What are the two most common congenital abnormalities that lead to tree-in-bud opacities?
Cystic fibrosis and Kartagener's
There are tree-in-bud opacities scattered throughout both lungs. There is no associated bronchiectasis, bronchial wall thickening, consolidation, cavitation, or lymphadenopathy. There is no lower lobe predominance, as the distribution is quite diffuse.