Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Frontal and lateral views of the chest were obtained . Subtle left base retrocardiac opacity , slightly increased as compared to the prior study , could relate to atelectasis , although an underlying small consolidation from infection can not be excluded in the appropriate clinical setting . No pleural effusion or pneumothorax . The cardiac and mediastinal silhouettes are unremarkable .
    OUTPUT:
    
Subtle left base retrocardiac opacity , slightly increased as compared to the prior study , could be due to atelectasis , although in the appropriate clinical setting , a small consolidation from infection is not excluded .