Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The cardiomediastinal silhouette and pulmonary vasculature are unremarkable . There are small , bilateral pleural effusions . In the retrocardiac region , there is a streaky opacity . While this may represent atelectasis , aspiration or pneumonia is not entirely excluded .
    OUTPUT:
    
Left lower lobe retrocardiac opacity may represent atelectasis , aspiration , or developing infectious pneumonia in the appropriate clinical context . Follow - up chest x-ray ___ weeks after treatment is recommended to document resolution .