Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Portable upright frontal view of the chest . The lung volumes are low which causes crowding of the bronchovascular structures . There is mild interstitial edema but no alveolar edema or focal consolidation . Bilateral lower lobe opacities most likely represent atelectasis . No significant pleural effusion or pneumothorax is seen . There is calcification within the aortic knob . There is slight widening of the mediastinum and the heart size is top normal .
    OUTPUT:
    
Mild interstitial edema . Low lung volumes and bilateral lower lobe opacities that most likely represent atelectasis .