Bizarrely, I'm writing this from my hospital bed in Thailand where I am recovering from a minor cosmetic revision 8 months after my SRS. I think I can answer some of your questions, hopefully.
Sigmoid colon vaginoplasty carries greater risks. You are effectively removing a section of colon to extend the distal (deep) end of the vagina. The surgeon must then re-graft the two colon sections back together so your bowel works properly. Because the colon is mucosal, it is stretchier than skin, is naturally moist and lubricates. However, using internal organs is a much higher risk than using skin which is superficial and plastic. Internal bowel problems can create major life threatening illnesses. Some patients complain of the smell, but I can't comment on this. Some surgeons will only use the colon approach if it's impossible to harvest skin from elsewhere on the body.
A lot of surgeons are also now considering a perioneatal graft as an alternative to colon, because it is more superficial tissue, is very stretchy, and apparently regrows very fast. It is a new technique and and still emerging.
Cosmetically, you will not be able to tell the difference between colon and skin graft SRS unless you are using a speculum to look into the deepest part of the vaginal vault. The penile tissue covers the first few inches of depth.
Proper construction of a fourchette seems to be tough for any surgeon, and I've yet to figure out why. I suspect it has to do with how the tissue contracts as it heals. I've yet to see an SRS in which the labia fully surrounds the vulva - although I know plenty of ciswomen whose labia is not completely circumferential too.
You also asked about two stage SRS, performing orchiectomy and penile inversion in a separate stage to the distal graft. Dr Sanguan uses this technique. He will perform the initial inversion and pack the internal orifice for one week. Scrotal tissue is taken to a lab, where it is kept alive for one week, during which time it is scrapped and cleaned, all the hair follicles removed, and prepared for grafting. The patient's vaginal opening is heavily packed in aseptic technique, and vacuum pressure is used to drain the wound. After one week in bed, the patient returns to surgery and Dr Sanguan will perform the full thickness skin graft. The surgeon will assess in advance if there is sufficient scrotal skin for the depth needed. If not, they will discuss options to take skin from another part of the body - usually the high inner thigh where the underwear line is.
I encourage you to be mindful when looking at photos. When you walk out of hospital, you do not have a shiny new sex organ. You have a huge, invasive wound that will heal into a vagina over many months and years. The photos are radically different between 1 week, 1 month, 6 months, 1 year and 5 years. It takes about three months for the incisions to heal into scarlines, and about 6-9 months for them to become un-noticeable. It takes a good year or three for all the sub-cutaneous fat to settle under the skin graft and the pubic mound to settle into a normal shape.
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