Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The cardiac and mediastinal contours are normal , and mild aortic calcifications are again seen . No pleural effusion or pulmonary edema is seen . There is a left basal opacity which may represent supervening infection or chronic lung disease .
    OUTPUT:
    
Opacification of left lung base may represent supervening infection but likely chronic lung disease .