Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Heart size is normal . The mediastinal contours are remarkable for a tortuous thoracic aorta . The pulmonary vasculature is normal . Lungs are clear except for a subtle new opacity at the left lung base posteriorly overlying the spine on the lateral radiograph . No pleural effusion or pneumothorax is seen . There are no acute osseous abnormalities . Asymmetrical degenerative changes at the first left costochondral junction appear unchanged .
    OUTPUT:
    
New posterior basilar segment left lower lobe opacity could reflect an early or resolving pneumonia .