Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is retrocardiac and left basilar opacity silhouetting the hemidiaphragm . The lungs are otherwise clear . The cardiomediastinal silhouette is within normal limits . Right - sided PICC seen with tip in the mid SVC . Catheter also projects over the left upper quadrant . No acute osseous abnormality is identified .
    OUTPUT:
    
Left basilar opacity likely due to an effusion with underlying atelectasis , although infection is possible .