Intestinal transplantation (ITx) has increasingly become an accepted treatment option for patients with irreversible intestinal failure. The short-term outcome of ITx has improved over the past decade because of the advancements in surgical techniques, immunosuppressive agents, antimicrobial drug therapy, and so on.1-3 However, the long-term outcome of ITx continues to be lower than that of other solid organ transplants.4 With current immunosuppression, risk of acute rejection is reduced but chronic allograft injury remains a major cause of late graft loss.5 As the number of intestinal transplants performed per year has steadily increased, the proportion of patients likely to suffer chronic rejection and subsequent graft loss has also increased. In these instances, retransplantation is a viable treatment option for patients with primary graft loss.
Intestinal retransplantation has been associated with significant graft loss and patient mortality.6,7 Historically, attention has mostly been focused on T cell–mediated cellular mechanisms to explain such poor outcomes, whereas, the impact of antibody-mediated mechanisms has been less recognized than other organs. Recent publications strongly indicate that the presence of human leukocyte antigen (HLA) donor-specific antibody (DSA) and non-HLA antibodies are associated with increased incidence and severity of intestine allograft rejection and poor prognosis for graft and patient.8-12 It has been well documented that the presence of a liver component in an intestinal graft is associated with improved graft survival.13,14 With the advent of more specific and sensitive assays, improved HLA antibody clearance, particularly for de novo DSA, has been implicated as a potential mechanism contributing to improved outcomes with simultaneous liver grafting.8
Similar to any other solid-organ transplant procedures, the recipients become sensitized after primary intestinal graft loss. With the immunoprotective role of the liver, we hypothesized that the short-term and long-term outcomes may be better after liver-inclusive retransplantation. The purpose of this study was to review our 10-year experiences with adult intestinal retransplantation and to evaluate the outcomes of liver-free and liver-inclusive retransplantations.
A total of 212 adult patients underwent primary ITx during our study period. Twenty-four (10.2%) underwent retransplantation and 23 were included in the final analysis. Of these patients, 13 (56.5%) received liver-free retransplantations including small bowel (SB) (n = 12) and modified multivisceral graft (MMV) (n = 1) and 10 (43.5%) received liver-inclusive retransplantations.
The primary diagnoses in 23 retransplanted patients were Crohn disease (n = 5), superior mesenteric thrombosis (n = 5), intestinal volvulus (n = 3), Gardner syndrome (n = 2), intestinal pseudo-obstruction (n = 2), and other causes (n = 6). The median age of recipients was 37.0 years (range, 19.0–60.0 years) at primary ITx. The initial transplant graft was SB (n = 16), MMV (n = 6), and multivisceral graft (MV) (n = 1). After transplantation, the average number of episodes of acute rejection (≥mild grade) experienced per patient during the first year was 2.39 (median, 2; range, 0–7). The median onset of the first episode of acute cellular rejection (ACR) was 23 days (range, 6–298 days) after transplantation, and the majority of the first acute episodes occurred within the first 3 months. Three subjects (13.0%) had zero rejection episodes. The median time of primary graft survival was 15.5 months (range 2.7 to 67.4 months). The most common cause of primary graft failure was chronic rejection (n = 16), followed by ACR (n = 4), acute humoral rejection (n = 1), infection (n = 1), and unknown etiology (n = 1). The patient demographics and pretransplant diagnoses at primary transplantation are summarized in Table 1.
At primary ITx, the median levels of pretransplant panel reactive antibody (PRA) class I and PRA class II were 10.0% (range, 0%–100%) and 4.0% (range, 0%–100%), respectively. Complete T/B lymphocytotoxic cross-match (CDC-XM) was positive in seven cases (30.4%) and negative in 16 cases (69.6%). Determination of specificities of preformed HLA antibodies was conducted in 11 cases, in which DSA was positive in four (17.4%), negative in Seven (30.4%) and unknown in 12 (52.2%). Posttransplant antibody monitoring was performed in 14 cases, in which de novo DSA was positive in nine (39.1%) before enterectomy (n = 4) or after enterectomy (n = 5) and unknown in 14 (60.9%). Posttransplant DSA was detected in two cases but pretransplant antibody status was unknown.
The median time interval between primary transplantations and retransplantations was 26.4 months (range, 5.1–67.4 months). After primary graft failure, the median time interval between enterectomy and retransplantation was 8.5 months (range, 2.9 to 22.5 months) in 16 of 23 (69.6%) patients, and immediate retransplantation after enterectomy was performed in seven of 23 (30.4%) patients.
