My daughter had this procedure...I don’t remember what is was called...and she wasn’t sedated (which she should have been as she was very upset by it). They cathed her and filled her bladder with dye and then tracked it as she urinated. It wasn’t painful, but she was only 5 and scared. I believe they wanted to make sure the urinary pathway in correct. Her urethra is located inside her vagina...which they said is not very unusual.