Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Portable upright AP view of the chest was provided . Lung volumes are low . There are bibasilar mild opacities which could represent atelectasis . The heart appears top normal . No definite sign of pneumonia , though the lower lungs are suboptimally assessed . Mediastinal contour is stable with atherosclerotic calcifications along the aortic knob . Bony structures are intact .
    OUTPUT:
    
Suboptimal assessment of the lower lungs due to low lung volumes with probable atelectasis , less likely pneumonia causing obscuration at this level . Mild cardiomegaly .