Long-term outcome of kidney transplantation from expanded criteria donors: a single center experience

Renal transplantation with expanded criteria donors: the experience of one Portuguese center

BACKGROUND

The shortage of kidneys available for transplantation has led to enlarged criteria donors (ECD): namely, donors older than 60 years or aged between 50 and 59 years with 2 of the following characteristics-hypertension, predonation serum creatinine level higher than 1.5 mg/dL or cerebrovascular disease as the cause of death. The aim of this study was to analyze renal transplants using ECD compared with standard criteria donors (SCD) concerning the incidences of delayed graft function (DGF), acute rejection episodes (ARE), and patient and graft survivals.

MATERIALS AND METHODS

This retrospective study of 409 cadaveric renal transplants over the last 4 years identified ECD in contrast with SCD.

RESULTS

Of the transplants, 24.4% used ECD. The baseline characteristics of recipients of ECD versus SCD kidneys were similar, except for age and cold ischemia time. Comparing ECD and SCD, we observed an higher incidence of DGF (35% vs 18%), occurrence of ARE (34.4% vs 16.6%), average serum creatinine levels at 6 (1.87 vs 1.4 mg/dL), and 12 months (1.88 vs 1.43 mg/dL) as well as lower graft survival at 1 (82% vs 91%) and 3 years (75% vs 84%) after transplantation. Recipient survival at 1 year was not different. Multivariate analysis identified recipient age, cold ischemia time, ARE, and DGF as risk factors for graft failure.

CONCLUSIONS

Renal transplantation with grafts from ECD shows significantly worse outcomes with higher rates of DGF and ARE, worse graft function, and lower graft survival.

Expanded Criteria Donors: Process and Outcomes

Expanded criteria donor (ECD) kidneys are transplantable deceased donor (DD) kidneys for which the average patient, graft survival, and renal function are inferior when compared to standard criteria DD kidneys. Although the term ECD kidneys has been used since the early 1990s to describe kidneys with various characteristics associated with poorer outcomes, the concept has been formally implemented in U.S. organ allocation. A DD kidney is considered to be an ECD organ if the estimated adjusted risk of graft failure is > or = 70% (RR > or = 1.70) compared to DD kidneys with standard characteristics of transplant suitability. The donor characteristics that define an ECD kidney include age > or = 60 years, or age 50-59 years plus two of the following: cerebrovascular accident as the cause of death, preexisting hypertension, or terminal serum creatinine greater than 1.5 mg/dl. In the aggregate, recipients of ECD kidneys have improved survival compared to end-stage renal disease (ESRD) patients on the kidney transplant waiting list. Patient survival is 5% lower at 1 year and 8-12% lower at 3-5 years for ECD kidney recipients. Adjusted graft survival in ECD kidneys is 8% lower at 1 year and 15-20% lower at 3-5 years after transplantation compared to standard criteria donor kidneys. However, patients less than 40 years of age, African Americans, Asians for whom the median waiting time is less than 1350 days receive no survival benefit from ECD kidney transplantation. Informed choice by the potential recipient is a prominent feature of the allocation policy regarding ECD kidneys. Since there are recipient characteristics associated with no survival benefit following ECD transplantation, nephrologists who refer patients for kidney transplantation should be familiar with the combination of donor and recipient factors that are likely to yield detrimental results.

Sensitivity of expanded-criteria donor kidneys to cold ischaemia time

The United Network for Organ Sharing (UNOS), working in conjunction with organ procurement organizations and transplant programmes, has recently defined a class of cadaver kidney grafts for special allocation procedures to enhance utilization of those organs. The criteria defining these expanded-criteria donor (ECD) kidneys are donor age > or = 60 yr or donor age between 50 and 59 yr plus two of the following characteristics: donor history of cerebrovascular accident (CVA), donor history of hypertension (htn), and elevated creatinine (>1.5) at any time during donor management. Kidney grafts from ECD donors carry an increased relative risk of non-function compared to other cadaver kidney grafts. The goal of the special allocation procedure is to reduce the time associated with placement by matching ECD grafts with patients previously designated as being willing to accept them. In assessing the potential impact of these allocation procedures, the sensitivity of ECD grafts to cold ischaemia time (CIT) became of great significance. Specifically, we questioned whether minimization of CIT might reduce the relative risk of poor graft function, justifying reduction of the geographical range of placement and thereby reducing the time the grafts would spend in-transit.

METHODS

To assess this, we queried the SEOPF database for cadaveric kidney transplants between 1/1/1997 and 15/8/2002. There were 1312 transplants from ECD donors during this period and 8451 from non-ECD donors. Between these groups, there were no significant differences in recipient gender, ethnicity, peak and most recent panel reactive antibody (PRA). Recipients of ECD kidneys were significantly older: 50.9 +/- 13.0 yr vs. 44.9 +/- 13.9 (mean age +/- SD, P < 0.0001). There were statistically significant but very small differences in the degree of AB and DR mismatch between the groups.

RESULTS

Defining delayed graft function (DGF) as dialysis within the first week post-transplant and primary non-function (PNF) as dialysis within the first week and failure in the first year, we found an association with CIT as illustrated in Table 1. Overall, ECD kidneys had a significantly increased (P < 0.0001) incidence of PNF and DGF. Notably, PNF in ECD appeared to be uniformly distributed across CIT and while DGF was CIT-dependent, the DGF differences between ECD and non-ECD were fairly consistent across CIT.

CONCLUSION

While CIT minimization is potentially beneficial, ECD kidneys do not appear to be more sensitive to it than non-ECD kidneys.

