Permanent detrimental effect of nonimmunological factors on long-term renal graft survival: a parsimonious model of time-dependency

Impact of Cold Ischemia Time in Kidney Transplants From Donation After Circulatory Death Donors

BACKGROUND

Deceased-donor kidneys are exposed to ischemic events from donor instability during the process of donation after circulatory death (DCD). Clinicians may be reluctant to transplant DCD kidneys with prolonged cold ischemia time (CIT) for fear of an additional deleterious effect.

METHODS

We performed a retrospective cohort study examining US registry data between 1998 and 2013 of adult first-time kidney-only recipients of paired kidneys (derived from the same donor transplanted into different recipients) from DCD donors.

RESULTS

On multivariable analysis, death-censored graft survival (DCGS) was comparable between recipients of kidneys with higher CIT relative to paired donor recipients with lower CIT when the CIT difference was 1 hour or longer (adjusted hazard ratio, [aHR], 1.02; 95% confidence interval [CI], 0.88-1.17; n = 6276), 5 hours or longer (aHR, 0.98; 95% CI, 0.80-1.19; n = 3130), 10 hours or longer (aHR, 1.15; 95% CI, 0.82-1.60; n = 1124) or 15 hours (aHR, 1.15; 95% CI, 0.66-1.99; n = 498). There was a higher rate of primary non function in the long CIT groups for delta 1 hour or longer (0.89% vs 1.63%; P = 0.006), 5 hours (1.09% vs 1.67%, P = 0.13); 10 hours (0.53% vs 1.78%; P = 0.03), and 15 hours (0.40% vs 1.61%; P = 0.18), respectively. Between each of the 4 delta CIT levels of shorter and longer CIT, there was a significantly and incrementally higher rate of delayed graft function in the long CIT groups for delta 1 hour or longer (37.3% vs 41.7%; P < 0.001), 5 hours (35.9% vs 42.7%; P < 0.001), 10 hours (29.4% vs 44.2%, P < 0.001), and 15 hours (29.6% vs 46.1%, P < 0.001), respectively. Overall patient survival was comparable with delta CITs of 1 hour or longer (aHR, 0.96; 95% CI, 0.84-1.08), 5 hours (aHR, 1.01; 95% CI, 0.85-1.20), and 15 hours (aHR, 1.27; 95% CI, 0.79-2.06) but not 10 hours (aHR, 1.47; 95% CI, 1.09-1.98).

CONCLUSIONS

These results suggest that in the setting of a prior ischemic donor event, prolonged CIT has limited bearing on long-term outcomes.

Risk Balancing of Cold Ischemic Time against Night Shift Surgery Possibly Reduces Rates of Reoperation and Perioperative Graft Loss

Background. This retrospective cohort study evaluates the advantages of risk balancing between prolonged cold ischemic time (CIT) and late night surgery. Methods. 1262 deceased donor kidney transplantations were analyzed. Multivariable regression was used to determine odds ratios (ORs) for reoperation, graft loss, delayed graft function (DGF), and discharge on dialysis. CIT was categorized according to a forward stepwise pattern ≤1h/>1h, ≤2h/>2h, ≤3h/>3h,…, ≤nh/>nh. ORs for DGF were plotted against CIT and a nonlinear regression function with best R² was identified. First and second derivative were then implemented into the curvature formula k(x) = f′′(x)/(1 + f′(x)²)^3/2 to determine the point of highest CIT-mediated risk acceleration. Results. Surgery between 3 AM and 6 AM is an independent risk factor for reoperation and graft loss, whereas prolonged CIT is only relevant for DGF. CIT-mediated risk for DGF follows an exponential pattern f(x) = A · (1 + k · e^{(I · x)}) with a cut-off for the highest risk increment at 23.5 hours. Conclusions. The risk of surgery at 3 AM–6 AM outweighs prolonged CIT when confined within 23.5 hours as determined by a new mathematical approach to calculate turning points of nonlinear time related risks. CIT is only relevant for the endpoint of DGF but had no impact on discharge on dialysis, reoperation, or graft loss.

Chronic Renal Transplant Rejection and Possible Anti-Proliferative Drug Targets

The global prevalence of renal transplants is increasing with time, and renal transplantation is the only definite treatment for end-stage renal disease. We have limited the acute and late acute rejection of kidney allografts, but the long-term survival of renal tissues still remains a difficult and unanswered question as most of the renal transplants undergo failure within a decade of their transplantation. Among various histopathological changes that signify chronic allograft nephropathy (CAN), tubular atrophy, fibrous thickening of the arteries, fibrosis of the kidney interstitium, and glomerulosclerosis are the most important. Moreover, these structural changes are followed by a decline in the kidney function as well. The underlying mechanism that triggers the long-term rejection of renal transplants involves both humoral and cell-mediated immunity. T cells, with their related cytokines, cause tissue damage. In addition, CD 20+ B cells and their antibodies play an important role in the long-term graft rejection. Other risk factors that predispose a recipient to long-term graft rejection include HLA-mismatching, acute episodes of graft rejection, mismatch in donor-recipient age, and smoking. The purpose of this review article is the analyze current literature and find different anti-proliferative agents that can suppress the immune system and can thus contribute to the long-term survival of renal transplants. The findings of this review paper can be helpful in understanding the long-term survival of renal transplants and various ways to improve it.

