Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is a subtle increase in opacity overlying the mid to lower left lung compared to the prior exam . Re demonstrated is mild hilar prominence , with cephalization of the vessels in the upper lungs , which may be secondary to mild congestion . The heart size is normal . The aorta is tortuous . There is no large pleural effusion , or pneumothorax . Multiple compression deformities appear stable compared to prior exam from ___ .
    OUTPUT:
    
Subtle increase in opacity overlying the mid to lower left lung , may be secondary to an infectious process or asymmetric pulmonary edema .