Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Portable frontal chest radiograph shows low lung volumes , which results in crowding of bronchovascular structures . A left retrocardiac opacity is presumably atelectasis , however , pneumonia could be considered in the appropriate clinical setting . There is no pleural effusion or pneumothorax . The heart is normal size and the mediastinal contours are unremarkable . No pulmonary edema .
    OUTPUT:
    
Low lung volumes with a retrocardiac opacity which could reflect atelectasis or pneumonia . If possible , repeat study with improved inspiratory effort is recommended