Adolescent bowel incontinence

[nsrsgo]

My granddaughter is 12 and about a year ago started having bowel incontinence for no particular reason.  A blood test has ruled out celiac disease and the pediatrician suspects anal sphincter relaxation due to a hx of constipation.  We have done the Miralax once a day, fiber tabs, bathroom visits every 2 hours.  It is not getting better.  She has gas and it comes.  Often she cannot tell it is going to happen.  We are at a loss.