Patient and Graft Survival After Retransplantation
With an average follow-up of 37.7 months (range, 8.4–86.2 months), the Kaplan-Meier estimated survival rates at 1, 3, and 5 years for retransplantations were 90.9%, 67.1%, and 59.7% (patient) and 82.2%, 58.6%, and 51.3% (graft), respectively. For primary transplants, the survival rates at 1, 3, and 5 years were 89.5%, 73.3%, and 61.8% (patient) and 85.1%, 63.2%, and 52.1% (graft), respectively. Both the patient and graft survival rates in primary transplants were similar to the rates in retransplantations (P = 0.64 and P = 0.71, respectively) (Fig. 1).
The patient survival rates at 1, 3, and 5 years were 91.7%, 55.6%, and 41.7%, respectively, in liver-free retransplantations, as compared with rates of 90.0%, 80.0%, and 80.0% in liver-inclusive retransplantations (P = 0.16). The graft survival rates at 1, 3, and 5 years were 76.2%, 40.6%, and 27.1%, respectively, in liver-free retransplantations as compared with rates of 90.0%, 80.0%, and 80.0% in liver-inclusive retransplantations. Therefore, the graft survival rates were higher in liver-inclusive retransplantations than in liver-free retransplantations (P = 0.03) (Fig. 2). There were no differences in patient or graft survivals between immediate and later retransplantation after enterectomy.
Immunologic Monitoring, Rejection Episodes and Outcomes After Retransplantation
Donor characteristics, recipient profile, and perioperative features are shown in Tables 2 and 3. Determination of specificities of preformed HLA antibodies was conducted in eight cases. Posttransplant antibody monitoring was performed in 10 cases, in which de novo DSA was detected in three. The average number of episodes of acute rejection (≥mild grade) experienced per patient during the first year was 1.77 (median, 2; range, 0–4), which was similar to that in primary transplants. The median onset of the first episode of acute rejection was 56 days (range, 4–203 days) after transplantation, and the majority of the first acute episodes occurred within the first three months. Of 13 recipients, three (23.1%) remained free of acute rejection, and two (15.4%) experienced only a single episode. However, eight (61.5%) lost grafts due to severe ACR (n = 3) or chronic rejection (n = 5) with a mean follow-up of 32.3 months (range, 8.4–84.7 months). Of these patients, six (46.2%) died secondary to rejection-related infections (n = 5) and TPN-related liver failure (n = 1).
In liver-inclusive retransplantations, the levels of both pretransplant PRA class I and PRA class II were significantly higher than those in liver-free retransplantations (P = 0.05). Determination of specificities of preformed HLA antibodies was conducted in nine cases. After transplantation, preformed DSA became undetectable in seven cases and persisted as positive in only one. In this group, the total number of episodes of mild ACR during the first year was significantly lower than that in liver-free retransplantations (P = 0.04). A single episode of moderate ACR but no severe ACR was observed in this group. The median onset of the first episode of ACR was delayed until 120 days (range, 14–201 days) after retransplantation, and the majority of the first acute episodes occurred after the first 3 months. With a mean follow-up of 44.5 months, five recipients (50%) experienced a single episode of mild ACR and 5 (50%) remained free of rejection. 2/10 (20.0%) succumbed to graft-versus-host disease (GVHD) (n = 1) and infection (n = 1).
After liver-inclusive retransplantations, a higher PRA level markedly decreased and remained low in most cases at the time of last follow-up. However, a PRA level slightly decreased after liver-free retransplantations (data not shown).
Current series of adult intestine retransplantation demonstrate that the long-term outcome was dismal in intestine retransplantations without a liver component, whereas simultaneous presence of a liver graft was associated with improved patient and graft survivals. Our results support that including the liver as part of an intestine graft at retransplantation may ameliorate or prevent intestine early and late graft rejection.
According to the Intestinal Transplant Registry data, the survival rate of retransplantation is only 20% in 2005 after 5 years.7 More recent single-center data have shown improved outcome of pediatric intestinal retransplantation, which has been attributed to advances in initial immunosuppression protocols, technical modifications, proper timing, and better infectious disease control.15 Our current study confirmed that graft and patient survival rates have significant improved in adult intestinal retransplantation over time.
The incidence of adult retransplantation at our single center is 10.2%, which is similar to the figures reported in the literature.6,16 The most common indication for retransplantation in this study was rejection, accounting for 87.5% of retransplanted patients. Mazariegos et al.15 reported that the majority of pediatric recipients who required retransplantations had previously undergone a liver-inclusive grafting. In contrast to pediatric recipients, the majority of adult patients underwent initial liver-free grafting.
