Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Lung volumes are slightly low , resulting in bronchovascular crowding . Blunting of the left costophrenic angle is most consistent with a small left pleural effusion . There is increased opacity in the retrocardiac region . The heart is mildly enlarged . The aorta is tortuous . No pneumothorax .
    OUTPUT:
    
Small left pleural effusion and retrocardiac opacity , which likely represents atelectasis , however pneumonia could be considered in the appropriate clinical setting .