Progress towards Human Anorectal Transplants

A new study indicates that human anorectal transplantation is possible anatomically and technically. They anticipate our study will aid in the potential future application of this procedure to human patients.

There has been a lot of discussion recently about progress towards human head or technically full body transplantation (full body transplantation from the neck down would include anorectal transplantation).

Anorectal transplantation is a method for patients who have lost their anorectal function or suffer from congenital anorectal dysfunction to recover this function, and this has been investigated in experimental animal models using pigs, dogs, and rats. In this study, we performed an examination of anorectal transplantation in human cadavers to investigate whether this procedure could be performed in patients.

Picture at the very bottom of the article. Not pretty. Do not go there if you do not want to see it

There are of course valid and wonderful quality of life improvements that this technology could enable.

However, I will briefly make a reference the first season of South Park. [Let me know if you can find a video clip of the South Park scene.

“Here is a monkey with four asses. And here of course is my four-assed ostrich and four-assed mongoose.”
– Mafesto

Anorectal function is constituted in a composite manner by various structures such as the rectum, anal canal, levator ani, and anal sphincter muscle, which is innervated by PNs. The muscular transfer of the gracilis or the gluteus maximus muscles and the implantation of an artificial sphincter have previously been performed to recover anal function. However, none of these procedures are considered ‘gold standard’ techniques due to the complex nature of anorectal functions. Anorectal transplantation seems to be a supreme method allowing for reconstruction of anal function, which is advantageous over other methods. This is the first report describing mock anorectal transplantation in a human cadaver. Since two human cadavers were fixed by the Thiel method, the flexibility of the joints was well preserved and it was easy to take the appropriate positions for the operation.

In this study, the IMA, IMV, PNs, PAs, and PVs were obviously detected in both the donor and recipient cadavers (Figure 1-A, B Figure 2-C). The length and diameter of the IMA, IMV, PNs, PAs, and PVs were sufficient to allow anastomoses without tension. Our previous experiment in dogs revealed that the anastomoses of PNs, PAs, and PVs had an important role in the success of anorectal transplantation [12]. A previous study in humans described the length of the PNs passing out below the sacrotuberous ligament as being varied from 21 to 44 mm (median, 29.5 mm). The diameter of the PAs in our human cadaver was thinner than the previously reported human data (2.7 ± 0.4 mm at right and 2.7 ± 0.5 mm at left). This could be because in cadavers, vessels are collapsed and lack elasticity and turgor, and nerves are easily dried during dissection. These data indicated that the anastomoses of the IMA, IMV, PNs, PAs, and PVs were technically possible in human anorectal transplantation. In addition, the levator ani muscle could be strongly sutured to the pelvic wall to avoid graft ptosis. In this initial study, the warm ischemia time was about one hour from vessel clamps of the IMA and IMV to de-clamp of them after anastomoses. We anticipate that it will also be about one hour in clinical practice and the cold ischemia time including perfusion and transport will take in total ischemia time. The warm/cold ischemia time in intestinal transplantation is about 40 minutes/ 7 hours. The ischemia times of other composite tissue allografts were 5 h 10 min (cold) in hand, 2 h and 40 min in face, and 10 hours (cold) in larynx. These times will fit within the range of acceptable ischemia time for anorectal transplantation. As a result, we performed mock anorectal transplantation from a deceased donor into a recipient after abdominoperineal excision.

The clinical application of anorectal transplantation is not only limited to anal dysfunction resultant from post-abdominoperineal excision, but also that caused by anal atresia, Hirschsprung’s disease, intractable anal fistulas, or trauma. And still farther, it may be accompanied en bloc colon and small bowel transplantation. Therefore, it is necessary to develop appropriate transplantation and reconstruction methods for various defects. Evidently, the postoperative anorectal function must also be examined in detail. It is well known that the PVs provide the majority sensations and functions of the anorectum. In our preliminary study using dogs, anorectal function recovery could be observed at six months after re-anastomoses of the PVs (data not shown). And also, the use of immunosuppressants is required to control transplant infection and rejection. To confirm these, it is necessary to perform long-term observations after anorectal allotransplantation in experimental animals such as dogs or monkeys. It has been thought that anorectal transplantation is practically difficult in the clinical setting. However, considering recent advances in operational techniques and transplantation medicine, anorectal transplantation may follow the success of other vascularized composite allotransplants in humans, including those of the limb, face, larynx, and uterus

Picture of anorectal transplant below. Do not scroll further if you do not want to see it

SOURCE – PLOS One

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