Which lobe is involved?
Opacified right upper zone with a straight lower border is the right upper lobe.
What is the process causing opacification? Collapse or consolidation?
There is volume loss - the horizontal fissure has been elevated. The predominant process here is collapse.
What is the most likely cause of right upper lobe collapse here?
Bronchiolitis. It is often associated with lobar collapse.
Does this child need a follow up film?
No. Providing symptoms resolve following treatment, no follow up is required.
Increased opacification in the right upper zone. Elevation of the horizontal fissure. Features of right upper lobe collapse. Otherwise, the lungs are clear.