Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Airspace opacities in the superior subsegment of the left lower lobe are unchanged from the immediate prior study consistent with an acute pneumonia . Additional nonspecific opacity at the left lung base has improved and may have reflected a focus of atelectasis given rapid improvement . There is no pleural effusion , pneumothorax , or pulmonary edema . The cardiomediastinal silhouette is stable .
    OUTPUT:
    
Short interval stability of a superior subsegment left lower lobe pneumonia .