Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Portable AP upright radiograph of the chest was obtained . New opacity seen in the left base is compatible with a pneumonia . Opacification of the right hemithorax is compatible with history of pneumonectomy and resultant rightward shift of mediastinal structures . Cardiac silhouette is not well evaluated . Accompanying left pleural effusion may be present . No pneumothorax is seen .
    OUTPUT:
    
Left basal pneumonia . Followup radiograph four weeks after treatment is recommended .