P.,
Both of my girls have needed to have an upper GI, my youngest has actually had several.
Each hospital may perform it slightly different, but I found it much less invasive than other tests that have been performed on my youngest (who was born extremely prematurely and has had tons of problems to overcome).
At the children's hospital where my daughters had their upper GI's performed they had a special little backboard that they strapped her into. It was well cushioned and kept her arms positioned above her head and the softly padded velcro straps held her still while the test was performed. A technician took my oldest child to the other side of the glass wall, and a second technician and I were dressed in lead vests and stayed with my youngest while the test was performed. A Dr. read the scans as the technician and I had her drink barium and rotated her in different positions so the Dr. could get the exact pictures he needed. Overall it was much easier than I had anticipated. With adults an upper GI often consists of having to be scoped and I was concerned that my daughter would not handle that well. When I brought up my concerns, I was told that they don't scope babies as their esophagus is generally too small for them to work on while the child is awake.
The whole exam lasted about 20 minutes from start to finish and the only difficulties encountered were the fasting measures (babies don't understand why they can't eat for a few hours) and a day or so later after the barium has worked its way through their bowels the bowel movements are definitely icky. That part (thankfully) only lasts a day or so and giving the baby plenty of fluids helps it to go faster.
My youngest daughter was 15 mo old when she had this procedure but she is the size of a 3-6 mo old baby weighing in at about 12 lbs. My oldest had this done at 2 1/2 mo of age weighing in at almost 6lbs. Both babies handled it well and it helped the Dr. know hot to better treat each of them.
Some questions you could ask your pediatric GI are the following:
Is it necessary to do the test now, or could it wait until the prevacid has had a chance to take effect?
What does this test help you to see to be able to give my child the best treatment possible?
Are there any risks involved?
What are possible causes of acid reflux? (The most common in infants tends to be a bovine protein intollerance or allergy, so he may suggest changing milk/formula/or your diet if you are breast feeding).
My oldest outgrew her acid reflux rather quickly. By about 6 to 8 months of age she no longer needed Zantac to control the reflux.
My youngest is a whole different case, but a lot of her issues are due to prematurity and the upper GI was needed for more than reflux issues.
If you have any questions or need help figuring out how to comfort him please feel free to contact me.
I do hope it all goes well!
A.