Impact of cold ischemia time on the outcomes of kidneys with Kidney Donor Profile Index ≥85%: mate kidney analysis - a retrospective study

Interaction between cold ischemia time and Kidney Donor Profile Index on postrenal transplant outcomes

We analyzed whether there is an interaction between the Kidney Donor Profile Index (KDPI) and cold ischemia time (CIT) in recipients of deceased donor kidney transplant (KTs). Adults who underwent KTs in the United States between 2014 and 2020 were included and divided into 3 KDPI groups (≤20%, 21%-85%, >85%) and 4 CIT strata (<12, 12-17.9, 18-23.9, ≥24 hours). Multivariate analyses were used to test the interaction between KDPI and CIT for the following outcomes: primary graft nonfunction (PGNF), delayed graft function (DGF), estimated glomerular filtration rate (eGFR) at 6 and 12 months, patient survival, graft survival, and death-censored graft survival (DCGS). A total of 69,490 recipients were analyzed: 18,241 (26.3%) received a graft with KDPI ≤20%, 46,953 (67.6%) with KDPI 21%-85%, and 4,296 (6.2%) with KDPI >85%. Increasing KDPI and CIT were associated with worse post-KT outcomes. Contrary to our hypothesis, howerver, the interaction between KDPI and CIT was statistically significant only for PGNF and DGF and eGFR at 6 months. Paradoxically, the negative coefficient of the interaction suggested that increasing duration of CIT was more detrimental for low and intermediate-KDPI organs relative to high-KDPI grafts. Conversely, for mortality, graft survival, and DCGS, we found that the interaction between CIT and KDPI was not statistically significant. We conclude that, high KDPI and prolonged CIT are independent risk factors for inferior outcomes after KT. Their interaction, however, is statistically significant only for the short-term outcomes and more pronounced on low and intermediate-KDPI grafts than high-KDPI kidneys.

Preventing Rejection of the Kidney Transplant

With increasing knowledge of immunologic factors and with the advent of potent immunosuppressive agents, the last several decades have seen significantly improved kidney allograft survival. However, despite overall improved short to medium-term allograft survival, long-term allograft outcomes remain unsatisfactory. A large body of literature implicates acute and chronic rejection as independent risk factors for graft loss. In this article, we review measures taken at various stages in the kidney transplant process to minimize the risk of rejection. In the pre-transplant phase, it is imperative to minimize the risk of sensitization, aim for better HLA matching including eplet matching and use desensitization in carefully selected high-risk patients. The peri-transplant phase involves strategies to minimize cold ischemia times, individualize induction immunosuppression and make all efforts for better HLA matching. In the post-transplant phase, the focus should move towards individualizing maintenance immunosuppression and using innovative strategies to increase compliance. Acute rejection episodes are risk factors for significant graft injury and development of chronic rejection thus one should strive for early detection and aggressive treatment. Monitoring for DSA development, especially in high-risk populations, should be made part of transplant follow-up protocols. A host of new biomarkers are now commercially available, and these should be used for early detection of rejection, immunosuppression modulation, prevention of unnecessary biopsies and monitoring response to rejection treatment. There is a strong push needed for the development of new drugs, especially for the management of chronic or resistant rejections, to prolong graft survival. Prevention of rejection is key for the longevity of kidney allografts. This requires a multipronged approach and significant effort on the part of the recipients and transplant centers.

Cold Ischemia Time, Kidney Donor Profile Index, and Kidney Transplant Outcomes: A Cohort Study

Rationale & Objective

An average of 3,280 recovered deceased donor kidneys are discarded annually in the United States. Increased cold ischemia time is associated with an increased rate of organ decline and subsequent discard. Here we examined the effect of prolonged cold ischemia time on kidney transplant outcomes.

Study Design

Retrospective observational study.

Setting & Participants

Recipients of deceased donor kidney transplants in the United States from 2000 to 2018.

Exposure

Recipients of deceased donor kidneys were divided based on documented cold ischemia time: ≤16, 16-24, 24-32, 32-40, and >40 hours.

Outcomes

The incidence of delayed graft function, primary nonfunction, and 10-year death-censored graft survival.

Analytical Approach

The Kaplan-Meier method was used to generate survival curves, and the log rank test was used to compare graft survival.

