Which statement best defines extralobar sequestration?

• A. A congenital defect in which a part of a lung does not connect to the airway and is anatomically separate from the rest of the lung, inhabiting its own pleural sac.
• B. A normal portion of lung that connects to the airway.
• C. Sequestration within the same pleural sac as the rest of the lung.
• D. A lobar collapse due to airway obstruction.

Answer: (A)

Extralobar sequestration describes a congenital piece of nonfunctioning lung tissue that is completely separate from the normal lung, housed in its own pleural sac, and does not connect to the tracheobronchial tree. This distinct pleural covering is the defining feature that sets extralobar sequestration apart from other lung anomalies. The sequestered tissue typically receives blood from the systemic circulation, often directly from the aorta, rather than from the pulmonary arteries.

This makes the statement the best choice because it specifically notes the tissue is anatomically separate and has its own pleural sac, which is the hallmark of extralobar sequestration. If the tissue were described as sharing the same pleura with the normal lung, that would fit intralobar sequestration. If it described normal lung tissue that connects to the airway, that would not be sequestration at all. And a description of lobar collapse due to airway obstruction describes a different process entirely.