RGS4, a GTPase activator, improves renal function in ischemia-reperfusion injury

Acute kidney dysfunction after ischemia-reperfusion injury (IRI) may be a consequence of persistent intrarenal vasoconstriction. Regulators of G-protein signaling (RGSs) are GTPase activators of heterotrimeric G proteins that can regulate vascular tone. RGS4 is expressed in vascular smooth muscle cells in the kidney; however, its protein levels are low in many tissues due to N-end rule-mediated polyubiquitination and proteasomal degradation. Here, we define the role of RGS4 using a mouse model of IRI comparing wild-type (WT) with RGS4-knockout mice. These knockout mice were highly sensitized to the development of renal dysfunction following injury exhibiting reduced renal blood flow as measured by laser-Doppler flowmetry. The kidneys from knockout mice had increased renal vasoconstriction in response to endothelin-1 infusion ex vivo. The intrinsic renal activity of RGS4 was measured following syngeneic kidney transplantation, a model of cold renal IRI. The kidneys transplanted between knockout and WT mice had significantly reduced reperfusion blood flow and increased renal cell death. WT mice administered MG-132 (a proteasomal inhibitor of the N-end rule pathway) resulted in increased renal RGS4 protein and in an inhibition of renal dysfunction after IRI in WT but not in knockout mice. Thus, RGS4 antagonizes the development of renal dysfunction in response to IRI.

Vertical modeling: a pattern mixture approach for competing risks modeling

We study an alternative approach for estimation in the competing risks framework, called vertical modeling. It is motivated by a decomposition of the joint distribution of time and cause of failure. The two elements of this decomposition are (1) the time of failure and (2) the cause of failure condition on time of failure. Both elements of the model are based on observable quantities, namely the total hazard and the relative cause-specific hazards. The model can be implemented using the standard software. The relative cause-specific hazards are flexibly estimated using multinomial logistic regression and smoothing splines. We show estimates of cumulative incidences from vertical modeling to be more efficient statistically than those obtained from the standard nonparametric model. We illustrate our methods using data of 8966 leukemia patients from the European Group for Blood and Marrow Transplantation.

A pair analysis of the delayed graft function in kidney recipient: the critical role of the donor

PURPOSE

The aim of this study was to analyze the importance of donor factors and especially the potential role of hemodynamic management in regard to delayed graft function in paired kidney recipient patients after renal transplantation and to analyze the urine of organ donors by proton-nuclear magnetic resonance spectroscopy to identify urine markers potentially correlated with delayed graft function in recipient patients.

METHODS

A prospective multicenter epidemiologic study was conducted. A logistic regression model taking into account paired data was used.

RESULTS

Data from 72 donors and the 144 corresponding paired recipients were analyzed. Univariate analysis showed that age of donor, previous history of tobacco, ischemic cause of brain death, norepinephrine infusion, and recipient age were the risk factors for delayed graft function. After adjusting for correlated outcome data and controlling for other potential prognostic factors, 3 variables remained significantly associated with outcome: donor age (odds ratio [OR], 10.7), hemodynamic status (OR, 0.167), and hydroxyl-ethyl starch infusion (OR, 0.135). Proton-nuclear magnetic resonance analysis evidenced 3 metabolites of interest in donors (trimethylamine-N-oxide, citrate, and lactate). However, these peaks were not correlated the clinical parameters in donors.

CONCLUSIONS

Paired analysis of kidney transplantation emphasizes the important role of factor donor associated with delayed graft function in recipient. Thus, a particular attention should be paid to the hemodynamic management of donor.

Donor Dopamine Pretreatment Inhibits Tubulitis in Renal Allografts Subjected to Prolonged Cold Preservation

BACKGROUND

In the present study, we used the Brown-Norway (BN) to Lewis model as a model for acute rejection, to test the hypothesis that dopamine (DA) treatment of BN donors significantly reduces the inflammatory response after renal transplantation.

METHODS

BN and Lewis rats (isograft controls) were treated for 24 hr with DA (5 microg/kg/min) or NaCl (0.9%), respectively. After 24 hr of cold storage in University of Wisconsin (UW) solution, renal allografts were orthotopically transplanted into Lewis recipients. All recipients received immunosuppression until they were sacrificed. Allografts were harvested one, three, five, and 10 days after transplantation and analyzed by light microscopy, immunohistochemistry (CD3, major histocompatibility complex [MHC] class II, ED1, P-selectin and intercellular adhesion molecule [ICAM]-1) and by RNase protection assay for cytokine mRNA.

