Teen Bedwetting

My grandson is 15 yrs old and still wets the bed.  My daughter has taken him to their regular family dr. and he says he will grow out of it.  My daughter was also a bedwetter and we took her to a kidney specialists who ran tests and then decided she had a small bladder and slept what is called death sleep (really deep sleep that does not awaken by just calling..has to be shook several times to get awake).  This bedwetting is an embarassment to him and he cannot go to any thing at school that has to be overnight.  His 6th grade class trip to Washington DC we paid extra for a room so I could go and stay in that room with him since he wears a pull up at night.  Is there anything than can be done to help him with this?  He can go to be at 12:00 a.m. and by 1:30 he has usually already wet the bed. Even though he goes to the bathroom before he goes to bed.