Sex Change Operations

No, I’m not thinking about getting one. I just have a curiousity question regarding the doctors that do them.

What type of doctor is authorized to do gender reassaignment operations? It seems like they would have to have extensive training in gynecology, urology, plastic surgery, and general surgery. How would a doctor get the training necessary to do the operation; for instance do surgery residents usually experience this type of operation? Also, are there regulations as to what credientals a doctor must have to do the operation?

From this site, it appears a general surgeon did the operation numerous times, and he was only guided by a couple drawings.