Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Frontal and lateral radiographs of the chest demonstrate an unchanged left chest wall pacemaker with right atrial and ventricular leads . There is a small left pleural effusion , unchanged . Additionally , mild bibasilar atelectasis is present , although there is some increase in focal consolidation at the left base which may be attributable to an infectious process . The opacification in the retrocardiac region may also be a function of atelectasis and developing pneumonia . No pneumothorax is appreciated . The cardiac and mediastinal contours are otherwise within normal limits .
    OUTPUT:
    
Bibasilar atelectasis with increased retrocardiac opacity which may represent left lower lobe pneumonia .