Fecal incontinence

I am hoping to find a reason for my daughter's fecal/urinary incontinence.  She wets/soils herself several times in a day, and through the night.  She has had several medical tests to rule out a physical cause, including a spinal MRI.  I know mentally she is capable of using the toilet, and as her mom, I feel there is cause, possibly dietary, that we can manage if only we could find it.  She has days without a single accident, and then days when she has no control over her bowels and/or bladder.  She's not constipated, and doesn't have diarrhea.  My first attempt at finding a dietary link is to cut out dairy.  Any suggestions at all would be greatly appreciated.
Thanks!

[CalGal]

If deleting dairy doesn't help, you migh want to consider having her do a gluten-free trial. That would mean staying away from anything with wheat, rye, barley or oats in it. It can be difficult in the beginning, but worthwhile if it works for her.

[twinsmomplus2more]

Are you positive that she is not constipated?  Could she be soiling because she has overflow stool due to constipation?  This could also explain the problems with urinary incontinence.  If the bowel is very full, it could be pressing on the bladder.
This is all from experience.  My daughter has had urinary and fecal incontinance all her life.  I took her to many, many specialists for many, many years, and was only recently given the answer.  She has severe neurologic colonic dysfunction.  About half of her colon does not function at all neurologically.  She has no control at all and never did.  We needed to see a motility specialist for a certain test to find the problem.  I'm not saying that this is your daughter's issue, just that it sounds a lot like my daughter's.  Good luck to you both.  I hope you find answers soon:)