Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Right lung is clear . Small retrocardiac opacity is noted . Trace left pleural effusion has decreased since prior examination . No right pleural effusion . Heart is top - normal in size . Mediastinal contour and hila are unremarkable with prominence of the right paratracheal stripe which is unchanged since ___ . Intact median sternotomy wires are noted .
    OUTPUT:
    
1 . Left lower lobe atelectasis rather than pneumonia . 2 . Trace residual left pleural effusion has significantly decreased since prior examination .