Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Heart size is normal , with a mildly tortuous aorta . Hilar contours are normal . Retrocardiac densities are slightly increased on today 's examination with correlative increasing opacity in the posterior left lower lung on lateral view , worrisome for infection . There is a band of linear atelectasis in the right lung base . The lung apices are clear . There is no pleural effusion or pneumothorax .
    OUTPUT:
    
Increasing retrocardiac opacity concerning for left lower lobe pneumonia . Results were discussed over the telephone with Dr . ___ by ___ ___ at 10 :41 a .m . on ___ at the time of initial review .