Bronchiectasis involves permanent dilation of which airways?

• A. Bronchioles and bronchi
• B. Alveoli
• C. Terminal bronchioles
• D. Alveolar ducts

Answer: (A)

Bronchiectasis is defined by irreversible dilation of the conducting airways because of destruction of the elastic and muscular walls from chronic infection and inflammation. This process most clearly affects the larger airways—the bronchi—and can extend into the nearby bronchioles. The alveoli and alveolar ducts aren’t the sites where permanent dilation occurs, since bronchiectasis involves the airway walls, not the air sacs or the distal gas-exchange structures. The dilation of the bronchi and bronchioles best matches the description of bronchiectasis, which is why that choice is the best.