Hard-to-place kidney offers: Donor- and system-level predictors of discard

Kidney transplants from elderly donors: what we have learned 20 years after the Crystal City consensus criteria meeting

Based on the current projection of the general population and the combined increase in end-stage kidney disease with age, the number of elderly donors and recipients is increasing, raising crucial questions about how to minimize the discard rate of organs from elderly donors and improve graft and patient outcomes. In 2002, extended criteria donors were the focus of a meeting in Crystal City (VA, USA), with a goal of maximizing the use of organs from deceased donors. Since then, extended criteria donors have progressively contributed to a large number of transplanted grafts worldwide, posing specific issues for allocation systems, recipient management, and therapeutic approaches. This review analyzes what we have learned in the last 20 years about extended criteria donor utilization, the promising innovations in immunosuppressive management, and the molecular pathways involved in the aging process, which constitute potential targets for novel therapies.

Designing explainable AI to improve human-AI team performance: A medical stakeholder-driven scoping review

The rise of complex AI systems in healthcare and other sectors has led to a growing area of research called Explainable AI (XAI) designed to increase transparency. In this area, quantitative and qualitative studies focus on improving user trust and task performance by providing system- and prediction-level XAI features. We analyze stakeholder engagement events (interviews and workshops) on the use of AI for kidney transplantation. From this we identify themes which we use to frame a scoping literature review on current XAI features. The stakeholder engagement process lasted over nine months covering three stakeholder group's workflows, determining where AI could intervene and assessing a mock XAI decision support system. Based on the stakeholder engagement, we identify four major themes relevant to designing XAI systems - 1) use of AI predictions, 2) information included in AI predictions, 3) personalization of AI predictions for individual differences, and 4) customizing AI predictions for specific cases. Using these themes, our scoping literature review finds that providing AI predictions before, during, or after decision-making could be beneficial depending on the complexity of the stakeholder's task. Additionally, expert stakeholders like surgeons prefer minimal to no XAI features, AI prediction, and uncertainty estimates for easy use cases. However, almost all stakeholders prefer to have optional XAI features to review when needed, especially in hard-to-predict cases. The literature also suggests that providing both system- and prediction-level information is necessary to build the user's mental model of the system appropriately. Although XAI features improve users' trust in the system, human-AI team performance is not always enhanced. Overall, stakeholders prefer to have agency over the XAI interface to control the level of information based on their needs and task complexity. We conclude with suggestions for future research, especially on customizing XAI features based on preferences and tasks.

Prediction of High-Risk Donors for Kidney Discard and Nonrecovery Using Structured Donor Characteristics and Unstructured Donor Narratives

Importance

Despite the unmet need, many deceased-donor kidneys are discarded or not recovered. Inefficient allocation and prolonged ischemia time are contributing factors, and early detection of high-risk donors may reduce organ loss.

Objective

To evaluate the feasibility of machine learning (ML) and natural language processing (NLP) classification of donors with kidneys that are used vs not used for organ transplant.

Design, Setting, and Participants

This retrospective cohort study used donor information (structured donor characteristics and unstructured donor narratives) from the United Network for Organ Sharing (UNOS). All donor offers to a single transplant center between January 2015 and December 2020 were used to train and validate ML models to predict donors who had at least 1 kidney transplanted (at our center or another center). The donor data from 2021 were used to test each model.

Exposures

Donor information was provided by UNOS to the transplant centers with potential transplant candidates. Each center evaluated the donor and decided within an allotted time whether to accept the kidney for organ transplant.

Main Outcomes and Measures

Outcome metrics of the test cohort included area under the receiver operating characteristic curve (AUROC), F1 score, accuracy, precision, and recall of each ML classifier. Feature importance and Shapley additive explanation (SHAP) summaries were assessed for model explainability.

Results

The training/validation cohort included 9555 donors (median [IQR] age, 50 [36-58] years; 5571 male [58.3%]), and the test cohort included 2481 donors (median [IQR] age, 52 [40-59] years; 1496 male [60.3%]). Only 20% to 30% of potential donors had at least 1 kidney transplanted. The ML model with a single variable (Kidney Donor Profile Index) showed an AUROC of 0.69, F1 score of 0.42, and accuracy of 0.64. Multivariable ML models based on basic a priori structured donor data showed similar metrics (logistic regression: AUROC = 0.70; F1 score = 0.42; accuracy = 0.62; random forest classifier: AUROC = 0.69; F1 score = 0.42; accuracy = 0.64). The classic NLP model (bag-of-words model) showed its best metrics (AUROC = 0.60; F1 score = 0.35; accuracy = 0.59) by the logistic regression classifier. The advanced Bidirectional Encoder Representations From Transformers model showed comparable metrics (AUROC = 0.62; F1 score = 0.39; accuracy = 0.69) only after appending basic donor information. Feature importance and SHAP detected the variables (and words) that affected the models most.

