Baby boy with UTI (PROPHYLACTIC anti biotics before VCUG and DMSA?)

My son is 5.5 months now. He had his first UTI when he was 4 months old
with mild symptons. He was treated and went for an Ultrasound check. It
shows fine. Recently I went to the hospital and checked his urine again
just to see if everything is alright now. The report shows he has UTI
AGAIN! He has no symptons. However he is being treated again. Now the
pediatrician wants him to have a VCUG (to check if it's a 'reflux') in
3 weeks and a DMSA (kidney function and if it has been scared) in 6
months. Here are questions.

1. He is un-circumcised, should we remove his foreskin before VCUG ?
how long does it take to heal?
2. Is it necessary to take prophylactic anti biotics until they rule
out the internal problems?
3. What's the side effect of prophylactic? If he becomes resistant to
one kind of prophylactic, will he be resistant to any other ones?
4. Should we sedate him for VCUG?

We are SOOO worried about him and I hope someone here can offer some
help, so that we can make a better solution for him. Thanks!

1. He is un-circumcised, should we remove his foreskin before VCUG ?
how long does it take to heal?

Not necessary.

2. Is it necessary to take prophylactic anti biotics until they rule
out the internal problems?

That is the American Academy of Pediatric's guidelines

3. What's the side effect of prophylactic? If he becomes resistant to
one kind of prophylactic, will he be resistant to any other ones?

People do not become immune to an antibiotic. The bacteria do. There
is a risk that being on prophylactic antibiotics will "select"
resistant bacteria.

4. Should we sedate him for VCUG?
VCUG should not be done while under sedation.

Chris
Pediatrician