Our results show that rejection is a primary cause of graft loss in an intestinal graft without a liver component. In these instances, a liver-free graft is associated with an increased acute rejection rate and occurrence of chronic rejection, possibly because of allosensitization because of blood transfusions, infections, previous transplantations, and so on. Our recent publication showed that in primary ITx, preformed DSA significantly increased the risk of acute rejection and persistent de novo DSA significantly increased the risk of chronic rejection.8 In this retrospective study, presence of DSA at retransplantation was also associated with rejection and graft loss. It is worthwhile to note that some patients did not have DSA at the time of graft loss, but DSA became detectable after enterectomy. It is possible that antibodies that are already present in serum are absorbed by the graft when it remains in place but becomes detectable in serum when the graft is removed. We also observed that in most cases, graft enterectomy was accompanied by sensitization, as evidenced by a rising PRA level. In addition, discontinuation of immunosuppression after enterectomy may contribute to sensitization. Early reports showed that in kidney transplantation, maintenance of low-dose immunosuppressive medication after graft nephrectomy before repeat transplantation appears to be effective in preventing sensitization.17-20 The impact of continuing low-dose immunosuppression as a means of preventing sensitization after enterectomy is currently unknown.
Our data demonstrate that patient and graft survival for liver-inclusive retransplantations are superior to liver-free retransplantations. This improved outcome is associated with a significant decrease in the rate and severity of ACR, which may help prevent the occurrence of chronic rejection. This finding supports the longstanding notion that the liver graft appears to protect the intestinal graft from antibody-mediated damage. Pretransplant PRA levels were markedly higher along with the presence of DSA, reflecting highly sensitized recipients in this group of patients. The exact causes of such higher sensitization in a liver-inclusive recipient are uncertain, but multiple transfusions, infections, and surgeries could be important contributing factors. After transplantation, PRA levels gradually decreased and preformed DSA became undetectable in most cases within 1 year. The exact mechanism for this immunoprotective effect is not well known but several potential mechanisms have been hypothesized. It has been speculated that this effect is secondary to the secretion of soluble HLA antigens by the liver to inhibit DSA and to phagocytosis of these reactive antibodies by Kupffer cells.21
In our liver-inclusive retransplantations, all recipients underwent splenectomy at the time of retransplantation or primary transplantation. In our practice, we did not transplant the donor spleen as part of the intestinal graft due to potential risk of GVHD. The removal of the spleen may contribute to the decrease of de novo DSA production and reduced acute rejection rate, which may therefore prevent the occurrence of chronic rejection in this group of patients.22,23 However, the combination of absence of the spleen and use of immunosuppressive agents might make recipients’ immune system oversuppressed and possibly result in a higher risk of infection and GVHD.24 The challenge for optimal management of this group of patients is to find a balance between overimmunosuppression and underimmunosuppression.
As in other forms of solid-organ transplantation, the presence of DSA has been implicated to both increase the incidence and severity of intestinal allograft rejection and worsen the overall prognosis for graft and patient. It is to be expected that DSA is more problematic for intestine retransplantations. Liver-inclusive retransplantations were associated with significant clearance of preformed DSA and lowered development of de novo DSA. As optimized strategies for removing DSA have not yet been established in ITx, the use of liver-inclusive grafts should be considered in highly sensitized recipients when retransplantation is necessary.
Some of the limitations of this study are its retrospective nature, the relative small cohort sizes, and the variability in technologies applied to detect HLA antibodies. Because of the unavailability of DSA detection methods before August 2003, a significant number of patients were not checked for DSA before primary transplantation and before retransplantation.
We conclude from our data that liver-inclusive intestinal retransplantations are more favorable than liver-free retransplantations. Careful patient selection, determination of graft type, and monitoring and treatment of HLA antibodies in a standardized manner are paramount when considering intestinal retransplantation.
MATERIALS AND METHODS
Since May 2000, patients undergoing an SB transplantation at the University of Pittsburgh Medical Center routinely had CDC-XM testing. We conducted a retrospective electronic medical records review of patients who received an SB transplantation between May 2000 and May 2010. The clinical charts were reviewed as needed for additional data. We investigated the incidence, indications, immunologic characteristics, transplant graft type, and short-term and long-term outcomes (n = 24). One recipient was excluded due to early death secondary to graft thrombosis, yielding 23 cases in the final analysis. Approval for data collection for this study was granted by the institutional review board.