Conclusions and Relevance

Results of this cohort study suggest that models using ML can be applied to predict donors with high-risk kidneys not used for organ transplant, but the models still need further elaboration. The use of unstructured data is likely to expand the possibilities; further exploration of new approaches will be necessary to develop models with better predictive metrics.

Deceased donor kidneys from higher distressed communities are significantly less likely to be utilized for transplantation

The proportion of kidneys procured for transplantation but not utilized exceeds 20% in the United States. Factors associated with nonutilization are complex, and further understanding of novel causes are critically important. We used the national Scientific Registry of Transplant Recipients data (2010-2022) to evaluate associations of Distressed Community Index (DCI) of deceased donor residence and likelihood of kidney nonutilization (n = 209 413). Deceased donors from higher distressed communities were younger, had an increased history of hypertension and diabetes, were CDC high-risk, and had higher terminal creatinine and donation after brain death. Mechanisms and circumstances of death varied significantly by DCI. The proportion of kidney nonutilization was 19.9%, which increased by DCI quintile (Q1 = 18.1% to Q5 = 21.6%). The adjusted odds ratio of nonutilization from the highest quintile DCI communities was 1.22 (95% CI = 1.16-1.28; reference = lowest DCI), which persisted stratified by donor race. Donors from highly distressed communities were highly variable by the donor service area (range: 1%-51%; median = 21%). There was no increased risk for delayed graft function or death-censored graft loss by donor DCI but modest increased adjusted hazard for overall graft loss (high DCI = 1.05; 95% CI = 1.01-1.10; reference = lowest DCI). Results indicate that donor residential distress is associated with significantly higher rates of donor kidney nonutilization with notable regional variation and minimal impact on recipient outcomes.

The Independent Effects of Kidney Length and Vascular Plaque on Ten-Year Outcomes of Extended Criteria Donor Kidney Transplants

The independent effects of deceased donor kidney length and vascular plaque on long-term graft survival are not established. Utilizing DonorNet attachments from 4,480 expanded criteria donors (ECD) recovered between 2008 and 2012 in the United States with at least one kidney biopsied and transplanted, we analyzed the relationship between kidney length and vascular plaques and 10-year hazard of all-cause graft failure (ACGF) using causal inference methods in a Cox regression framework. The composite plaque score (range 0-4) and the presence of any plaque (yes, no) was also analyzed. Kidney length was modeled both categorically (<10, 10-12, >12 cm) as well as numerically, using a restricted cubic spline to capture nonlinearity. Effects of a novel composite plaque score 4 vs. 0 (HR 1.08; 95% CI: 0.96, 1.23) and the presence of any vascular plaque (HR 1.08; 95% CI: 0.98, 1.20) were attenuated after adjustment. Likewise, we identified a potential nonlinear relationship between kidney length and the 10-year hazard of ACGF, however the strength of the relationship was attenuated after adjusting for other donor factors. The independent effects of vascular plaque and kidney length on long-term ECD graft survival were found to be minimal and should not play a significant role in utilization.

Broad organ acceptance and equitable access to early kidney transplantation

BACKGROUND

Broad organ acceptance can increase early kidney transplantation (KTX) within <1-year of dialysis initiation while improving access inequity.

METHODS

Single-center data of adult isolated deceased-donor KTX recipients between 2013 and 2020 were stratified into three 2.5-year periods before-, early after-, and late after our center's deceased-donor organ acceptance practice change, excluding a 6-month implementation period. Outcomes were assessed within five recipient subgroups based on demographic and clinical characteristics.

RESULTS

Of 704 recipients, the frequency of early KTX was 22% pre-change, 36% early post-change, and 34% late post-change. Given similar post-change frequencies of early KTX, post-change eras were combined to improve analytic power of subgroup analyses. After the organ acceptance practice change (vs. pre-change), the likelihood of early KTX increased variably within historically underserved groups, including recipients who were older (37%-39%, p = .859), Black (10%-21%, p = .136), female (21%-37%, p = .034), diabetic (13%-32%, p = .010), and BMI≥35 kg/m² (20%-34%, p = .007). Despite the practice change, Black recipients continued to experience less early KTX compared to non-Black recipients. The likelihood of delayed graft function was significantly increased (p < .001), and 1-year creatinine was significantly higher (p < .001) post-practice change, but between-era risk-adjusted death-censored graft survival was similar.

CONCLUSIONS

Transition to broader donor acceptance was associated with more early KTXs among historically underserved patient subgroups. However, the effect was non-significant among Black recipients, suggesting the need for additional strategies to impact early transplant access for this population. Studies of broad organ acceptance are needed to examine both access and outcomes.

