Mucosal fibrosis in intestinal transplant biopsies correlates positively with the development of chronic rejection

Update on Chronic Rejection After Intestinal Transplant: An Overview From Experimental Settings to Clinical Outcomes

Chronic rejection affects the long-term survival of solid-organ transplants, accounting for an incidence of between 5% and 10% after intestinal/multivisceral transplant. Because of unclear symptoms and signs and endoscopic findings, the diagnosis is often delayed. Presently, allograft removal represents the only available therapy due to the absence of effective pharmacologic approaches. Extensive research, through animal models, has been performed over the past 20 years to clarify the complex immune- and nonimmune-mediated mechanisms behind the development of chronic allograft enteropathy, with the aim of elucidating how to avert chronic rejection. The role of donor-specific antibodies and the way to challenge them in the clinic have gained acceptance among transplant centers as one of the main steps to prevent chronic rejection, although no common protocol exists that can be applied in a systematic fashion. The adjunct of a liver graft when retrans planting is needed in a sensitized recipient due to its protective effect against humoral immunity. Multicenter studies and clinical trials are required to better understand the pathogenesis of chronic rejection and to find the therapeutic answer to this clinical query.

Chronic Rejection After Intestinal Transplant: Where Are We in Order to Avert It?

Chronic rejection affects the long-term survival of all solid organ transplants and, among intestinal allografts, occurs in up to 10% of the recipients. The insidious clinical evolution of the chronic allograft enteropathy, the absence of noninvasive biomarkers, and the late endoscopic findings delay its diagnosis. No pharmacological approach has been proven effective, and allograft removal nowadays still represents the only available therapy. The inclusion of the liver in the visceral allograft appears to be the only intervention affecting the development of chronic rejection, as revealed by large-center studies and registry reports. A significant body of evidence emerged from the experimental setting and provided essential knowledge on the complex mechanisms behind the development of chronic allograft enteropathy. More recently, donor-specific antibodies have been suggested as an early, key element in the natural history of chronic allograft enteropathy and several novel approaches, tackling the antibody-mediated graft injury, have gained acceptance in clinical settings and are believed to impact on chronic rejection. The inclusion of a liver allograft is advocated when re-transplanting a sensitized recipient, due to its protective effect against humoral immunity. Multicenter trials are required to understand and tackle chronic rejection, and find the therapeutic answer to this clinical dilemma.

Updates on acute and chronic rejection in small bowel and multivisceral allografts

PURPOSE OF REVIEW

The surgical management of short bowel syndrome now includes intestinal (ITx) and multivisceral transplantation (MVTx), which has advanced and is now a sustainable option for the treatment of intestinal failure. Improvements in immunosuppressive therapies, excellence in surgical and medical management and enhanced post-transplant monitoring have all contributed to optimizing this solid organ transplant as a means of supplanting the diseased native bowel and alimentary tract with a functional alternative.

RECENT FINDINGS

Post-transplant management is a critical and challenging phase of gastrointestinal transplantation, and the transplant pathologist is an essential member of the transplant team who identifies many of the early and late complications after ITx and MVTx. Among the most injurious and common complications of ITx and MVTx is acute rejection and, to a lesser degree, chronic rejection. Both of these broad categories of rejection are principally identified by histopathological changes in the allograft; however, biomarkers and other laboratory analytes are rapidly evolving into critical ancillary tools in identifying and further characterizing the rejection process. Thus, the transplant pathologist must also be able to utilize numerous other laboratory tests and panels of molecular biomarkers that provide supplementary information to accompany the biopsy interpretation and clinical suspicion of rejection.

SUMMARY

Using biopsies and an assortment of additional approaches, the transplant pathologist is now able to provide swift and detailed information regarding the rejection process in the gastrointestinal transplant. This enables the clinical team to properly and successfully intercede, contributing to enhanced patient and graft survival.

Histologic analysis of chronic rejection in small bowel transplantation: mucosal and vascular alterations

BACKGROUND

Chronic rejection is a significant barrier to small bowel allograft survival. Although chronic rejection primarily involves vessels of the submucosa, serosa, and mesentery, some mucosal alterations have been suggested to be correlative.

METHODS

We retrospectively investigated explanted small bowel allografts for clinical characteristics and histological alterations in the mucosa, submucosa, and serosa.

RESULTS

Crypt epithelial mucin loss, submucosal fibrosis, and length of time to explant were all statistically associated with chronic rejection. Medium-sized and large-sized vessels of the serosa and mesentery preferentially demonstrated histologic changes of chronic rejection.

CONCLUSION

These results further define chronic vascular rejection and the relationship between the mucosal changes and chronic rejection.

Chronic rejection after combined liver and small bowel transplantation in a child with chronic intestinal pseudo-obstruction: a case report

An 11-year-old boy with irreversible intestinal failure secondary to chronic intestinal pseudo-obstruction (CIPO) and intestinal failure-associated liver disease (IFALD) underwent a combined en bloc reduced liver and small bowel transplantation. He was discharged home after 9 weeks on full oral intake without requiring intravenous nutritional or fluid supplementation. The first episode of mild acute rejection, which occurred 18 months after transplantation, was successfully treated with steroids. An episode of rotavirus gastroenteritis led to severe exfoliative rejection of the bowel graft, which was resistant to steroid and Infliximab treatment but responded to OKT3. There was associated Epstein-Barr virus viremia with no evidence of posttransplant lymphoproliferative disease. Another episode of moderate to severe acute liver rejection occurred 5 months later. At the same time, multiple biliary strictures were diagnosed and treated. Persistent clinical symptoms of abdominal pain and increased stomal output as well as atrophy of the ileal mucosa on several biopsies, suggested the possibility of chronic rejection (CR). A second combined whole liver and small bowel transplant was performed. The diagnosis of CR was confirmed on histology of the explanted graft. The postoperative course was severely complicated and 71 days after the retransplantation, the boy died because of respiratory failure and multiorgan failure. In summary, intestinal transplantation can be successfully performed in children with CIPO, giving them the opportunity to be free from total parenteral nutrition. As survival following intestinal transplantation continues to improve, the problem of CR has become increasingly important and the only treatment available is retransplantation, which is associated with poor outcomes.

The ?Blind Innsbruck Ostomy?, a cutaneous enterostomy for long-term histologic surveillance after small bowel transplantation

Intestinal transplantation has evolved into an established treatment for patients with intestinal failure. Although acute rejection episodes are reversible, late onset and chronic rejections remain major prognostic factors. We describe here our experience with endoscopic and histologic long-term monitoring through a cutaneous enterostomy. Between 1989 and 2003, 24 intestinal transplants were performed. After revascularization and reconstruction of proximal intestinal continuity, a side-to-end ileo-enterostomy was performed 20 cm from the stoma and the terminal allograft ileostomy left in the abdominal wall. Approximately after 2 months, in eight patients (nine transplants), the stoma was excluded from the gastrointestinal continuity, allowing ongoing endoscopy and histologic examination. Of 280 forceps biopsies, 64 (23%) were performed through the 'blind ostomy'. Eleven acute allograft rejections were diagnosed between days 3 and 51, with two episodes in three cases. Through the 'blind ostomy', a late mild acute rejection was diagnosed in five instances, three to 37 months after transplantation. In all these patients, basal immunosuppression was intensified. Chronic rejection was seen in three cases 4-26 months after transplantation. In one of the three patients, chronic rejection was diagnosed from the excluded blind enterostomy. A long-term cutaneous enterostomy, even if disconnected from the intestinal continuity, enables simple long-term monitoring of small bowel allografts.