Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Lung volumes are low . There are medial right middle lobe and retrocardiac opacities . Mild pulmonary vascular congestion appears similar to the prior examination . There is no definite pleural effusion . There is no evidence of a pneumothorax . Apparent increase in heart size may be due to patient positioning and low lung volumes . The aortic knob is densely calcified .
    OUTPUT:
    
Right middle lobe and retrocardiac opacities may reflect underlying infection or aspiration .