Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Portable AP upright chest radiograph is obtained . The heart is mildly enlarged and the aorta is unfolded though overall appearance is unchanged . There are no overt signs of pulmonary edema . There is mild retrocardiac opacity which could represent left lower lobe atelectasis though given underpenetrated technique , evaluation is limited . There is no large effusion or pneumothorax . Clips are noted in the right neck , again similar to prior exam . Bony structures are intact .
    OUTPUT:
    
Mild cardiomegaly with possible left lower lobe atelectasis . No overt signs of pneumonia or edema .