Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The cardiomediastinal silhouette and pulmonary vasculature are unremarkable . The lungs are clear and hyperinflated , consistent with emphysema . A large left perihilar bleb is noted , better assessed on prior CT scan of the chest . There is no pneumothorax or pleural effusion .
    OUTPUT:
    
No acute intrathoracic findings .