Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is slightly improved aeration at the left lung base with persistent retrocardiac opacification and air bronchograms projecting the left heart border . Opacification at the right lung base is unchanged . No pleural effusion or pneumothorax is seen . The cardiac silhouette is normal in size . The mediastinal and hilar contours are within normal limits . Mild calcification of the aortic knob is again noted .
    OUTPUT:
    
Bilateral lower lobe opacities worrisome for multifocal pneumonia or aspiration pneumonia are not significantly changed from ___ .