Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Lung volumes are relatively low . There is streaky retrocardiac opacity on the frontal and lateral views . Elsewhere , lungs are clear . Cardiomediastinal silhouette is within normal limits . No acute osseous abnormalities . There is no free intraperitoneal air .
    OUTPUT:
    
Retrocardiac opacity which could be due to atelectasis in the setting of relatively low lung volumes noting that infection could be considered in the proper clinical setting . Repeat with improved inspiratory effort could be performed for clarification if desired .