Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Right lung volume is slightly lower than left , similar to prior exam . There is no evidence of pulmonary edema . Opacity in the left lung base likely represents atelectasis , although can not completely exclude aspiration or pneumonia in the right clinical setting . Platelike atelectasis in the left mid lung is similar prior exam . There is no pleural effusion or pneumothorax . The cardiomediastinal silhouette is enlarged and the aorta is tortuous , similar to prior exam . Orthopedic hardware is noted in the left humerus .
    OUTPUT:
    
No evidence of pulmonary edema . Opacity in the left lung base , likely reflecting atelectasis but can not completely exclude aspiration or pneumonia in the proper clinical setting .