Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The cardiac , mediastinal and hilar contours are unremarkable . Minimal opacification at the left lung base appears most consistent with atelectasis , underlying infection is less likely but can not be excluded in the correct clinical setting . There is no evidence of pleural effusion or pneumothorax .
    OUTPUT:
    
Minimal opacification at the left lung base likely represents atelectasis ; however , infectious process , although less likely , not excluded in the correct clinical setting .