Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: AP upright and lateral views of the chest were provided . Midline sternotomy wires and mediastinal clips are again noted . There is persistent left basilar opacity which likely reflects atelectasis , though pneumonia is difficult to exclude . Right lung remains clear . Small left pleural effusion would be difficult to exclude . The heart size appears within normal limits . The mediastinal contour is normal . Bony structures are intact .
    OUTPUT:
    
Persistent left basal opacity likely reflects atelectasis with possible small left pleural effusion . Overall appearance appears slightly improved from prior exam dated ___ .