Immunologic testing was performed as described previously.8 In brief, a CDC-XM was performed using T and B cells by antihuman globulin–enhanced or extended incubation or modified Amos technique. Human leukocyte antigen PRA screenings were performed using CDC (T and B cell plates) and enzyme-linked immunosorbent assay techniques. The specificities of HLA antibodies were determined by LAT Single Antigen enzyme-linked immunosorbent assay since November 2003 or Lab Screen Single Antigen Bead Luminex technique since September 2007. A positive CDC-XM did not preclude transplantation in our practice. Posttransplant DSA monitoring did not follow a standard protocol. The indication for DSA testing was usually higher PRA levels, refractory rejection, or suspicious of antibody-mediated rejection.
Transplant Graft Type
Donor and recipient operations have been previously described in detail.25,26 The transplant type consisted of an isolated intestine (SB), an MMV, including the stomach, duodenum, pancreas, and intestine, and a liver-inclusive full MV. The retransplanted recipients were divided into two groups: a liver-free (SB and MMV) and a liver-inclusive (MV) graft. The graft type at retransplantation was tailored to patient needs on the basis of organ function. The indications for liver-inclusive retransplantations were liver failure, as evidenced by a progressive rise in bilirubin, biopsy evidence of severe hepatic fibrosis, and portal hypertension. In liver-inclusive retransplantations, all 10 recipients underwent splenectomy (two at primary transplantation and eight at retransplantation).
At retransplantation, the use of immunosuppression had evolved during the study period. Ten patients (43.4%) did not receive induction therapy because of significant liver dysfunction or thrombocytopenia. Thirteen patients (58.3%) received a single dose of 5 mg/kg of rATG (Thymoglobulin; Genzyme, Cambridge, MA) (n = 3) or 30 mg of Alemtuzumab (Campath-1H; ILEX, Cambridge, MA) (n = 10). Two patients also received a low-dose (75 Gy) ex vivo irradiation and a single intravenous infusion of donor bone marrow cells 3 to 5 × 108 cell per kg per body weight. The maintenance immunosuppression was based on tacrolimus (Prograf; Astellas Pharma, Deefield, IL). A variable course of steroids was added in patients with a positive T/B CDC-XM. The 12-hr tacrolimus trough levels during the first 6 months were targeted at 10 to 15 ng/mL with induction therapy or 15 to 25 ng/mL without induction therapy. The process of weaning immunosuppression was only initiated 6 months after transplantation as described previously from our group. Immunosuppression was similar among recipients with liver-free retransplantations and liver-inclusive retransplantations.
All recipients with preformed DSA received a single dose of intravenous immunoglobulin at 2 gm/kg body weight on the day of transplantation. No patients received plasmapheresis or anti–B cell therapy before retransplantation.
Assessment of Rejection
Surveillance endoscopy was routinely performed twice per week for the first 2 to 3 weeks after transplantation and then weekly thereafter, with increased frequency if clinically indicated by increased stomal output, fever, abdominal pain, or other symptoms. The histologic criteria for diagnosis and determination of severity of ACR were as described previously.27 A diagnosis of acute humoral rejection was based on clinical evidence of graft dysfunction, pathologic evidence of tissue injury, and immunologic evidence of C4d deposition with circulating anti-HLA antibodies.28,29 A new rejection episode was defined by newly developed clinical symptoms and documentation of new histologic features of acute rejection with at least one normal mucosal biopsy between the rejection episodes. A diagnosis of chronic rejection was based on clinical presentations and was confirmed by a full-thickness specimen of partially or totally resected allografts to reveal evidence of vasculopathy and mesenteric lymphoid depletion with mesenteric sclerosis.30
The statistical analysis was performed by use of the MedCalc for Windows, version 126.96.36.199 (MedCalc Software, Mariakerke, Belgium). Data are presented as means ± standard deviation, unless otherwise stated. Categorical variables were analyzed with the use of the chi-square test or, when appropriate, Fisher exact test. Continuous variables were analyzed with the use of Student t test. Survival analysis was performed by the Kaplan-Meier method, compared by log-rank test. A P value equal or less than 0.05 was considered statistically significant.
The authors thank the surgical team and the nursing staff at the Intestinal Rehabilitation and Transplant Center, University of Pittsburgh Medical Center, for their excellent patient care. The authors also thank Mr. Yinglun Wu for his help in correcting the English.
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