Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: PA and lateral views of the chest provided . Midline sternotomy wires and mediastinal clips are again noted . Since the prior exam there is improved aeration at the lower lungs . There is only mild residual basilar atelectasis on the left . There is a retrocardiac gas filled structure which corresponds with known hiatal hernia . Cardiomediastinal silhouette appears normal . Bony structures are intact .
    OUTPUT:
    
Mild left basal atelectasis . Hiatal hernia . Otherwise unremarkable .