the thoracic cavity.
Disorder
Prevalence and Epidemiology
Bronchopulmonary sequestration is the second most common congenital lung anomaly after congenital cystic adenomatoid malformation (CCAM). ELS accounts for most cases of BPS diagnosed prenatally and 25% to 50% of cases of BPS diagnosed postnatally. This difference in prenatal and postnatal prevalence is thought to be explained by the fact that many instances of ILS could be acquired postnatally. ELS was reported to have 4 : 1 male predominance, but recent series report a similar prevalence in both sexes.
Etiology and Pathophysiology
Bronchopulmonary sequestration frequently occurs in the lower left lung. It is thought to originate from a supernumerary caudally positioned lung bud that migrated caudally during lung development together with the esophagus. Development before or after formation of the pleura leads to ILS or ELS, respectively. ELS can be intrathoracic (usually on the left, comprising up to 50% of all cases); located in the anterior and posterior mediastinum (8% and 6%); or outside the chest cavity, most frequently below the diaphragm (up to 18% of cases). ELS and ILS forms of BPS can coexist. ELS has a systemic arterial blood supply from supradiaphragmatic or infradiaphragmatic vessels, normally originating directly from the aorta. ELS masses usually, but not always, have venous connection to systemic vessels (superior vena cava, azygous vein, and hemiazygous vein), while ILS always drains to pulmonary veins.
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