Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Portable semi-upright radiograph of the chest demonstrates low lung volumes with resulting bronchovascular crowding . The area of opacification at the left base is stable as compared to the prior study . There is only minimal soft tissue air collection in the left chest wall . The cardiomediastinal and hilar contours are unremarkable . The right lung is normal . There is no pneumothorax .
    OUTPUT:
    
Stable - appearing opacity at the left base .