Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: AP portable upright view of the chest . Midline sternotomy wires noted . Tracheostomy tube projects over the superior mediastinum . Clips project over the chest wall . Retrocardiac streaky opacity with left pleural effusion , small again noted . Right lung appears clear though the right CP angle is excluded . Heart and mediastinal contours are unchanged and normal . Bony structures are grossly intact .
    OUTPUT:
    
Retrocardiac opacity unchanged likely represents atelectasis or scarring , though difficult to exclude a subtle pneumonia . Small left pleural effusion .