Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Single portable view of the chest is compared to previous exam from earlier the same day at 4 : 15 performed at an outside institution . Patchy retrocardiac opacity is seen . Elsewhere , the lungs are clear without evidence of consolidation , large effusion or pulmonary vascular congestion . Cardiomediastinal silhouette is within normal limits . Mitral annular calcifications are noted in addition to atherosclerotic calcifications throughout the aorta . Osseous and soft tissue structures are unremarkable .
    OUTPUT:
    
Patchy retrocardiac opacity , potentially due to aspiration , infection or atelectasis . No evidence of pulmonary vascular congestion .