Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is a small region of patchy density in the left lower lobe in the retrocardiac region . . The cardiomediastinal and hilar contours are within normal limits . There is no effusion or pneumothorax . Again demonstrated is a spinal stimulator , unchanged in position .
    OUTPUT:
    
There is a small region of patchy density in the left lower lobe . There is no pneumothorax or CHF .