The development of a canine anorectal autotransplantation model based on blood supply: a preliminary case report

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.

Identification of intra-abdominal lymphatics in canine carcasses by laparoscopic fluorescence lymphography with intradermal and intrapopliteal ICG administration

Objective

To evaluate the feasibility of laparoscopic fluorescence lymphography (LFL) using indocyanine green (ICG) via intradermal (ID) or intrapopliteal (IPP) administration in an ex vivo canine model.

Methods

Six thawed adult male dog carcasses were placed in the Trendelenburg position after placing three surgical ports in triangulation. ICG (0.5 mg/ml; 0.05 mg/kg) was administered to five of the carcasses (one carcass was a pilot) via ID in the left torso and IPP (right position, by surgical access) to stain the lymphatic pathway and medial iliac lymph node (MILN). Fluorescence quality, staining time, structures stained, and lymph node histopathology were assessed. Thoracic duct staining was also evaluated.

Results

ID administration showed staining of parts of the lymphatic pathway of the iliosacral lymph center in all cases using a single dose of ICG, with left MILN visualization in four carcasses. IPP administration showed staining of the right MILN in all cases, using a single dose in four carcasses. ICG reached the thoracic duct in one case. The two administration routes showed similar results in terms of required ICG volume, staining time, and visualization quality, although IPP was more effective in staining the MILN.

Conclusions

This study confirms the feasibility of staining the iliosacral lymph center (mainly the MILNs) by LFL in thawed dog carcasses via ID or IPP administration of ICG. However, the IPP route showed greater effectiveness in staining the MILN.

Hydrodynamics of defecation

Animals discharge feces within a range of sizes and shapes. Such variation has long been used to track animals as well as to diagnose illnesses in both humans and animals. However, the physics by which feces are discharged remain poorly understood. In this combined experimental and theoretical study, we investigate the defecation of mammals from cats to elephants using the dimensions of large intestines and feces, videography at Zoo Atlanta, cone-on-plate rheological measurements of feces and mucus, and a mathematical model of defecation. The diameter of feces is comparable to that of the rectum, but the length is double that of the rectum, indicating that not only the rectum but also the colon is a storage facility for feces. Despite the length of rectum ranging from 4 to 40 cm, mammals from cats to elephants defecate within a nearly constant duration of 12 ± 7 seconds (N = 23). We rationalize this surprising trend by our mathematical model, which shows that feces slide along the large intestine by a layer of mucus, similar to a sled sliding down a chute. Larger animals have not only more feces but also thicker mucus layers, which facilitate their ejection. Our model accounts for the shorter and longer defecation times associated with diarrhea and constipation, respectively. This study may support clinicians use of non-invasive procedures such as defecation time in the diagnoses of ailments of the digestive system.

ICG fluorescence imaging for quantitative evaluation of colonic perfusion in laparoscopic colorectal surgery

BACKGROUND

Fluorescence technology with indocyanine green (ICG) provides a real-time assessment of intestinal perfusion. However, a subjective evaluation of fluorescence intensity based on the surgeon's visual judgement is a major limitation. This study evaluated the quantitative assessment of ICG fluorescence imaging in determining the transection line of the proximal colon during laparoscopic colorectal surgery.

METHODS

This is a retrospective analysis of a prospectively maintained database of 112 patients who underwent laparoscopic surgery for left-sided colorectal cancers. After distal transection of the bowel, the specimen was extracted extracorporeally and then the proximal colon was divided within the well-perfused area based on the ICG fluorescence imaging. We evaluated whether quantitative assessment of intestinal perfusion by measuring ICG intensity could predict postoperative outcomes: F _max, T _max, T _1/2, and Slope were calculated.

RESULTS

Anastomotic leakage (AL) occurred in 5 cases (4.5%). Based on the fluorescence imaging, the surgical team opted for further proximal change of the transection line up to an "adequate" fluorescent portion in 18 cases (16.1%). Among the 18 patients, AL occurred in 4 patients (4/18: 22.2%), whereas it occurred in only 1 case (1/94: 1.0%) in the good perfusion patients who did not need proximal change of the transection line. The F _max of the AL group was less than 52.0 in all 5 cases (5/5), whereas that of the non-AL group was in only 8 cases (8/107): with an F _max cutoff value of 52.0, the sensitivity and specificity for the prediction of AL were 100 and 92.5%, respectively. Regarding postoperative bowel movement recovery, the T _max of the early flatus group or early defecation group was significantly lower than that of the late flatus group or late defecation group, respectively.

CONCLUSIONS

ICG fluorescence imaging is useful for assessing anastomotic perfusion in colorectal surgery, which can result in more precise operative decisions tailored for an individual patient.

