Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Heart size is normal . The aorta is tortuous . Mediastinal and hilar contours otherwise are unremarkable . There is no pulmonary vascular congestion . Minimal patchy retrocardiac opacity is noted . No pleural effusion or pneumothorax is seen . There are no acute osseous abnormalities .
    OUTPUT:
    
Minimal retrocardiac patchy opacity , likely atelectasis .