Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: A right internal jugular hemodialysis port ends at the atriocaval junction . There is a left retrocardiac opacity and a left pleural effusion . The right lung is clear . There is no pneumothorax . The size of the cardiac silhouette can not be determined due to the left pleural effusion . A small amount of subdiaphragmatic free air is noted and expected post-operatively .
    OUTPUT:
    
1 . Left basilar opacity is likely atelectasis , although pneumonia can not be excluded . 2 . Small left pleural effusion . 3 . Post-operative subdiaphragmatic free air .