Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Frontal and lateral views of the chest demonstrate confluent left lung base opacity obscuring left hemidiaphragm and left cardiac border . Small bilateral pleural effusions . There is no pulmonary edema . Hilar and mediastinal silhouettes are unchanged . Aorta remains tortuous with intra-aortic stent placement . Heart size difficult to assess due to adjacent opacities . There is no pneumothorax . Partially imaged upper abdomen is unremarkable .
    OUTPUT:
    
Left lung base opacity is new since ___ exam , and may represent atelectasis , effusion or infection in the appropriate clinical setting .