Results

The rate of observed delayed graft function increased with cold ischemia time (20.9%, 28.1%, 32.4%, 37.5%, and 35.8%). Primary nonfunction also showed a similar increase with cold ischemia time (0.6%, 0.9%, 1.3%, 2.1%, and 2.3%), During a median follow-up time of 4.6 years, 37,301 recipients experienced death-censored graft failure. Analysis based on kidney donor profile index (KDPI) demonstrated significant differences in 10-year death-censored graft survival, with a death-censored graft survival in recipients of a kidney with a KDPI <85% of 71.0% (95% CI, 70.5%-71.5%), 70.5% (95% CI, 69.9%-71.0%), 69.6% (95% CI, 68.7%-70.4%), 65.5% (95% CI, 63.7%-67.3%), and 67.2% (95% CI, 64.6%-69.6%), compared to 53.5% (95% CI, 51.1%-55.8%), 50.7% (95% CI, 48.3%-53.1%), 50.3% (95% CI, 46.6%-53.8%), 50.7% (95% CI, 45.1%-56.1%), and 48.3% (95% CI, 40.0%-56.1%), for recipients of a kidney with a KDPI >85%.

Limitations

Heterogeneity of acceptance patterns among transplant centers, presence of confounding variables leading to acceptance of kidneys with prolonged cold ischemia times.

Conclusions

Cold ischemia time was associated with an increased risk of delayed graft function and primary nonfunction. However, the effect of increased cold ischemia time is modest and has less impact than the KDPI. Transplant programs should not consider prolonged cold ischemia time alone as a predominant reason to decline an organ, especially with a KDPI <85%.

Donor Death Category Is an Effect Modifier Between Cold Ischemia Time and Post-transplant Graft Function in Deceased-Donor Kidney Transplant Recipients

Objectives: We aimed to analyze the effect of cold ischemia time (CIT) on post-transplant graft function through mixed-effect model analysis to reduce the bias caused by paired mate kidneys.

Methods: We reviewed all kidney transplantation records from 2015 to 2019 at our center. After applying the exclusion criteria, 561 cases were included for analysis. All donor characteristics, preservation and matching information, and recipient characteristics were collected. Transplant outcomes included delayed graft function (DGF) and estimated glomerular filtration rate (eGFR). Generalized linear mixed models were applied for analysis. We also explored potential effect modifiers, namely, donor death category, expanded criteria donors, and donor death causes.

Results: Among the 561 cases, 79 DGF recipients developed DGF, and 15 recipients who died after surgery were excluded from the eGFR estimation. The median stable eGFR of the 546 recipients was 60.39 (47.63, 76.97) ml/min/1.73 m². After adjusting for confounding covariates, CIT had a negative impact on DGF incidence [odds ratio = 1.149 (1.006, 1.313), P = 0.041]. In the evaluation of the impact on eGFR, the regression showed that CIT had no significant correlation with eGFR [β = −0.287 (−0.625, 0.051), P = 0.096]. When exploring potential effect modifiers, only the death category showed a significant interaction with CIT in the effect on eGFR (P_interaction = 0.027). In the donation after brain death (DBD) group, CIT had no significant effect on eGFR [β = 0.135 (−0.433, 0.702), P = 0.642]. In the donation after circulatory death/donation after brain death followed by circulatory death (DCD/DBCD) group, CIT had a significantly negative effect on eGFR [β= −0.700 (−1.196, −0.204), P = 0.006]. Compared to a CIT of 0–6 h, a CIT of 6–8 or 8–12 h did not decrease the post-transplant eGFR. CIT over 12 h (12–16 h or over 16 h) significantly decreased eGFR. With the increase in CIT, the regenerated eGFR worsened (P_trend = 0.011).

Conclusion: Considering the effect of paired mate kidneys, the risk of DGF increased with prolonged CIT. The donor death category was an effect modifier between CIT and eGFR. Prolonged CIT did not reduce the eGFR level in recipients from DBDs but significantly decreased the eGFR in recipients from DCDs/DBCDs. This result indicates the potential biological interaction between CIT and donor death category.

Analysis of risk factors for donation after circulatory death kidney transplantation in Japan

Background

In Japan, donations after circulatory death kidney transplantation are widely performed due to legislation delays. The number of donations after brain death kidney transplantations is increasing, but the target remains unmet. We reviewed the outcomes of donation after circulatory death in Japan.

