Allogeneic anorectal transplantation in rats: technical considerations and preliminary results

Microsurgical Technique and Results of Anorectal Transplantation in the Rat

Anorectal transplantation (ART) is an obvious therapeutic option for treating permanent colostomy and severe fecal incontinence. The rat is the best model for beginning studies of a new surgical procedure. In this article, we review ART techniques in rats.

METHODS

We reviewed articles on rat and ART keywords throughout Cochrane Library, MEDLINE, and EMBASE. Five articles were found, of which 2 used autotransplantations, 1 performed only transplantation of the anal canal and extraperitoneal rectum, and another performed transplantation of the entire intestine, including the anus, but only followed for 2 hours.

RESULTS

In 2016, we performed the first series of isoART (n = 6) and alloART (n = 9) of the entire anorectal segment and micro-anastomosis of the inferior mesenteric vessels. Two animals died due to surgical complications, and the others survived until the endpoint of the experiment. Five animals with alloART showed clinical signs of immunologic rejection 3 weeks after transplantation, and autopsy histology on postoperative day 30 revealed moderate to severe rejection in the allografts.

CONCLUSIONS

In this review, we observed that ART in rats is viable and may allow further physiologic and immunologic studies of this procedure, a potential treatment for severe incontinence and permanent colostomy.

Multivisceral transplantation of pelvic organs in rats

Background

Multivisceral transplantation of pelvic organs would be a potential treatment for severe pelvic floor dysfunction with fecal and urinary incontinence, extensive perineal trauma, or congenital disorders. Here, we describe the microsurgical technique of multivisceral transplantation of pelvic organs, including the pelvic floor, in rats.

Donor operation

We performed a perineal (including the genitalia, anus, muscles, and ligaments) and abdominal incision. The dissection progressed near the pelvic ring, dividing ligaments, muscles, external iliac vessels, and pudendal nerves, allowing pelvic floor mobilization. The aorta and vena cava were isolated distally, preserving the internal iliac and gonadal vessels. The graft containing the skin, muscles, ligaments, bladder, ureter, rectum, anus and vagina, uterus and ovarian (female), or penile, testis and its ducts (male) was removed en bloc, flushed, and cold-stored.

Recipient operation

The infrarenal aorta and vena cava were isolated and donor/recipient aorta-aorta and cava-cava end-to-side microanastomoses were performed. After pelvic floor and viscera removal, we performed microanastomoses between the donor and the recipient ureter, and the rectum and pudenda nerves. The pelvic floor was repositioned in its original position (orthotopic model) or the abdominal wall (heterotopic model). We sacrificed the animals 2 h after surgery.

Results

We performed seven orthotopic and four heterotopic transplantations. One animal from the orthotopic model and one from the heterotopic model died because of technical failure. Six orthotopic and three heterotopic recipients survived up to 2 h after transplantation.

Conclusion

The microsurgical technique for pelvic floor transplantation in rats is feasible, achieving an early survival rate of 81.82%.

Anorectal Transplantation: The First Long-term Success in a Canine Model

OBJECTIVE

Anorectal transplantation is a challenging procedure but a promising option for patients with weakened or completely absent anorectal function.

SUMMARY BACKGROUND DATA

We constructed a canine model of anorectal transplantation, evaluated the long-term outcomes, and controlled rejection and infection in allotransplantation.

METHODS

In the pudendal nerve function study, 6 dogs were randomly divided into 2 groups, transection and anastomosis, and were compared with a control using anorectal manometry, electromyography, and histological examination. In the anorectal transplantation model, 4 dogs were assigned to 4 groups: autotransplant, allotransplant with immunosuppression, allotransplant without immunosuppression, and normal control. Long-term function was evaluated by defecography, videography, and histological examination.

RESULTS

In the pudendal nerve function study, anorectal manometry indicated that the anastomosis group recovered partial function 6 months postoperatively. Microscopically, the pudendal nerve and the sphincter muscle regenerated in the anastomosis group. Anorectal transplantation was technically successful with a 3-stage operation: colostomy preparation, anorectal transplantation, and stoma closure. The dog who underwent allotransplantation and immunosuppression had 2 episodes of mild rejection, which were reversed with methylprednisolone and tacrolimus. The dog who underwent allotransplantation without immunosuppression had a severe acute rejection that resulted in graft necrosis. Successful dogs had full defecation control at the end of the study.

CONCLUSIONS

We describe the critical role of the pudendal nerve in anorectal function and the first long-term success with anorectal transplantation in a canine model. This report is a proof-of-concept study for anorectal transplantation as a treatment for patients with an ostomy because of anorectal dysfunction.