I'm an expert in this situation. My daughter had her first kidney infection at 3.5 months and we did the VCUG within a couple of weeks. She came back with Stage 3 reflux and was put on antibiotics daily. She had another VCUG at ages 11 months and 26 months then had the Deflux surgery July of '08 to correct, which was successful. Saying that, the easiest of the procedure was the first time when she was so young, couldn't resist and didn't remember a thing; it was by far the least invasive emotionally on all involved.
At the 11 month mark, the reflux had progressed to stage 4 but they allowed her body more time to outgrow it which turned out to be the best thing. At 26 months, it had decreased (with lots of prayers in her honor) to stage 2 which allowed for them to do the Deflux procedure.
Since then, she has had 3 UTI's, not kidney infections, because she would hold her urine when potty training b/c or her experiences. It's been an ongoing battle but we are finally getting out of it after 3.5 year.
Saying all of that, I would not wait for a 3rd UTI to do the procedure. At this age, you will be more affected than she will. They will have to do a catheter, which you may have already experienced with the infections, put dye in her little body then wait for her to void to take pictures. She will not be able to hold that amount of fluid but a couple minutes so she's so young for it to be a pretty quick procedure.
They always told me the fear is to damage the kideys and the more infections, the more of a chance that can happen.
Your life will be different around fevers, etc, from here on out if they find that she has reflux but it's a fixable problem with healthy childhood.
You are welcome to contact me with any questions and I hope everything goes well.
God Bless,
S.