This almost certainly sounds like a typical gall
bladder attack. He could have
gall stones, and they may cause irritation within the
gall bladder. This causes pain in the upper right side, under ribcage, can migrate into back, accompanied with nausea, headaches, and even fever at times. The pain can even ache in the right shoulder and down the arm.
Lemon juice with a couple tsps of olive oil is a great home remedy for this. It has always worked for me.