Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There are low lung volumes . Mild patchy bibasilar opacities , not significantly changed since ___ . Mild pulmonary vascular congestion . There are no large pleural effusions or pneumothorax . The hila and mediastinum are within normal limits . Heart is mildly enlarged . No acute osseous abnormalities .
    OUTPUT:
    
Unchanged bibasilar opacities , most likely representing atelectasis , but pneumonia can not be excluded in the appropriate clinical setting .