Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: PA and lateral views of the chest were obtained . Subtle left basilar opacity corresponds to a subtle opacity on today 's CT , possibly representing atelectasis or a very early pneumonia . Otherwise lungs are clear . No pleural effusion or pneumothorax . Cardiomediastinal silhouette normal . Bony structures are intact . Residual contrast is noted in bowel loops in the upper abdomen .
    OUTPUT:
    
Subtle opacity in the left lung base may represent atelectasis or a very early pneumonia .