Allogeneic anorectal transplantation in rats: technical considerations and preliminary results

Fecal incontinence is a challenging condition with numerous available treatment modalities. Success rates vary across these modalities, and permanent colostomy is often indicated when they fail. For these cases, a novel potential therapeutic strategy is anorectal transplantation (ATx). We performed four isogeneic (Lewis-to-Lewis) and seven allogeneic (Wistar-to-Lewis) ATx procedures. The anorectum was retrieved with a vascular pedicle containing the aorta in continuity with the inferior mesenteric artery and portal vein in continuity with the inferior mesenteric vein. In the recipient, the native anorectal segment was removed and the graft was transplanted by end-to-side aorta-aorta and porto-cava anastomoses and end-to-end colorectal anastomosis. Recipients were sacrificed at the experimental endpoint on postoperative day 30. Surviving animals resumed normal body weight gain and clinical performance within 5 days of surgery. Isografts and 42.9% of allografts achieved normal clinical evolution up to the experimental endpoint. In 57.1% of allografts, signs of immunological rejection (abdominal distention, diarrhea, and anal mucosa inflammation) were observed three weeks after transplantation. Histology revealed moderate to severe rejection in allografts and no signs of rejection in isografts. We describe a feasible model of ATx in rats, which may allow further physiological and immunologic studies.

Functional outcome of autologous anorectal transplantation in an experimental model

BACKGROUND

Although anorectal transplantation is a challenging procedure, it is a promising option for patients who have completely lost anorectal function or in whom it failed to develop, as in congenital malformations. The paucity of animal models with which to test functional outcomes was addressed in this study of anorectal manometry in rats.

METHODS

Wistar rats were assigned randomly to four groups: orthotopic anorectal transplantation, heterotopic transplantation, sham operation, or normal control. Bodyweight and anal pressure were measured immediately before and after operation, and on postoperative days 7 and 14. ANOVA and Tukey's test were used to compare results for bodyweight, anal manometry and length of procedure.

RESULTS

Immediately after the procedure, mean(s.d.) anal pressure in the orthotopic group (n = 13) dropped from 31·4(13·1) to 1·6(13·1) cmH2 O (P < 0·001 versus both sham operation (n = 13) and normal control (n = 15)), with partial recovery on postoperative day 7 (14·9(13·9) cmH2 O) (P = 0·009 versus normal control) and complete recovery on day 14 (23·7(12·2) cmH2 O). Heterotopic rats (n = 14) demonstrated partial functional recovery: mean(s.d.) anal pressure was 26·9(10·9) cmH2 O before operation and 8·6(6·8) cmH2 O on postoperative day 14 (P < 0·001 versus both sham and normal control).

CONCLUSION

Orthotopic anorectal transplantation may result in better functional outcomes than heterotopic procedures. Surgical relevance Patients with a permanent colostomy have limited continence. Treatment options are available, but anorectal transplantation may offer hope. Some experimental studies have been conducted, but available data are currently insufficient to translate into a clinical option. This paper details functional outcomes in a rat model of anorectal autotransplantation. It represents a step in the translational research that may lead to restoration of anorectal function in patients who have lost or have failed to develop it.

Anorectal autotransplantation in a canine model: the first successful report in the short term with the non-laparotomy approach

Colostomy is conventional treatment for anal dysfunction. Recently, a few trials of anorectal transplantation in animals have been published as a potential alternative to colostomies; however, further development of this technique is required. In this study, we utilized a canine model of anorectal transplantation, evaluated the patency of our microsurgical anastomoses, and assessed the perfusion of the transplanted anus. We designed a canine anorectal transplantation model, wherein anorectal autotransplantation was performed in four healthy beagle dogs by anastomoses of the lower rectum, the bilateral pudendal arteries (PAs) and veins (PVs), and pudendal nerves (PNs). Postoperative graft perfusion was measured by indocyanine green (ICG) angiography and histological examination. The length of the anorectal graft including perianal skin, anal sphincter muscle, bilateral PAs, PVs, and PNs was 4.9 ± 0.3 cm. All diameters of the PAs, PVs, and PNs were large enough to be microscopically anastomosed. Both ICG angiography and histological examination demonstrated good graft perfusion, except for one case that lead to venous congestion. These results show that anastomosis of the bilateral PAs, PVs, and PNs is required for anorectal transplantation. This is the first successful report of canine anorectal autotransplantation.

Anorectal transplantation in human cadavers: mock anorectal allotransplantation

BACKGROUND

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.

METHODS

A 77-year-old woman cadaver 1 was used as the donor and a 98-year-old woman cadaver 2 was used as the recipient. Initially, abdominoperineal excision of the anus and rectum (the Miles' operation) was performed on the recipient. Next, an anorectal graft containing the pudendal nerve (PN), pudendal artery (PA), pudendal vein (PV), inferior mesenteric artery (IMA), and inferior mesenteric vein (IMV) was harvested from the donor. The donor graft was transplanted into the recipient by intestinal anastomosis and microneurovascular anastomoses orthotopically.

RESULTS

The diameters of the PN (right/left), IMA, and IMV were 2.5 mm/2.5 mm, 2.0 mm, and 1.5 mm, respectively, in cadaver 1, and 2.0 mm/2.0 mm, 2.0 mm, and 2.0 mm, respectively, in cadaver 2. The length of the PN, PA, PV, IMA, and IMV in the graft was sufficient to allow proper anastomosis.

CONCLUSION

This preliminary study indicated that human anorectal transplantation was possible anatomically and technically. We anticipate our study will aid in the potential future application of this procedure to human patients.