thanks very much for you advice :) greatly appreciated.
Unfortunately, the cause is often not found. I know this from personal experience, I am not a doc. Much of the care is supportive...if there are breathing issues such as severe shortness of breath, there are things that can be done for him such as BiPAP to help deliver adequate breaths. He should see a pulmonologist who will monitor his condition and prescribe anything he may need to help him breathe.
The surgery that you are referring to is plication where they tack down the affected side to prevent it from moving up into the chest cavity upon inspiration (thus allowing him to take the biggest breath that he can).
I hope that he finds relief soon,keeping you both in my thoughts and prayers
Sunny