Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Heart size is within normal limits . The cardiomediastinal silhouette is unchanged . Atelectasis is noted at the right lung base . An opacity at the left lung base could represent atelectasis , however pneumonia can not be excluded .
    OUTPUT:
    
An opacity at the left lung base could represent atelectasis or focal bacterial pneumonia in the appropriate clinical setting . Standard PA and lateral chest radiographs may be helpful for more complete characterization if warranted clinically .