HI Thank for asking to HCM I really appreciate your concern for your son the reason for vomiting need to be rule out at that time only before removing the gall bladder, central nervous system is the first cause when there is no sing of any infectious disease, like wise other system of body being taken into consideration and investigation done accordingly, both the medical and surgical problem could be there, if this turned unremarkable then it has to be psychological problem, now you have to begin the investigation right from new history and for that talk to his doctor, hope this information helps you, have nice day.