RESULTS

Ten days after transplantation Banff tubulitis scores were significantly lower in DA-treated than in NaCl-treated allografts. No significant differences were found in Banff interstitial infiltration scores. The numbers of MHC class II+ and CD3+ cells were significantly decreased in DA-treated animals as assessed by immunohistochemistry. No differences were found in the number of ED1+, P-selectin+, and ICAM-1+ cells. The expression of Ltalpha, tumor necrosis factor, interleukin-1beta, and interleukin-2 mRNA was significantly reduced in DA-treated animals.

CONCLUSION

Our data indicate that donor DA treatment significantly inhibits tubulitis in renal allografts subjected to prolonged cold preservation. A reduced number of infiltrating MHC class II+ and CD3+ cells together with decreased cytokine expression could diminish renal scarring, reduce allograft immunogenicity, and hence improve transplantation outcome.

Living donor renal transplantation: recent developments and perspectives

Renal transplantation is the optimal treatment for patients of all ages with end-stage renal disease. Life expectancy of the population in general is increasing consistently, as is the age of the dialysis population. Consequently, the average ages of kidney donors and recipients are rising. The combination of a growing number of patients with end-stage renal disease and a shortage of organs poses a significant challenge to the transplant community. Donor shortage is associated with unfavorable consequences (e.g. prolonged waiting time, and compromised graft and patient survival). As such, multidirectional efforts are required to expand the donor pool. Increasing the frequency of living donation seems to be an efficient solution. Living donation is associated with superior results for the recipient, and relatively benign long-term outcomes for donors. Reluctance to use organs from living donors whose eligibility was previously considered marginal (e.g. elderly donors) is declining. Although increased donor age is associated with reduced graft survival rates, this should not preclude use of older living donors; transplantation is definitely superior to remaining on dialysis. Thorough, standardized evaluation and careful screening for premorbid conditions in both elderly donors and elderly recipients are essential. Here, we present various options for expanding the living donor pool, with emphasis on the utilization of elderly living donors and transplantation in elderly recipients.

Chronologically different impacts of immunologic and non-immunologic risk factors on renal allograft function

INTRODUCTION

Upon analysis of the risk factors affecting renal graft survival and function, the time-dependent effects of each risk factor should be differentiated from their net effects. To evaluate the chronologically different impacts of risk factors on graft renal function, we reviewed 390 recipients who received a kidney from 1-haplotype-matched living-related donors.

MATERIALS AND METHODS

Until 5-yr post-transplantation (TX), yearly serum creatinine (Scr), 24-h urinary excretion of protein, and their yearly changes were compared by the episodes of acute rejection within 1 yr, the kidney weight to recipient body weight (KW/BW) ratio, the donor/recipient (D/R) age ratio, and the D/R gender pairing. The Kaplan-Meier method, Cox proportional hazard model, ANOVA, and repeated measures ANOVA were each applied for different purposes.

RESULTS

Only the episodes of acute rejection were a significant risk factor affecting graft survival. The episodes of acute rejection, KW/BW ratio, D/R age ratio, and D/R gender pairing consistently and independently had significant influences on Scr. Recipients having the lowest KW/BW ratio (first quartile) or the highest D/R age ratio (fourth quartile) had rapid increments of Scr after 4-yr post-TX. After 3-yr post-TX, there were significant correlations between the number of non-immunologic risk factors present and the yearly changes in Scr.

CONCLUSIONS

Non-immunologic factors had a detrimental effect on renal graft function, especially after 3-yr post-TX. If immunologic risks seem to be similar, size matching, age, and gender pairing should be considered for better long-term graft function in renal TX recipients.

Effect of donor age on the outcome of living-related kidney transplantation

The study compared the results of kidney transplantation from living-related donors older and younger than 60 years. The 273 kidney graft recipients were divided into group 1 (115 recipients of older grafts) and group 2 (158 recipients of younger grafts). The frequency of acute rejection (AR) episodes was similar in both groups but slow graft function occurred more frequently in group 1. The frequency of chronic renal allograft dysfunction in the first post-transplant year was significantly higher in group 1 than in group 2. Patient and graft survival was significantly worse in group 1. Risk factors for graft loss were the difference between donor and recipient age and AR. Donor age and graft function were risk factors for patient death. Although kidneys from older donors provide a statistically poorer transplant outcome, they are clinically acceptable, especially when waiting time is prolonged and access to dialysis limited.

