Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Frontal and lateral chest radiograph demonstrate slightly lower lung volumes from previous examination with bibasilar atelectasis . New triangular - shaped retrocardiac opacity with mild obscuration of the left hemidiaphragm . No additional focal opacity . No pleural effusion or pneumothorax . Heart size , mediastinal contour , and hila are unremarkable . Interval removal of right PICC line . Limited assessment of the osseous structures again demonstrates a vertebral stabilization device . Visualized upper abdomen is unremarkable .
    OUTPUT:
    
New triangular retrocardiac opacity is most consistent atelectasis .