Methods

We analyzed 2923 deceased kidney transplantations (2239: donation after circulatory death (DCD), 684: donation after brain death (DBD)) performed in Japan from 2000 to 2019. The outcomes of the DCD and DBD groups were compared. We examined the risk factors for graft loss in the DCD group.

Results

The 5-year patient survival and death-censored graft survival rates of the DCD group, obtained by propensity score matching, were 93.6% and 95.2%, respectively, which were equivalent to 94.2% and 93.8%, respectively, obtained in the DBD group. Older donors (≥ 50 years) and prolonged cold ischemia time (≥ 12 h) were risk factors for graft loss; in the presence of these, graft survival was lower in the DCD group.

Conclusions

Older donors and prolonged cold ischemia time reduced graft survival in the DCD group. Proper evaluation of donors and careful preparation for transplant surgery are, therefore, essential to ensure good transplant outcomes.

Recipient Obesity and Kidney Transplant Outcomes: A Mate-Kidney Analysis

RATIONALE & OBJECTIVE

The impact of extreme recipient obesity on long-term kidney transplant outcomes has been controversial. This study sought to evaluate the association of various levels of recipient obesity on kidney transplantation outcomes by comparing mate-kidney recipient pairs to address possible confounding effects of donor characteristics on posttransplant outcomes.

STUDY DESIGN

Nationwide observational cohort study using mate-kidney models.

SETTING & PARTICIPANTS

In analysis based on the Organ Procurement and Transplant Network/United Network of Organ Sharing database, 44,560 adult recipients of first-time deceased-donor kidney transplants from 2001 through 2016 were paired by donor.

PREDICTORS

Recipient body mass index (BMI) categorized as 18-25 (n = 12,446), >25-30 (n = 15,477), >30-35 (n = 11,144; obese), and >35 (n = 5,493; extreme obesity) kg/m².

OUTCOMES

Outcomes included patient survival, graft survival, death-censored graft survival, delayed graft function (DGF), and hospital length of stay.

ANALYTICAL APPROACH

Conditional logistic regression and stratified proportional hazards models were used to compare outcomes as odds ratios and hazard ratios (HRs), adjusted for recipient and transplant factors, using recipients with a BMI >35 kg/m² as a reference.

RESULTS

At a median follow-up of 3.9 years, adjusted odds ratios for DGF were 0.42 (95% CI, 0.36-0.48), 0.55 (95% CI, 0.48-0.62), and 0.73 (95% CI, 0.64-0.83) for BMI 18-25, >25-30, and >30-35 kg/m², respectively (P < 0.001 for all). Death-censored graft failure was less frequent for BMI ≤25 and >25-30 kg/m² (HRs of 0.66 [95% CI, 0.59-0.74] and 0.79 [95% CI, 0.70-0.88], respectively; P < 0.001 for both), but not for BMI >30-35 kg/m² (HR, 0.91 [95% CI, 0.81-1.02]; P = 0.09). Length of stay and patient survival did not differ by recipient BMI.

LIMITATIONS

Observational study with limited detail regarding potential confounders.

CONCLUSIONS

Despite an increased risk of DGF likely unrelated to donor organ quality, long-term transplant outcomes among recipients with a BMI >35 kg/m² are similar to those among recipients with a BMI >30-35 kg/m², supporting a flexible approach to kidney transplantation candidacy in candidates with extreme obesity.

Marginal kidney transplantation: the road less traveled

PURPOSE OF REVIEW

Kidney transplantation indisputably confers a significant survival advantage and a better quality of life compared with dialysis, however, because of the increasing demand for kidney transplantation many patients continue to wait prolonged periods for kidney transplantation. The first step to alleviate the shortage is to reduce the discard rate by utilizing more marginal kidneys. This review studied the recent literature on marginal kidney transplantation.

RECENT FINDINGS

More than 60% of high-KDPI kidneys are discarded. Despite the increase in posttransplant costs, use of high KDPI transplants suggests a gain in survival years, thus making marginal kidney transplant cost effective. Furthermore, recent evidence suggests that marginal kidney transplantation shows a survival benefit compared with remaining in the waitlist and minimizes the kidney discard rate.

