Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: A single AP radiograph of the chest was obtained . As before , the patient is status post midline sternotomy and CABG . Lung volumes are slightly low . There is crowding of the bronchovascular structures , but no pulmonary edema is present . New heterogeneous opacities at the left lung base are some combination of atelectasis , and small effusion , though infection is not excluded . The lungs are otherwise clear . There is no pneumothorax . Left sided rib deformities appear chronic . Left PICC has been removed .
    OUTPUT:
    
Heterogeneous opacities at the left lung base could be atelectasis with a small effusion , though infection can not be excluded . No pulmonary edema .