Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: PA and lateral views of the chest demonstrate post - surgical changes related to prior left thoracotomy and left upper lobectomy . There is elevation of the left hemidiaphragm , as before . A new retrocardiac opacity in the posterior left lower lobe may be related to prior surgery , although infection can not be excluded . The right lung is grossly clear , with persistent hyperinflation and slight leftward shift of the mediastinal structures . The heart is normal in size . An air - filled cavity within the left apex contains some fluid , similar in appearance to the prior study from ___ . Scarring in the right lung apex is unchanged .
    OUTPUT:
    
Stable post-operative changes related to prior left thoracotomy and left upper lung pneumonectomy . Subsequently obtained chest CT shows no evidence of pneumonia .