Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is a subtle opacity in the left lower lung on the frontal view , not clearly seen on the lateral . The remaining lung fields are clear . The cardiomediastinal and hilar contours are unremarkable . There is no pleural effusion or pneumothorax .
    OUTPUT:
    
Subtle opacity in the lower lung field might represent atelectasis or infection or even old rib fracture . Recommend follow - up to resolution .