SUMMARY

Transplantation with marginal kidneys provides a survival benefit over dialysis or waiting for a low-KDPI kidney. As a result, clinicians should strongly consider transplantation of marginal kidneys as opposed to waiting for a better offer.

Expanded Criteria Donor Kidneys With Kidney Donor Profile Index ≤ 85%: Are We Doing Enough to Counsel Our Patients?

BACKGROUND

Kidneys at higher risk for allograft failure are defined by the Kidney Donor Profile Index (KDPI) > 85% in the current kidney allocation system (KAS), replacing the historical concept of expanded criteria donor (ECD) kidneys in the previous KAS. Discrepancies exist in the classification of "high-risk kidneys" between the 2 KAS. In the current KAS, only recipients of KDPI > 85% kidneys are counseled about the high risk of allograft failure and are required to sign a consent. In this study, we evaluated the outcomes and allocation of kidneys with discordant classification.

METHODS

Using the Scientific Registry of Transplant Recipients, kidneys transplanted between 01/2002 and 09/2016 were classified according to the old (standard criteria donor [SCD]/ECD) and current (KDPI) KAS. We then grouped them as concordant (KDPI ≤ 85% + SCD or KDPI > 85% + ECD) and discordant (KDPI ≤ 85% + ECD or KDPI > 85% + SCD) kidneys.

RESULTS

Approximately 11% of transplanted kidneys were discordant in classification. Among kidneys with KDPI ≤ 85%, ECD status conferred a 64% (95% CI: 56%-73%) higher risk of allograft failure compared to SCD status. However, SCD/ECD status was not associated with differential outcomes in KDPI > 85% kidneys. These ECD kidneys have KDPIs > 50% and have been transplanted across all estimated post-transplant survival (EPTS) deciles.

CONCLUSION

Adequate counseling about the risk and benefit of accepting ECD kidneys with KDPI ≤ 85% versus waiting on dialysis should be explored with the patients, especially those with lower EPTS.

Changes in double-strand DNA breaks predict delayed graft function (DGF) in Japanese renal allograft recipients

BACKGROUND

Although delayed graft function (DGF) is a serious complication following kidney transplantation, a reliable and early diagnostic test is lacking to identify the grade of DGF.

METHODS

We investigated changes in double-strand DNA breaks (DSBs), and factors related to DGF, such as ischemic times at transplantation and serum creatinine (sCr) levels. DSBs were detected by phospho-histone H2A.X (γ-H2AX) expression and cellular regeneration by Ki-67 before (0 h) and 1 h after allograft reperfusion (1 h) in each subject.

RESULTS

The expression of γ-H2AX or Ki-67 at 0 h showed no difference between the living and deceased donors. γ-H2AX at 1 h decreased in the living donors, but increased in the deceased donors compared with that of 0 h(p = 0.017). Changes (Δ) in γ-H2AX between 0 and 1 h were different among subgroups, i.e., immediate function, slow graft function with dialysis < 7 days, DGF with dialysis < 4 weeks, severe DGF with dialysis > 4 weeks, or primary non-function (PNF) (p = 0.04). Severe DGF and PNF cases showed greater increase in Δγ-H2AX (p = 0.019), and were distinguished by > 12% of Δγ-H2AX at 100% sensitivity and 88.2% specificity (ROC analysis, AUC: 0.922, p = 0.023). In a multivariate regression analysis, donor sCr and Δγ-H2AX were two main predictors of the grade of DGF (p = 0.002). The expression of Ki-67 was very low at both 0 h and 1 h.

CONCLUSION

The combination of donor sCr and Δγ-H2AX from 0 to 1 h after reperfusion may predict severe DGF and PNF in the early phase.

Immunologic Risk Assessment and Approach to Immunosuppression Regimen in Kidney Transplantation

The outcomes of kidney transplantation show a steady improvement with an increasing number of transplantations and decreasing incidence of acute rejection episodes. Successful transplantation begins with a comprehensive immunologic risk assessment and judicious choice of therapeutic agents. In this review, we discuss the trends in transplant immunosuppression practices and outcomes in the United States. We discuss practical testing algorithms for clinical decision making in induction therapy and fine-tuning maintenance immunosuppression. We introduce assessment tools for immune monitoring after transplantation and speculate on future directions in management.