Chronic renal allograft rejection: Pathophysiologic considerations

Chronic rejection is currently the most prevalent cause of renal transplant failure. Clinically, chronic rejection presents by chronic transplant dysfunction, characterized by a slow loss of function, often in combination with proteinuria and hypertension. The histopathology is not specific in most cases but transplant glomerulopathy and multilayering of the peritubular capillaries are highly characteristic. Several risk factors have been identified such as young recipient age, black race, presensitization, histoincompatability, and acute rejection episodes, especially vascular rejection episodes and rejections that occur late after transplantation. Chronic rejection develops in grafts that undergo intermittent or persistent damage from cellular and humoral responses resulting from indirect recognition of alloantigens. Progression factors such as advanced donor age, renal dysfunction, hypertension, proteinuria, hyperlipidemia, and smoking accelerate deterioration of renal function. At the tissue level, senescence conditioned by ischemia/reperfusion (I/R) may contribute to the development of chronic allograft nephropathy (CAN). The most effective option to prevent renal failure from chronic rejection is to avoid graft injury from both immune and nonimmune mechanism together with nonnephrotoxic maintenance immunosuppression.

Expanding the donor pool to increase renal transplantation

INTRODUCTION

The goal of the Eurotransplant renal allocation scheme is to provide every patient on the waiting list with a reasonably balanced opportunity for a donor offer. New initiatives were taken in order to maximize donor usage while maintaining a successful transplant outcome.

METHODS

Two Eurotransplant projects were launched in order to accommodate changes in donor and recipient profiles. A re-addressing of the non-heart-beating donor pool was undertaken and an allocation scheme in which organs from donors aged >65 are allocated to recipients aged >65 [the Eurotransplant Senior Programme (ESP)] was introduced.

RESULTS

Especially in The Netherlands, an enormous increase in the number of non-heart-beating donor kidneys has been observed, however with a pace-keeping reduction in heart-beating donors. The organization-wide implementation of the ESP has been successful. The 3 year graft survival rates for these age-matched transplants were as good as the human leukocyte antigen (HLA)-matched transplants (64 vs 67%) (P = 0.4).

CONCLUSION

Within the framework of sound research, the utmost flexibility and creativity is needed to keep or even increase the number of renal transplants when faced with a quantitatively stagnating but qualitatively deteriorating donor pool. Both the non-heart-beating donor protocol and the ESP have proven to be quite successful in achieving this goal without compromising the outcome for the individual end-stage renal disease patient.

Assessment of renal ischemia by optical spectroscopy1,2

INTRODUCTION

No reliable method currently exists for quantifying the degree of warm ischemia in kidney grafts before transplantation. We describe a method for evaluating pretransplant warm ischemia time using optical spectroscopic methods.

METHODS

Lewis rat kidney vascular pedicles were clamped unilaterally in vivo for 0, 5, 10, 20, 30, 60, 90, or 120 min; eight animals were studied at each time point. Injured and contralateral control kidneys were then flushed with Euro-Collins solution, resected, and placed on ice. 335 nm excitation autofluorescence as well as cross-polarized light scattering images were then taken of each injured and control kidney using filters of various wavelengths. The intensity ratio of the injured to normal kidneys was compared to ischemia time.

RESULTS

Autofluorescence intensity ratios through a 450-nm filter and light scattering intensity ratios through an 800-nm filter both decreased significantly with increasing ischemia time (P < 0.0001 for each method, one-way analysis of variance). All adjacent and nonadjacent time points between 0 and 90 min were distinguishable using one of these two modalities by Fisher's protected least significant difference.

CONCLUSIONS

Optical spectroscopic methods correlate with warm ischemia time in kidneys that have been subsequently hypothermically preserved. Further studies are needed to correlate results with physiological damage and posttransplant performance.

Metabolic syndrome is associated with impaired long-term renal allograft function; not all component criteria contribute equally

Chronic renal transplant dysfunction (CRTD) remains a leading cause of renal allograft loss. Evidence suggests that immunological and ischemic insults are mainly associated with CRTD occurring within the first year after transplantation, whereas nonimmunological insults are predominantly associated with CRTD beyond the first year. Several cardiovascular risk factors, such as obesity, dyslipidemia, hypertension, and diabetes mellitus have been identified as important nonimmunological risk factors for CRTD. These risk factors constitute the metabolic syndrome (MS). As renal allograft function is a surrogate marker of renal allograft loss, we investigated the association of MS with impairment of renal allograft function beyond the first year after transplantation in a cross-sectional study of 606 renal transplant outpatients. Metabolic syndrome was defined using the definition of the National Cholesterol Education Program. Renal allograft function was assessed as the 24-h urinary creatinine clearance. A total of 383 out of 606 patients (63%) suffered from MS at a median time of 6 years (2.6-11.4) post-transplant. Presence of MS was associated with impaired renal allograft function beyond 1 year post-transplant [-4.1 mL/min, 95%CI (-7.1, -1.1)]. The impact of MS did not change appreciably after adjustment for established risk factors for CRTD [-3.1 mL/min, 95%CI (-6.0, -0.2)]. However, not all component criteria of MS contributed equally. Only systolic blood pressure and hypertriglyceridemia were independently associated with impaired renal allograft function beyond 1 year post-transplant in multivariate analyses.

