Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is a subtle ill - defined opacity in the right upper lung which may represent focal aspiration . There is no pleural effusion . No pneumothorax is evident . Cardiomediastinal and hilar contours are within normal limits given the AP technique . No subdiaphragmatic free air is identified . Retained contrast is seen within the transverse colon .
    OUTPUT:
    
Subtle opacity within the right upper lung may be due to focal aspiration . No free air .