encopresis

My 13 year old son has encopresis. We have been dealing with this
since he was very little. We have been to two pediatric
gastroenterologists, 2 psychologists, and a psychiatrist and still have
no cure. He is a smart, happy etroverted boy who simply can't or won't
stay clean. We have just started with an adult gastroenterologist in
hopes that now that he is a young man, he can develop some real desire
to get clean. He had a barium enema last week to determine if there is
any physical deformity and have not gotten the results; however, I
suspect he's fine in that regard. My question: the doctor mentioned
biofeedback as a possible treatment. Does anyone out there know
anything about it and have you had any success with it. And also, does
anyone have any thoughts on other things we might try? Thanks. Ruth