The success of more contemporary approaches was challenged by Thomas in 2004: "confidence in the superiority of modern surgery is almost certainly misplaced as the crucial components of current clitoral reduction surgery are not fundamentally different from those used in specialist centres 20 years ago". Vaginoplasty, the construction or reconstruction of a vagina, can be fairly simple or quite complex, depending on the initial anatomy. If a normal internal uterus, cervix and upper vagina (the Müllerian derivatives) exist, and the outer virilization is modest, surgery involves separating the fused labia and widening the vaginal introitus. With greater degrees of virilization, the major challenge of the procedure is to provide a passage connecting the outer vaginal opening to the cervix which will stay wide enough to allow coitus. XY girls or women with partial androgen insensitivity syndrome will have a blind vaginal pouch of varying degrees of depth. Sometimes this can be dilated to a usable depth. Sometimes surgery is performed to deepen it. The most challenging surgery with the highest complication rate is construction of an entirely new vagina (a "neovagina"). The most common instance of this is when a child will be assigned and raised as a female despite complete virilization, as with Prader 5 CAH, or (in the past) when a genetic male infant with a severely defective penis was reassigned as a female. One method is to use a segment of colon, which provides a lubricated mucosal surface as a substitute for the vaginal mucosa. Another is to line the new vagina with a skin graft. Potential surgical problems: Stenosis (narrowing) of the constructed vagina is the most common long-term complication and the chief reason that a revision may be required when a girl is older. When a neovagina is made from a segment of bowel, it tends to leak mucus; when made with a skin graft, lubrication is necessary. Less common complications include fistulas, uncomfortable scarring, and problems with urinary continence. Gonadectomy is removal of the gonads. If the gonads are dysgenetic testes or streak gonads and at least some of the cells have a Y chromosome, the gonads or streaks must be removed because they are nonfunctional but have a relatively high risk of developing gonadoblastoma. If the gonads are relatively "normal" testes, but the child is to be assigned and raised as female, (e.g., for intersex conditions with severe undervirilization, or major malformations involving