Pulmonary Sequestration

Pulmonary sequestration is a congenital mass of dysplastic, non-functioning lung tissue. It has no normal connection to the tracheobronchial tree and receives blood from the systemic circulation—usually the descending thoracic aorta—rather than from the pulmonary arteries. It is thought to develop from an accessory lung bud arising from the primitive foregut. The abnormal tissue is not simply “extra lung.” Because it lacks normal airway drainage and mucociliary clearance, retained secretions and infection can recur. Because its arterial inflow is systemic, the feeding vessel is under substantially higher pressure than a normal pulmonary artery. Both features explain the two classic later presentations: repeated focal pneumonia and haemoptysis. The anatomic type predicts the physiology and the likely operation: - Intralobar sequestration (ILS) is enclosed within the visceral pleura of an adjacent normal lobe. It accounts for roughly 75% to 86% of cases and usually drains through the pulmonary veins. Most are in the left lower lobe, especially the posterior basal segment. - Extralobar sequestration (ELS) has its own pleural envelope and usually drains into systemic veins such as the azygos, hemiazygos, or...