Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Lung volumes are low . The patient has had prior median sternotomy . Sternotomy wires are intact and aligned . An ill - defined opacity at the left lung base may be due to infection or atelectasis . The heart and mediastinum are within normal limits despite the projection . There is generalized osteopenia . No displaced rib fracture is identified . Metallic right upper quadrant clips denote prior cholecystectomy .
    OUTPUT:
    
Ill - defined opacity at the left lung base may be due to infection or atelectasis . No evidence of displaced rib fracture . An upright PA radiograph or dedicated rib series would provide more sensitive evaluation for rib fracture .