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Pulmonary sequestration is a rare congenital malformation where a portion of lung tissue lacks normal connection to the tracheobronchial tree and receives blood supply from systemic rather than pulmonary circulation. It is classified as intralobar (within normal lung tissue) or extralobar (separate from normal lung with its own pleural covering). This condition accounts for approximately 1-6% of all congenital pulmonary malformations.
The sequestered lung tissue develops abnormally during embryogenesis, typically between 6-16 weeks of gestation, resulting in aberrant systemic arterial supply usually from the aorta or its branches. Without normal bronchial connections, the affected tissue cannot participate in gas exchange and may become cystic or infected. Venous drainage occurs through pulmonary veins in intralobar sequestrations or systemic veins in extralobar types.
Diagnosis requires high clinical suspicion as symptoms vary from asymptomatic presentation to recurrent pneumonia, chronic cough, or hemoptysis, particularly in the left lower lobe where most cases occur. CT angiography or MRI can identify the aberrant systemic arterial supply, which is pathognomonic for the condition. Treatment typically involves surgical resection to prevent complications such as infection, bleeding, or malignant transformation, though asymptomatic cases may be managed conservatively with regular monitoring.