My daughter had one when she was still an infant. Can’t remember exact age.  They did not put her to sleep and we did not give extra cortef. It was pretty stressful and uncomfortable for her in the beginning. It did allow them to see where her vaginal canal came in and how her bladder, etc. was. We could see the images as they were taken and they explained each image to us so we knew what they were looking at.  I believe the urologist used some of this information to prepare for surgery. I don’t have any regrets having this done. I hope that helps. Just remember that it was a very temporary discomfort mainly when the catheter is inserted. I wish you and your daughter the best.