Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The tip of the left internal jugular central venous catheter projects over the aortic arch . A dense retrocardiac opacity is present , presumed to reflect atelectasis however underlying pneumonia can not be excluded . Small left pleural effusion . No pneumothorax identified . The size the cardiac silhouette is enlarged . Degenerative changes of the glenohumeral and acromioclavicular joints bilaterally are noted .
    OUTPUT:
    
The tip of the left internal jugular central venous catheter projects over the aortic arch . Dense retrocardiac opacity is presumed to reflect atelectasis and a small pleural effusion . Underlying pneumonia can not however be excluded .