Predictors of lung transplant survival in eurotransplant

This study was undertaken to assess the influence of patient/donor and center factors on lung transplantation outcome. Outcomes of all consecutive first cadaveric lung transplants performed at 21 Eurotransplant centers in 1997-99 were analyzed. The risk-adjusted center effect on mortality was estimated. A Cox model was built including donor and recipient age and gender, primary disease, HLA mismatches, patient's residence, cold ischemic time, donor's cause of death, serum creatinine, type of lung transplant, respiratory support status, clinical condition and percentage predicted FEV1. The center effect was calculated (expressed as the standardized difference between the observed and expected survival rates), and empirical and full Bayes methods were applied to evaluate between-center differences. A total of 590 adults underwent lung transplantation. The primary disease (p=0.01), HLA-mismatches (p = 0.02), clinical condition(p < 0.0001) and the patient's respiratory support status (p = 0.05) were significantly associated with survival. After adjusting for case-mix, no between-center differences could be found. An in-depth empirical Bayes analysis showed the between-center variation to be zero. Similar results were obtained from the full Bayes analysis. Based on these data, there is no scientific basis to support a hypothesis of possible association between center volume and lung survival rates.

The superior results of living-donor renal transplantation are not completely caused by selection or short cold ischemia time: a single-center, multivariate analysis

BACKGROUND

The results of living-donor (LD) renal transplantations are better than those of postmortem-donor (PMD) transplantations. To investigate whether this can be explained by a more favorable patient selection procedure in the LD population, we performed a Cox proportional hazards analysis including variables with a known influence on graft survival.

METHODS

All patients who underwent transplantations between January 1981 and July 2000 were included in the analysis (n=1,124, 2.6% missing values). There were 243 LD transplantations (including 30 unrelated) and 881 PMD transplantations. The other variables included were the following: donor and recipient age and gender, recipient original disease, race, current smoking habit, cardiovascular disease, body weight, peak and current panel reactive antibody, number of preceding transplants and type and duration of renal replacement therapy, and time since failure of native kidneys. In addition, the number of human leukocyte antigen identical combinations, first and second warm and cold ischemia periods, left or right kidney and fossa, donor kidney anatomy, donor serum creatinine and proteinuria, and transplantation year were included.

RESULTS

In a multivariate model, donor origin (PMD vs. LD) significantly influenced the graft failure risk censored for death independently of any of the other risk factors (P=0.0303, relative risk=1.75). There was no time interaction. When the variable cold ischemia time was excluded in the same model, the significance of the influence of donor origin on the graft failure risk increased considerably, whereas the magnitude of the influence was comparable (P=0.0004, relative risk=1.92). The influence of all other variables on the graft failure risk was unaffected when the cold ischemia period was excluded. The exclusion of none of the other variables resulted in a comparable effect. Donor origin did not influence the death risk.

CONCLUSION

The superior results of LD versus PMD transplantations can be partly explained by the dichotomy in the cold ischemia period in these populations (selection). However, after adjustment for cold ischemia periods, the influence of donor origin still remained significant, independent of any of the variables introduced. This superiority is possibly caused by factors inherent to the transplanted organ itself, for example, the absence of brain death and cardiovascular instability of the donor before nephrectomy.

Chronic rejection with or without transplant vasculopathy

BACKGROUND

Chronic allograft nephropathy (CAN) is defined and graded in the Banff '97 scheme by the severity of interstitial fibrosis and tubular atrophy. It has been denoted that chronic rejection can be diagnosed if the typical vascular lesions are seen, consisting of fibrointimal thickening. We observed several patients who developed CAN without vascular changes or signs of cyclosporine toxicity. Therefore, we assessed the risk factor profiles of CAN with and without transplant vasculopathy.

METHODS

A cohort of 654 cadaveric renal transplants performed between 1983 and 1997 that functioned for more than 6 months was studied. Fifty-four transplants had CAN defined by a significant decline in renal function together with interstitial fibrosis and tubular atrophy without signs of cyclosporine nephrotoxicity or recurrent disease. Using the Banff chronic vascular (CV) score, 23 of 54 cases (43%) had a chronic vasculopathy score of 0 or 1 whereas 31 cases (57%) had a CV score of 2 or 3. Applying multivariate logistic regression, predictor variables of the two groups were compared with 231 transplants with a stable function for at least 5 yr.

RESULTS

Graft histology was obtained at a mean of 2.4 and 2.9 yr after transplantation in the group with or without vasculopathy, respectively. Acute rejection episodes (AREs) after 3 months post-transplantation were the strongest risk factor for both forms of CAN, odds ratio (OR) 14.7 (6.0-36.0). CAN with vasculopathy was also associated with transplants performed in the 1980s, OR 4.95 (1.65-14.9) and with creatinine clearance at 6 months, OR 0.58 (0.44-0.75) per 10 mL/min increase. In contrast, young recipient age, OR 0.69 (0.47-0.99) per 10-yr increase, and the presence of panel reactive antibodies at the time of transplantation, OR 1.26 (1.08-1.47) per 10% increase, were independent risk factors for CAN without vasculopathy.

