Suggest Treatment For Bowel Incontinence In Child

hi, my 5 yr old son has a h/o ano-rectal pull through surgery since he was born with high imperforate anus. The pull through was done when he was 9 months old. But still he is always soiling his pants as if he has no control on his stool or may be he has no spincter muscles. I am deeply worried of his future, whether he will be able to lead a normal life. Also he is inly 15.5 kgs and I think he is under weight and shortest in his class. Please help. Thanks
-S.V, Mumbai