Did your g-sons pediatric DR. check for PYLORIC STENOSIS?? Its a rare occurance-most that have it are (first born males). Not always tho!! Its a muscle at the top of the stomach-that opens to let food pass in. If the muscle becomes too thick -it closes off-and the foods shoots back up. My first g-son had this-had simple surgery-then his baby brother had it as well. But they caught it as an infant. But if he's always done it-I'd probably change pediatric Dr.!! He should have found something by age 11!! But do a food intake diary for at least 2 weeks and see if it happens -and check to see if there are any food duplicates!! You didn't say if he was growing normally or not--if it was causing him any weight gain issues!!!! Giood luck and May GOD bless you all.