Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Posterior left base opacity is seen which may be due to infection or aspiration , underlying contusion is not entirely excluded . There is minimal blunting of the posterior costophrenic angles which may be due to relative flattening of the diaphragms , although trace pleural effusions are not excluded . There are relatively low lung volumes . No pneumothorax is seen . Costochondral calcifications are noted . The cardiac silhouette remains top normal to mildly enlarged . The aorta is calcified and tortuous . No displaced fracture is seen .
    OUTPUT:
    
Posterior basilar opacity , best seen on the lateral view could be due to infection or aspiration , underlying contusion not excluded . Minimal blunting of the posterior costophrenic angles , trace pleural effusion not excluded .