Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The lung volumes are low . There is a subtle opacity in the right lung base . The lungs are otherwise clear . There is no pneumothorax or pleural effusion . The heart size is stable and top normal . The hilar and cardiomediastinal contours are normal . Pulmonary vascularity is normal .
    OUTPUT:
    
Subtle opacity in the right base may represent pulmonary vascular crowding due to low lung volumes . In the right clinical setting , an early pneumonia in this region can not be excluded .