Single-center analysis of organ offers and workload for liver and kidney allocation

The volume of abdominal organ offers received by the Baylor Simmons Transplant Institute has increased over time, resulting in a higher workload for our donor call team. To quantify the increase in organ offers, determine the characteristics of these offers, and estimate the impact on our transplant center workload, we collected center-specific organ offer data from May 2019 to July 2021 using the UNOS Center Acceptance and Refusal Evaluation Report and performed a time study that collected the number of communications and time spent on communications for organ offers made during a typical week. The total offers per month increased by 140% (270/month to 648/month), while the number of transplanted organs remained stable. In addition, the percentage of offers for organs that were never transplanted increased from 54% to 75%. In a representative week-long time study, surgeons made 505, center coordinators 590, and answering service coordinators 318 distinct communications, averaging 3, 4, and 2 communications/hour. Between November 2019 and July 2021, offer-related workload increased by an estimated 97%. These results demonstrate a sizeable inefficiency in abdominal organ allocation associated with a nonrecoverable cost to our transplant center.

Kidney utilization in the Netherlands - do we optimally use our donor organs?

BACKGROUND

To ensure optimal utilization of deceased donor kidneys, it is important to understand the precise reasons why kidneys are discarded. In this study we aimed to obtain a comprehensive overview of kidney utilization and discard during the entire donation process in the Netherlands.

METHODS

In this retrospective cohort study we analysed kidney utilization of 3856 kidneys in the Netherlands between 1 January 2015 and 31 December 2020. For every kidney that was not transplanted, we determined the moment of and reason for discard through a unique case-by-case assessment.

RESULTS

Kidney discard according to the traditional definition (procured but not transplanted) was 7.8%. However, when kidneys that seemed medically suitable at the beginning of the donation process were also included, many more potential donor kidneys were lost and the total non-utilization was 24.4%. Subjectively presumed impaired organ quality was responsible for 34.2% of all discarded kidneys. Two-thirds of kidneys discarded due to acute kidney injury (AKI) had only AKI stage 1 or 2.

CONCLUSION

The classical definition of organ discard underestimates the non-utilization of deceased donor kidneys. Strategies to improve kidney utilization could be a revision of the maximum allowed agonal time in donation after circulatory death, careful consideration in reporting and accepting kidneys from donors with AKI and a prospectively filled registry of detailed organ discard reasons, including the 'silent' non-utilization before procurement.

Kidney Transplant Outcomes after Prolonged Delayed Graft Function

Background: The protracted recovery of renal function may be an actionable marker of post-transplant adverse events, but a paucity of data are available to determine if the duration of graft recovery serves to stratify risk. Materials and Methods: Single-center data of adult-isolated deceased-donor kidney transplant (KTX) recipients between 1 July 2015 and 31 December 2018 were stratified by delayed graft function (DGF) duration, defined as time to serum creatinine < 3.0 mg/dL. Results: Of 355 kidney transplants, the time to creatinine < 3.0 mg/dL was 0−3 days among 96 cases (DGF ≤ 3), 4−10 days among 85 cases (DGF4-10), 11−20 days among 93 cases (DGF11-20), and ≥21 days for 81 cases (DGF ≥ 21). DGF ≥ 21 recipients were significantly more likely to be male, non-sensitized, and receive kidneys from donors that were older, with donation after circulatory death, non-mandatory share, hypertensive, higher KDPI, higher terminal creatinine, and longer cold and warm ischemia time. On multivariate analysis, DGF ≥ 21 was associated with a 5.73-fold increased odds of 12-month eGFR < 40 mL/min compared to DGF ≤ 3. Lesser degrees of DGF had similar outcomes. Conclusions: Prolonged DGF lasting over 20 days signifies a substantially higher risk for reduced eGFR at 1 year compared to lesser degrees of DGF, thus serving as a threshold indicator of increased risk.

Donor rhabdomyolysis, acute kidney injury and kidney transplant outcomes

BACKGROUND

Donor rhabdomyolysis may constrain kidney utilization due to anticipated unfavorable graft outcomes-especially in combination with acute kidney injury (AKI). There is a paucity of empiric data to inform organ acceptance decision-making.

METHODS

A single-center retrospective cohort study of adult transplant recipients of deceased-donor kidneys with reported donor creatine phosphokinase (CPK) levels was conducted between 2014 and 2020. Recipients of CPK ≥ 1000 U/L kidneys were propensity matched to CPK < 1000 recipients according to outcome-predictive baseline covariates, except AKI.

RESULTS

A total of 254 kidney transplants were propensity matched into CPK ≥ 1000 (n = 90) vs CPK<1000 (n = 90) groups. Transplant outcomes with high versus low CPK kidneys were similar in terms of delayed graft function (p = 0.64), 1-year estimated glomerular filtration rate <25^th percentile (p = 0.69) and mean (p = 0.58), and time to all-cause graft failure (p = 0.58). There was no interaction between AKI and high CPK for these outcomes. Extreme CPK thresholds as high as >8672 U/L were not associated with overall graft survival in the unmatched sample (p = 0.81).