Association of Kidney Transplant Center Volume With 3-Year Clinical Outcomes

RATIONALE & OBJECTIVE

A robust relationship between procedure volume and clinical outcomes has been demonstrated across many surgical fields. This study assessed whether a center volume-outcome relationship exists for contemporary kidney transplantation, specifically for diabetic recipients, older recipients (aged ≥65 years), and recipients of high kidney donor profile index (KDPI ≥ 85) kidneys.

STUDY DESIGN

Retrospective cohort study.

SETTING & PARTICIPANTS

Adult kidney-only transplant recipients who underwent transplantation between 2009 and 2013 (N = 79,581).

EXPOSURES

The primary exposure variable was center volume, categorized into quartiles based on the total kidney transplantation volume. Quartile 1 (Q1) centers performed a mean of fewer than 66 kidney transplantations per year, whereas Q4 centers performed a mean of more than 196 kidney transplantations per year.

OUTCOMES

All-cause graft failure and mortality within 3 years of transplantation.

ANALYTICAL APPROACH

Multivariable Cox frailty models were used to adjust for donor characteristics, recipient characteristics, and cold ischemia time.

RESULTS

Minor differences in rates of 3-year deceased donor all-cause graft failure across quartiles of center volume were observed (14.9% for Q1 vs 16.7% for Q4), including in subgroups (diabetic recipients, 18.4% for Q1 vs 19.7% for Q4; older recipients, 19.4% for Q1 vs 22.5% for Q4; recipients of high KDPI kidneys, 26.5% for Q1 vs 26.5% for Q4). Results were similar for 3-year mortality. After adjustment for donor, recipient, and graft characteristics using Cox regression, center volume was not significantly associated with all-cause graft failure or mortality within 3 years, except that diabetic recipients at Q3 centers had slightly lower mortality (compared with Q1 centers, adjusted HR of 0.85 [95% CI, 0.73-0.99]).

LIMITATIONS

Potential unmeasured confounding from patient comorbid conditions and organ selection.

CONCLUSIONS

These findings provide little evidence that care in higher volume centers is associated with better adjusted outcomes for kidney transplant recipients, even in populations anticipated to be at increased risk for graft failure or death.

Intra-operative Postperfusion Micronephrolithotomy for Renal Allograft Lithiasis: A Case Report

Increasing demand drives the expansion of criteria for kidney donation, and nephrolithiasis is now considered a relative contraindication. We report for the first time a case of intra-operative, postperfusion kidney allograft micronephrolithotomy. A 64-year-old man with end-stage renal disease secondary to Alport syndrome underwent primary deceased donor kidney transplantation at our center. Pre-operative ultrasound of the donor identified a 7-mm calculus in the anterior, lower pole calyx. The kidney was extra-peritoneally implanted in the right iliac fossa and reperfused homogenously. Stone retrieval with a flexible ureteroscope failed due to the narrow calyceal infundibulum. Instead, the calculus was removed using the micropercutaneous nephrolithotomy system under ultrasonographic guidance. The calyx was punctured using a 4.85 Fr needle and the stone was fragmented to dust using a Holmium laser. No bleeding was observed. The post-operative course was uneventful. Outpatient follow up demonstrated good function of the graft which was stone free on ultrasound. Postperfusion micropercutaneous nephrolithotomy for kidney allograft calculi offers a safe and feasible option when pre-operative or intra-operative retrograde intrarenal surgery fails.

Barriers and Advances in Kidney Preservation

Despite the fact that a significant fraction of kidney graft dysfunctions observed after transplantation is due to ischemia-reperfusion injuries, there is still no clear consensus regarding optimal kidney preservation strategy. This stems directly from the fact that as of yet, the mechanisms underlying ischemia-reperfusion injury are poorly defined, and the role of each preservation parameter is not clearly outlined. In the meantime, as donor demography changes, organ quality is decreasing which directly increases the rate of poor outcome. This situation has an impact on clinical guidelines and impedes their possible harmonization in the transplant community, which has to move towards changing organ preservation paradigms: new concepts must emerge and the definition of a new range of adapted preservation method is of paramount importance. This review presents existing barriers in transplantation (e.g., temperature adjustment and adequate protocol, interest for oxygen addition during preservation, and clear procedure for organ perfusion during machine preservation), discusses the development of novel strategies to overcome them, and exposes the importance of identifying reliable biomarkers to monitor graft quality and predict short and long-term outcomes. Finally, perspectives in therapeutic strategies will also be presented, such as those based on stem cells and their derivatives and innovative models on which they would need to be properly tested.

