Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: AP portable upright view of the chest . Mild elevation of left hemidiaphragm with gas - filled stomach in the left upper quadrant noted . There is very subtle opacity at the left lung base which could represent crowding of bronchovascular markings though early pneumonia difficult to exclude . Right lung is grossly clear . Aorta is unfolded . Heart size appears normal . Degenerative changes at both shoulders is notable .
    OUTPUT:
    
Subtle opacity in the left lower lung may represent pneumonia in the correct clinical setting .