Small bowel transplantation

A practical guide for small bowel transplantation in rats-review of techniques and models

BACKGROUND

Animal models are a central aspect in research on small bowel transplantation (SBTx). Among them, rats are the preferred species because of their widespread availability and cost effectiveness. Because the complexity of the surgical procedure could per se influence the outcome of an experiment, a standardized and comparable technique is important. Based on of the vast amount of different models and surgical techniques published to this point, a review seemed necessary to guide investigators when choosing the suitable model.

MATERIALS AND METHODS

A systematic literature search of original articles published between 1965 and 2016 using the Medline Database regarding techniques of SBTx in rats was conducted according to the Preferred reporting Items for Systematic Reviews and Meta-Analyses guidelines. Articles describing a new technique or evaluating different techniques were considered.

RESULTS

A total of 38 publications fulfilled the selection criteria and were included. Data from these publications were regarded as too heterogeneous for statistical analysis. Depending on graft length and placement, full-length and reduced length heterotopic and orthotopic models were differentiated. Important factors concerning a good survival rate are the chosen model (heterotopic has a better outcome compared with orthotopic), a vascular flush of the graft in situ, a careful luminal flush of the graft, adequate fluid resuscitation, and a warm ischemia time of less than 40 min.

CONCLUSIONS

SBTx in rats remains a complex and challenging procedure, which necessitates a standardized technique as well as sufficient training. By choosing the optimal experimental model, applying established strategies, and proven techniques, a standardized and scientifically reliable model can be achieved.

Is portal venous outflow better than systemic venous outflow in small bowel transplantation? Experimental study in syngeneic rats

BACKGROUND/PURPOSE

Blood drainage of the graft into the recipient portal vein reestablishes the physiological venous outflow after small bowel transplantation (SBT). However, although this approach is likely beneficial for the host, it may be technically more demanding making portocaval venous drainage the preferred arrangement during human SBT. The aim of this study was to examine in a syngeneic model of SBT the possible benefits of portoportal anastomosis (PPA) vs portocaval anastomosis (PCA) in terms of body and organ weights and bacterial translocation.

METHODS

Syngeneic SBT was carried out in 25 Brown-Norway male rats weighing 249 +/- 17.5 g using either PPA (n = 13) or PCA (n = 12). Half the animals in each group were killed, respectively, on postoperative day 2 or 7. Liver, spleen, and lungs were weighed and under sterile conditions the regional lymph nodes were excised. The nodes and venous samples from the cava and portal veins were cultured for aerobes and anaerobes. Bacterial components were detected in blood by polymerase chain reaction. The findings in both groups were compared by chi2 or Mann-Whitney U tests.

RESULTS

Mean postoperative body weight change was -3.6% +/- 1.5% in PPA and -6.0% +/- 1.2% in PCA animals (ns) on day 2 and -6.5% +/- 2.6% and -8.0% +/- 5.0% (ns) on day 7. Liver, spleen, and lung weights were not significantly different between both groups on either end point. Gram-negative enteric bacteria were found in 3 of 7 PCA animals and 2 of 6 PPA animals at day 2 (ns) and in 1 of 6 and 4 of 6 on day 7 (ns). Aerobic gram-positive bacteria were found in 1 of 7 and 1 of 6 (ns), 3 of 6 and 3 of 6 (ns), respectively, in the 4 groups. Most positive cultures corresponded to portal blood and lymph node samples. There were no anaerobic growths.

CONCLUSIONS

-No body or organ weight change suggesting significant functional advantages of one technical alternative over the other could be demonstrated. -Bacterial translocation in the absence of rejection was frequent after SBT independently of the variety of venous outflow used. No difference in bacterial translocation between both anastomosis could be demonstrated. -Orthotopic venous drainage did not seem to be advantageous in the present experimental setting.

Segmental small bowel transplantation in the rat: comparison of lipid absorption between jejunal and ileal grafts

BACKGROUND

From the immunological point of view, it is very important to evaluate the efficacy of segmental small bowel transplantation and to determine which part of the intestine, jejunum, or ileum should be used. In the present study, we investigated the absorptive function of the transplanted jejunum and ileum in the rat.

METHODS

Syngeneic segmental small bowel transplantation (jejunal or ileal grafting) was performed. After surgery, body weight and fecal fat excretions were measured. In addition, bile acid concentration in bile juice was measured, and the response of both serum lipase and bile flow rate after oleic acid stimulation was evaluated. Recanalization of the lymphatic vessels was investigated by lymphangiography.

RESULTS

There was no significant difference in body weight change between normal controls, jejunum-transplanted rats, and ileum-transplanted rats. In short gut rats, however, body weight was significantly impaired. Fecal fat excretion in short gut rats was the highest in the four groups, and it was significantly lower in ileal grafts than in jejunal grafts. Ileum-transplanted rats also showed a significantly higher bile acid concentration in bile juice than jejunum-transplanted rats. After oleic acid stimulation, serum lipase responded better in ileal transplants than in jejunal transplants, but the bile flow rate did not show significant change in either group. Recanalization of the lymphatic vessels was established on the 28th postoperative day.

CONCLUSIONS

These results clearly show that ileal transplantation is more conducive to lipid absorption than jejunal transplantation.

Small bowel transplantation in rats: endoscopic and histological evaluation of graft rejection

Heterotopic small bowel transplantation was performed using the cuff technique in DA(RT1a) to PVG(RT1c) rat fully allogeneic combination. In this model, the rejection course of the grafted intestine was evaluated endoscopically via double stomata and was classified into four stages. Early changes appeared on postoperative day 3. Stage I: The mucosa of the grafted intestine showed patchy paleness and loss of the capillary fine network patterns, accompanied by microerosions. Closer examination revealed irregularity of the epithelial height and arrangement. Stage II: The damage spread progressively over the entire mucosa on day 4-5. Stage III: On day 6-7, the necrotic epithelium became detached, showing multiple ulcers which provoked hemorrhagic enteritis. Stage IV: Graft rejection was completed with total necrosis and white scar tissue formation by day 10-14. These endoscopic findings of the mucosa of the grafted intestine corresponded closely to the time course of pathological examinations. We conclude that endoscopic examination of grafted intestine may be an effective diagnostic tool to detect the rejection phenomenon at an early stage, as well as a simple tool to use for postoperative follow-up in combination with pathological examination.