Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Frontal and lateral views of the chest were obtained . Slight left base retrocardiac opacity most likely relates to atelectasis , less likely early infectious process . Right lung is clear . There are low lung volumes . No pleural effusion or pneumothorax is seen . The cardiac silhouette is not enlarged . The aorta is calcified and tortuous . Degenerative changes are seen along the spine , although not well evaluated .
    OUTPUT:
    
Mild left base opacity most likely represents atelectasis , although an early consolidation is not entirely excluded , but felt less likely .