Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is increased opacification of the retrocardiac region with obscuration of the left hemidiaphragm , findings which is of uncertain etiology . No clear correlate is seen on the lateral projection , though given the clinical circumstance , atelectasis and early developing pneumonia should be considered . The right lung is clear . There is no pulmonary edema . No pneumothorax is evident . Mediastinal and hilar contours appear within normal limits .
    OUTPUT:
    
Left basilar opacity , possible atelectasis or early pneumonia . Consider follow - up radiographs for further assessment .