CONCLUSIONS

After exclusion of cyclosporine toxicity or recurrent disease CAN occurred without moderate or severe transplant vasculopathy in 43% of the cases. The correlation with young recipient age, sensitization and late ARE suggest an immune pathogenesis, consistent with chronic rejection.

Predicting kidney graft failure using time-dependent renal function covariates

Chronic rejection and recurrent disease are the major causes of late graft failure in renal transplantation. To assess outcome, most researchers use Cox proportional hazard analysis with time-fixed covariates. We developed a model adding time-dependent renal function covariates to improve the prediction of late graft failure. We studied 692 kidney transplants at the Leiden University Medical Center that had functioned for at least 6 months. Graft failure from chronic rejection or recurrent disease occurred in 106 patients. The reciprocal of last recorded serum creatinine (RC), the ratio of RC and RC at 6 months (RC6), and the time elapsed since last observation (TEL) were used as time-dependent covariates. Cadaveric donor transplantation, a lower RC, and a lower ratio of RC/RC6 were independently associated with graft failure. The impact of the last recorded RC was dependent on its value, TEL, and the time since transplantation. Validation of the model confirmed much higher failure predictions in those with subsequent graft failure compared with nonfailures. This study illustrates that the prediction of late graft failure could be improved significantly by using time-dependent renal function covariates.

Ischemia times and donor serum creatinine in relation to renal graft failure

BACKGROUND

The results of renal transplantation are dependent on many variables. To simplify the decision process related to a kidney offer, the authors wondered which variables had the most important influence on the graft failure risk.

METHODS

All transplant patients (n=1,124) between January 1981 and July 2000 were included in the analysis (2.6% had missing values). The variables included were donor and recipient age and gender, recipient original disease, race, donor origin, current smoking, cardiovascular disease, body weight, peak and current panel reactive antibody (PRA), number of preceding transplants, type and duration of renal replacement therapy, and time since failure of native kidneys. Also, human leukocyte antigen (HLA) identity or not, first and second warm and cold ischemia times, left or right kidney and fossa, donor kidney anatomy, donor serum creatinine and proteinuria, and transplantation year were included.

RESULTS

In a multivariate model, cold ischemia time and its time-dependent variable significantly influenced the graft failure risk censored for death (P<0.0001) independent of any of the other risk factors. The influence primarily affected the risk in the first week after transplantation; thereafter, it gradually disappeared during the first year after transplantation. Donor serum creatinine also significantly influenced the graft failure risk in a time-dependent manner (P<0.0001). The risk of a high donor serum creatinine is already enlarged in the immediate postoperative phase and increases thereafter; the curve is closely related to the degree of the elevation. The other variables with a significant influence on the graft failure rate were, in order of decreasing significance, recipient age, donor gender, donor age, HLA identity, transplantation year, preceding transplantations, donor origin, and peak PRA.

CONCLUSIONS

Donor serum creatinine and cold ischemia time are important time-dependent variables independently influencing the risk of graft failure censored for death. The best strategy for improving the results of cadaveric transplantations is to decrease the cold ischemia time and to allocate kidneys from donors with an elevated serum creatinine to low-risk recipients.

Positive remote crossmatch: impact on short-term and long-term outcome in cadaver renal transplantation

BACKGROUND

A positive crossmatch with a "current" recipient serum (drawn shortly before the proposed transplant) is a contraindication to renal transplantation because of the risk of hyperacute rejection. Conflicting data have been reported concerning the significance of a positive crossmatch with "remote" sera (obtained months or years earlier) when the current crossmatch is negative.

METHODS

Recipients of a first or second cadaver transplant between June 1988 and April 1994 were studied. All transplants were performed with a negative "current" crossmatch. Retrospective crossmatches using "remote" sera were performed for all sensitized recipients.

RESULTS

Recipients with a positive remote crossmatch (RXM) demonstrated a higher incidence of delayed graft function and of acute rejection and graft loss occurring in the first year posttransplant than did sensitized recipients with a negative RXM or unsensitized recipients. In multivariate analysis, only recipients with both a positive RXM and delayed graft function were at significantly higher risk for graft loss. Grafts surviving the first year demonstrated similar half-lives whether the RXM was positive or negative.

CONCLUSIONS

The positive RXM, possibly in conjunction with other factors leading to very early graft damage, is a significant predictor of unfavorable transplant outcome in first and second renal transplants. This effect is seen early in the transplant course, and there seems to be no impact on outcome after the first year. Newer immunosuppressive modalities may help to reduce the early negative impact.

Multivariate analysis of donor risk factors for graft survival in kidney transplantation

BACKGROUND

The results of the transplantation of marginal donor kidneys remain controversial. This study aimed to investigate the impact of donor risk factors as predictors of kidney-graft outcome.

METHODS

Allograft failure risk factors were studied in 7,209 cadaveric kidney-transplant recipients reporting to the Etablissement français des Greffes (EfG) from 1996 to 2000, of which 544 (7.6%) were from donors aged over 60. Both univariate and multivariate analysis were used to assess the effect of donor risk factors and were stratified according to recipient age.

