Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Lung volumes are low with bronchovascular crowding . Retrocardiac opacity with silhouetting of the left hemidiaphragm and left costophrenic angle may reflect atelectasis and / or infection in the appropriate clinical situation . A left pleural effusion is small . Right lung is clear except for minor atelectasis at the base . Aortic knob calcifications are moderate . No pneumothorax .
    OUTPUT:
    
Limited exam . Low lung volumes . Left lower lobe opacity likely reflects atelectasis and effusion ; however concurrent pneumonia can not be excluded in the appropriate clinical setting .