Gall Bladder Trouble in Teen Girls

Gall bladder disease, come to find out, runs rampant in my family. We don't have stones, just a diseased gall bladder that won't "perform". Mom was finally diagnosed after 15 years of hell (no stones, to many docs, meant no GB problem). After her surgery, the doc told me to expect the same to happen to me. I took it with a grain of salt (ie: didn't really believe him).

Last fall, I had an attack, researched my symptoms on the web and came up with two possible culprits: heart attack and gall bladder. I remembered what the surgeon said and asked mom about her troubles. She told me to get a HIDA scan, which would show a diseased GB in the absence of stones. Bingo.

My daughter, now 17, has been having tummy trouble for 7 or 8 years and you know how kids can be....can't tell you where the pain is, what it feels like, etc. We tried lots of things and finally chalked it up to stress and poor "kid" hygiene. After my surgery, and with the knowledge that this is hereditary, I looked into the possibilty that my daughter could have the same issue.

We went to a GP, who referred her to a gastroenterologist. We have spent the summer doing a battery of tests for (it seems) every disease known to man, culminating with the HIDA scan (even though everyone says she's too young for this).

My question is this:
My "score" on the HIDA scan was 21. My surgeon told me that 80 is normal, 60 is bad, 40 is an indication for surgery but he's more conservative and waits until 35.
My daughter's "score" was 32. Her surgeon, however, tells me that this is on the "lowside of normal". He's agreed to the surgery (as well as removing the appendix at the same time), but the conflicting standards has me questioning my gut instinct to subject my child to this surgery....no matter how routine or low-risk.
Any thoughts? Why the disparity among opinions? (One doc, mine, at Ft. Belvoir Army Hospital; the other, daughter's, at Walter Reed Army Medical Center---if it matters)

Thank you.

I'm fairly certain, based on what I've learned of my family history and the symptoms that accompany biliary diskenesia that the diagnosis is correct. 

It bothers me, though, that there is such a disparity in what two different surgeons count as normal.

Bottom line, I want to do what's best for my child.