RESULTS

Overall graft survival was 91.1% (95% confidence interval [CI] 90.5-91.8) at 1 year, 88.6% (95% CI 87.8-89.4) at 2 years, and 85.6% (95% CI 84.6-86.6) at 3 years posttransplant. Univariate analysis of risk factors showed a significant reduction of graft survival in recipients transplanted with kidneys coming from donors older than 60 years, donors with a history of hypertension, a cerebrovascular cause of death, and a preharvesting serum creatinine greater than 150 micromol/L. Multivariate analysis revealed significantly higher failure rate associated with cerebrovascular cause of death (RR=1.2, P=0.02), history of hypertension (RR=1.2, P=0.04), and elevated serum creatinine (RR=1.3, P=0.03), whereas donor age greater than 60 years was not found as an independent risk factor.

CONCLUSIONS

Our results suggest that cerebrovascular cause of death, history of hypertension, and elevated creatinine are significant independent donor risk factors for graft survival, whereas donor age is a statistically significant, but dependent, risk factor. This result is important for the design of allocation and transplantation strategies for kidneys procured in elderly donors.

Mortality rates after heart transplantation: how to compare center-specific outcome data?

BACKGROUND

Studies of outcome in cardiac transplantation have focused primarily on identifying patient- and donor-related factors associated with patient mortality. Less consideration has been given to the impact of the transplant center. This study was undertaken to assess variability in heart transplantation outcome in Eurotransplant centers to provide a framework for auditing.

METHODS AND RESULTS

In a 2-year period, 1,401 adult patients underwent heart transplantation in 45 centers. The 1-year patient survival rate was 76% (95% CI, 74%-78%) with a range of 0% to 100% at the center level. The risk-adjusted center effect on mortality was estimated by calculating a standardized difference between the observed number of deaths 1 year after transplantation and the expected number of deaths based on the case mix. By assessing within- and between-center variations with empirical Bayes (EB) methods, after adjustment for all registered prognostic factors, an improved estimate of the true center effect was obtained. Compared with the standard risk-adjusted center effect method, fewer outlying centers were identified with the EB method.

CONCLUSION

EB methods, because they are known to incorporate more information from the data, enable a more precise and realistic portrayal of heart transplant centers' performances, compared with other risk-adjusted center effect methods. In the context of auditing procedures, EB methods should preferably be used for the identification of centers that deviate significantly from quality standards.

Evaluation of the Eurotransplant Senior Program. The results of the first year

On 4 January 1999, the Eurotransplant Senior Program (ESP) was implemented within the Eurotransplant kidney allocation scheme.

PATIENTS AND METHODS

Kidneys obtained from donors aged over 65 years of age (65+) were allocated to a selected group of nonimmunized 65+ patients undergoing their first transplant. All transplants were performed locally to minimize cold-ischemic time. All transplants performed with kidneys from elderly donors that were allocated via ESP (ESP group) were compared to transplants performed with similar kidneys allocated via the standard renal allocation system (control group). Initial kidney function and 1-year graft outcome were assessed.

RESULTS

In 1999, 227 ESP and 102 control transplants were performed. The duration of cold-ischemic time was 12 and 19 h for the ESP and control groups, respectively. No rejection episodes occurred in 60% and 67% of the ESP patients and controls, respectively, while a direct kidney function was observed in 59% of ESP and 49% of control patients. The 1-year graft survival rates, censoring for graft losses due to deaths in patients with functioning grafts, were 86% and 79%, respectively.

CONCLUSION

An old-for-old renal allocation algorithm can be successful provided that risk factors, such as cold-ischemic time, are reduced.

Accumulation of crystal deposits in abdominal organs following perfusion with defrosted University of Wisconsin solutions

Previous studies reported on both visible and invisible particles in University of Wisconsin (UW) solutions. Those particles originated from components of the bags. In recent clinical observations we noticed macroscopically visible, indissoluble particles in UW bags reaching subzero temperatures during transportation of organs and preservation solutions. In an experimental model we examined whether those particles could be detected following perfusion of abdominal organs with established perfusion solutions. UW-, HTK- or physiological saline solutions reached -3 +/- 0.5 degrees C under conditions frequently applied during transportation. UW solutions demonstrated the accumulation of visible, indissoluble crystals and were subsequently used for the perfusion of abdominal organs in LEW rats. After perfusion with UW solutions stored at freezing temperatures, crystals were detected in all abdominal organs localized in and around vessels, bile ducts, glomeruli and in the interstitium of harvested livers, kidneys and pancreas. By spectroscopy, we were able to characterize crystals as adenosine. A 40-microm pore-size filter eliminated crystals from UW solutions. Crystals were absent in organs perfused with HTK- or saline solutions kept at subzero conditions. UW solutions can reach subzero temperatures under commonly used transportation conditions. Under these conditions, visible crystals accumulate and can be detected in abdominal organs of an experimental system.

