Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Frontal and lateral chest radiographs demonstrate a normal cardiomediastinal silhouette and well - aerated lungs . A left retrocardiac opacity partially obscuring the hemidiaphragm on lateral view is also associated with mild volume loss with slight elevation of the left hemidiaphragm . There is also a small left pleural effusion . No pneumothorax is identified . The visualized upper abdomen is unremarkable .
    OUTPUT:
    
Left lower lobe retrocardiac opacity , concerning for infectious pneumonia with likely component of coexisting atelectasis . Small left pleural effusion .