Kidney transplantation in older recipients: Preemptive high KDPI kidney vs lower KDPI kidney after varying dialysis vintage

AIM

To evaluate the outcomes of transplanting marginal kidneys preemptively compared to better-quality kidneys after varying dialysis vintage in older recipients.

METHODS

Using OPTN/United Network for Organ Sharing database from 2001-2015, we identified deceased donor kidney (DDK) transplant recipients > 60 years of age who either underwent preemptive transplantation of kidneys with kidney donor profile index (KDPI) ≥ 85% (marginal kidneys) or received kidneys with KDPI of 35%-84% (better quality kidneys that older wait-listed patients would likely receive if waited longer) after being on dialysis for either 1-4 or 4-8 years. Using a multivariate Cox model adjusting for donor, recipient and transplant related factors- overall and death-censored graft failure risks along with patient death risk of preemptive transplant recipients were compared to transplant recipients in the 1-4 and 4-8 year dialysis vintage groups.

RESUTLS

The median follow up for the whole group was 37 mo (interquartile range of 57 mo). A total of 6110 DDK transplant recipients above the age of 60 years identified during the study period were found to be eligible to be included in the analysis. Among these patients 350 received preemptive transplantation of kidneys with KDPI ≥ 85. The remaining patients underwent transplantation of better quality kidneys with KDPI 35-84% after being on maintenance dialysis for either 1-4 years (n = 3300) or 4-8 years (n = 2460). Adjusted overall graft failure risk and death-censored graft failure risk in preemptive high KDPI kidney recipients were similar when compared to group that received lower KDPI kidney after being on maintenance dialysis for either 1-4 years (HR 1.01, 95%CI: 0.90-1.14, P = 0.84 and HR 0.96, 95%CI: 0.79-1.16, P = 0.66 respectively) or 4-8 years (HR 0.82, 95%CI: 0.63-1.07, P = 0.15 and HR 0.81, 95%CI: 0.52-1.25, P = 0.33 respectively). Adjusted patient death risk in preemptive high KDPI kidney recipients were similar when compared to groups that received lower KDPI kidney after being on maintenance dialysis for 1-4 years (HR 0.99, 95%CI: 0.87-1.12, P = 0.89) but lower compared to patients who were on dialysis for 4-8 years (HR 0.74, 95%CI: 0.56-0.98, P = 0.037).

CONCLUSION

In summary, our study supports accepting a “marginal” quality high KDPI kidney preemptively in older wait-listed patients thus avoiding dialysis exposure.

Role of induction therapy in low immunological risk-kidney transplant recipients: A mate-kidney analysis

We aimed to evaluate the impact of induction on outcomes in low-immunological risk kidney transplant recipients (KTRs) using a mate-kidney model. Using OPTN/UNOS database, we identified three groups of low-immunological risk KTRs (first transplant, panel reactive antibody <20%, human leukocyte antigen mismatches ≤3) with each group containing recipients of mate-kidneys from same donor and differed by induction received: group 1: no induction vs interleukin-2 receptor antibody (IL2RA) induction; group 2: no induction vs depleting antibody induction; group 3: IL2RA vs depleting antibody induction. Outcomes were compared between mate-kidney recipients in each group in an adjusted model. Total of 1034 mate-kidney recipients were identified: group 1, n = 192; group 2, n = 362 and group 3, n = 480. Adjusted risk for DGF was higher (OR 1.89, 95% CI 1.09-3.25,.P = 0.02) and one-year acute rejection trended lower (OR 0.53, 95% CI 0.25-1.11, P = 0.09) among depleting antibody induced patients in group 2. Adjusted five-year graft survivals were similar between mate-kidney recipients in all three groups. Adjusted patient death risk was significantly lower in depleting antibody induced patients in group 2 (HR 0.48, 95% CI 0.26-0.88, P = 0.02) and trended lower in IL2RA induced patient in group 1 (HR 0.32, 95% CI 0.10-1.01, P = 0.05). Perioperative antibody induction was associated with lower patient death risk in low-immunologic risk KTRs.