The differences between late graft loss group and long-term graft survival group in renal transplantation

In renal transplantation, the long-term graft survival rate has not been improved. Until now, the differences between late graft loss and long-term graft survival have still not been estimated thoroughly. We have attempted to define clinical risk factors and parameters for late graft loss by comparing the differences in these two groups. Data from the Osaka University Database were assessed on 156 renal allografts during a 7-yr period. Thirty-six patients comprised the late graft loss group (patients in this group had graft function without need for dialysis for more than 3 yr post-transplantation, afterwards lost the allograft: 'loss group'). One hundred and twenty patients comprised the long-term graft survival group (patients in this group had graft function without need for dialysis until 31 December 1999: 'survival group'). Various immunological and non-immunological parameters were included in an univariate regression analysis. This analysis showed that donor age (P < 0.01), HLA mismatch number (P < 0.01) and a repeat of acute rejection (P < 0.01) were significant factors. Serum creatinine levels at 3 months (P = 0.01), proteinuria at 1 yr (P < 0.01) and antihypertensive treatment at 2 yr (P = 0.03) after transplantation were predictive of the risk of late graft loss. CsA trough concentration at 3-6 months (P < 0.05) and body mass index increase at 1 yr (P = 0.046) were elevated in the loss group. These results from a single centre suggest that immunological as well as non-immunological factors are associated with the pathogenesis of late graft loss.

Horseshoe kidney transplantation within the eurotransplant region: a case control study

BACKGROUND

The horseshoe kidney is the most common anatomic renal variation, with an incidence of 1 in 600 to 800. It represents a fusion anomaly, usually of the lower poles. Horseshoe kidneys can be transplanted en bloc or after division of the renal isthmus. However, the great variation in origin, number, and size of renal arteries and veins leads to some reluctance to use horseshoe kidneys for transplantation. The aim of this study is to assess the results of horseshoe kidney transplantation.

METHODS

All data concerning horseshoe kidney transplantations within the Eurotransplant region were collected and were divided into en bloc and split transplantations. A matched control group was defined, and the three groups were analyzed with respect to the occurrence of primary nonfunction, graft survival, patient survival, and finally posttransplant serum creatinine values.

RESULTS

From 1983 to 2000, 8 horseshoe kidneys were transplanted en bloc and 26 were split and transplanted into 47 recipients. The results of these transplantations were compared with 110 transplantations in the control group. No significant differences among the three groups could be found, either in the short- or long-term posttransplant results.

CONCLUSIONS

The results of horseshoe kidney transplantation, either en bloc or split, are equal to the posttransplant results of kidneys with a normal anatomy. Bearing in mind the shortage of donors, horseshoe kidneys should certainly be used for transplantation.

Prolonged cold preservation augments vascular injury independent of renal transplant immunogenicity and function

BACKGROUND

While prolonged cold ischemia has detrimental effects on graft survival, the mechanisms remain unclear. We tested whether or not cold preservation enhances intragraft inflammatory responses and vascular injury.

METHODS

Rat renal grafts were cold preserved in University of Wisconsin solution for 2, 4, 6, 12, 24, and 48 hours, and then transplanted into syngeneic recipients and harvested after 24 hours. Frozen sections were examined histologically and stained for vascular cellular adhesion molecule-1 (VCAM-1), platelet-endothelial cell adhesion molecule-1 (PECAM-1), major histocompatibility complex (MHC) class II, tissue factor, leukocyte function associated molecule-1 (LFA-1), very late antigen-4 (VLA-4), as well as for inflammatory cells.

RESULTS

Function did not differ between isografts preserved for shorter (2 to 6 hours) or longer times (12 to 24 hours). Neutrophil influx and that of LFA-1-positive cells showed similar increases in all groups. Compared with short preservation groups, the long preserved grafts had more VLA-4-positive ED-1+ monocytic infiltrates adjacent to vessels expressing VCAM-1 (P < or = 0.001). Increased preservation duration had no effect on infiltration with recipient ED-2+ macrophages, MHC class II-positive cells, or dendritic cells. Decreased color intensity and continuity of PECAM-1 staining indicated loss of endothelial integrity in grafts preserved for longer than six hours. Intensity in VCAM-1 staining increased progressively in grafts preserved for more than six hours and was localized predominantly on the endothelium of elastic vessels. Endothelial cells, vascular smooth muscle cells, and monocytes expressed increasingly more tissue factor in grafts preserved for more than six hours, revealing enhanced intragraft procoagulant capacity. Furthermore, grafts with preservation times of more than six hours developed more severe vascular endothelial injury and worse tubular necrosis scores (P < or = 0.001) compared with grafts with shorter preservation times.

CONCLUSIONS

Because of the prominent vascular injury, strategies for endothelial protection should be attempted in grafts with long preservation times in clinical renal transplantation.