Prognostic significance of microvascular thrombosis in donor kidney allograft biopsies

BACKGROUND

With a continuing demand for donor kidneys for organ transplantation, it is important to understand the significance of pathologic findings in the donor organ before transplantation. Microvascular thrombosis is sometimes encountered in association with disseminated intravascular coagulation in the donor, and it is unclear whether this finding may affect immediate allograft function and long-term graft survival. To further elucidate this question, we examined our experience with microvascular thrombosis in donor biopsies in the kidney transplant program at our institution.

METHODS

Donor kidney biopsies showing microvascular thrombosis were identified from consecutive donor biopsies in the Duke University Medical Center transplant file database between January 1, 1995 and December 31, 2000. These biopsies and all other kidney biopsies and specimens from the recipients of these kidneys thus identified were reviewed. Sections were stained using a variety of methods, including hematoxylin-eosin, periodic acid-Schiff, methenamine silver, and Masson trichrome methods. Clinical records of the transplant recipients of these kidneys were also reviewed to assess allograft performance and survival.

RESULTS

From 230 consecutive donor kidney biopsies, we identified eight cases exhibiting donor-microvascular thrombosis. Mean follow-up times were 27.5 months for the thrombi group and 35 months for the non-thrombi group. Recipients of grafts with donor thrombi were more likely to exhibit delayed graft function, but graft function at 1 and 2 years and graft survival were similar between the two groups. Subsequent posttransplantation biopsies in five of eight cases showed no evidence of residual thrombosis.

CONCLUSIONS

These data suggest that the presence of donor microvascular thrombosis does not portend poor outcome in renal transplantation.

Severe arteriolar lesion mimicking drug-induced arteriolopathy in a long-term surviving renal allograft

We report severe arteriolar lesion mimicking drug-induced arteriolopathy in a renal allograft of a 37-year-old Japanese male, who has been treated by conventional immunosuppressive therapy but not administered cyclosporin or tacrolimus for 16 years after renal transplantation. Renal biopsy also showed glomerular changes including transplant glomerulopathy and features of chronic vascular rejection. The cause of the arteriolar lesion remains uncertain. Although its pathogenesis may be multi-factorial, long-term usage of conventional immunosuppressive agents and/or vascular rejection may contribute to the occurrence of the arteriolar lesion. We propose that biopsy study is needed for further understanding of histopathological behaviours of renal grafts in long-term survivors.

The use of expanded criteria cadaver and live donor kidneys for transplantation

The use of expanded criteria donors (non-traditional donors) can help lessen the current shortage of kidneys available for transplantation. The use of older donors has accounted for a large measure of the increase in the organ donation rate; however, the most significant factors found to impact on transplant success negatively traditionally have been shown to be extremes of donor age and last-hour urine output. Less significant variables affecting success rates are average systolic blood pressure, terminal serum creatinine, and days of hospitalization. With the appropriate selection of organs from expanded donors, acceptable outcomes can be obtained. When living donors are selected properly, kidneys with anatomic variants without pathologic significance can be used safely. Kidneys with a heightened potential for the development of progressive disease should not be transplanted. Efforts to decrease the cold ischemia time by increasing the use of kidneys from expanded criteria donors may improve the outcome of transplantation further. Advances in surgical techniques, preservation solutions, and methods for predicting eventual long-term renal function in kidneys from expanded donors will be critical in allowing precise selection criteria for kidneys for transplantation, resulting in the optimum use of a scarce and precious resource. Until options such as xenotransplantation become clinically feasible, the challenge will be to identify which donor organs previously considered suboptimal can be used safely to expand the organ donor pool.

Super long-term surviving two renal grafts with severe arteriolosclerosis and glomerulosclerosis

Two long-term renal transplant survivors, for about 20 yr, with unusual histological features in the allograft kidney are reported. In both cases, marked hyalinosis was observed in the arterioles of the transplanted kidney, despite never having been administered cyclosporine or tacrolimus. The cause remains unknown at the present time, but we think that the changes could be multifactorial in origin, including due to aging of the graft, hypertension, hyperlipidemia and chronic rejection. We conclude that histological analysis of the allograft kidney must be performed in long-term renal transplant survivors, in order to understand the histological changes in the chronic phase after kidney transplantation and to predict the prognosis of the graft.

Survival in recipients of marginal cadaveric donor kidneys compared with other recipients and wait-listed transplant candidates

An increasing number of cadaveric kidney transplants are now performed with organs from donors who would have been deemed unsuitable in earlier times. Although good allograft outcomes have been obtained with these marginal donor transplants, it is unclear whether recipients of marginal kidney transplants achieve a reduction in long-term mortality as do recipients of "ideal" kidneys. Patients with end-stage renal disease registered on the cadaveric renal transplant waiting list between January 1, 1992, and June 30, 1997, were studied for mortality risks according to three outcomes: wait-listed on dialysis treatment with no transplant (WLD); transplantation with marginal donor kidney (MDK); and "ideal" or optimal donor kidney transplantation (IDK). Thirty-four percent of wait-list registrants had received a cadaveric kidney transplant by June 30, 1998. Of these, 18% received a marginal kidney that had one or more of the following pretransplant factors: donor age >55 yr, non-heartbeating donor, cold ischemia time >36 h, and donor hypertension or diabetes mellitus of > 10 yr duration. Five-year graft and patient survival was 53% and 74% for MDK recipients compared with 67% (P< 0.001) and 80% (P< 0.001) for IDK recipients. Adjusted annual death rate and estimated remaining life time was 6.3%, 4.7%, and 3.3% and 15.3 yr, 20.4 yr, and 28.7 yr for WLD, MDK, and IDK groups, respectively. The average increase in life expectancy for MDK recipients compared with the WLD cohort was 5 yr, although this benefit varied from 3 to 10 yr depending on the recipient's characteristics. It is concluded that transplantation of a marginal kidney is associated with a significant survival benefit when compared with maintenance dialysis.