Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Portable AP upright view of the chest provided . Midline sternotomy wires and mediastinal clips are again noted . There are lower lung opacities which is potential concern for pneumonia . There is no large effusion or pneumothorax . Mild central hilar congestion is somewhat improved from prior exam . The heart size is top normal . The mediastinal contour is unchanged . No definite signs of pneumothorax . Bony structures appear grossly intact .
    OUTPUT:
    
Lower lung opacities which could represent atelectasis versus pneumonia . Possible mild congestion .