In most cases, Kennel Cough is more annoying to the owner than it is to the dog, because the dog hacks and coughs at all hours making it difficult for the owner to sleep or concentrate on anything but the hacking sound.
In some instances, though, it does worsen to the point where it CAN cause
pneumonia, and the fact that he had the cloudiness in his chest x-rays and it doesn't seem to be responding to antibiotics sure looks like a case of Kennel Cough that has gotten much worse.