CONCLUSIONS

In a single center study, donor rhabdomyolysis was not associated with short-term kidney transplant graft outcomes, nor was there an additive effect of AKI. However, studies with greater CPK and AKI severity and longer follow-up are warranted. This article is protected by copyright. All rights reserved.

Declined Offers for Deceased Donor Kidneys Are Not an Independent Reflection of Organ Quality

Background

Deceased donor kidney offers are frequently declined multiple times before acceptance for transplantation, despite significant organ shortage and long waiting times. Whether the number of times a kidney has been declined, reflecting cumulative judgments of clinicians, is associated with long-term transplant outcomes remains unclear.

Methods

In this national, retrospective cohort study of deceased donor kidney transplants in the United States from 2008 to 2015 (n=78,940), we compared donor and recipient characteristics and short- and long-term graft and patient survival outcomes grouping by the sequence number at which the kidney was accepted for transplantation. We compared outcomes for kidneys accepted within the first seven offers in the match-run, after 8-100 offers, and for hard-to-place kidneys distinguishing those requiring >100 and >1000 offers before acceptance.

Results

Harder-to-place kidneys had lower donor quality and higher rates of delayed graft function (46% among kidneys requiring >1000 offers before acceptance versus 23% among kidneys with ≤7 offers). In unadjusted models, later sequence groups had higher hazard of all-cause graft failure, death-censored graft failure, and patient mortality; however, these associations were attenuated after adjusting for Kidney Donor Risk Index (KDRI). After adjusting for donor factors already taken into consideration during allocation, and recipient factors associated with long-term outcomes, graft, and patient survival outcomes were not significantly different for the hardest-to-place kidneys compared with the easiest-to-place kidneys, with the exception of death-censored graft failure (adjusted hazard ratio, 1.16, 95% CI, 1.05 to 1.28).

Conclusion

Late sequence offers may represent missed opportunities for earlier successful transplant for the higher-priority waitlisted candidates for whom the offers were declined.

Hardest-to-place kidney transplant outcomes in the United States

The outcomes of hardest-to-place kidney transplants-accepted last in the entire match run after being refused by previous centers-are unclear, potentially translating to risk aversion and unnecessary organ discard. We aimed to determine the outcomes of hardest-to-place kidney transplants and whether the organ acceptance position on the match run sufficiently captures the risk. This is a cohort study of the United Network for Organ Sharing data of all adult kidney-only transplant recipients from deceased donors between 2007 and 2018. Multiple regression models assessed delayed graft function, graft survival, and patient survival stratified by share type: local versus shared kidney acceptance position scaled by tertile. Among 127 028 kidney transplant recipients, 92 855 received local kidneys. The remaining received shared kidneys at sequence number 1-4 (n = 12 322), 5-164 (n = 10 485) and >164 (n = 11 366). Hardest-to-place kidneys, defined as the latest acceptance group in the match-run, were associated with delayed graft function (adjusted odds ratio 1.83, 95% confidence interval [CI] 1.74-1.92) and all-cause allograft failure (adjusted hazard ratio [aHR] 1.11, 95% CI 1.04-1.17). Results of this IRB-approved study were robust to the exclusion of operational allocation bypass and mandatory shares. The hardest-to-place kidneys accepted later in the match run were associated with higher graft failure and delayed graft function.

Macroscopic assessment of the quality of cold perfusion after deceased-donor kidney procurement: A United Kingdom population-based cohort study

Concern regarding the quality of cold perfusion (QOP) during macroscopic assessment of procured kidneys is a common reason for discard. In the UK, QOP is routinely graded by both retrieving and implanting teams during back-bench surgery as: 1 (good), 2 (fair), 3 (poor) or 4 (patchy). We evaluated the association of this grading with organ utilization, graft outcomes, and agreement between teams. Data on all deceased-donor kidneys procured between January 2000 and December 2016 were analyzed for discard rates, while association with graft outcomes was studied in single adult transplants. Of 31,167 kidneys procured, 90.6%, 5.7%, 1.7%, and 2.1% were assigned grades 1, 2, 3, and 4, respectively, at retrieval. QOP was an independent risk factor of discard, with the highest rates observed in grade 3 kidneys (41.8%), compared to 6.5% in grade 1 (aOR 7.67, 95% CI 5.44-10.82, p < .001). Grading at retrieval was an independent predictor of delayed graft function (p = .019) and primary non-function (p = .001), but not long-term graft survival (p = .111). Implanting grade was an independent predictor of all three outcomes (p < .001, p < .001, and p = .002, respectively). Consistency of grading between teams was poor (Kappa = 0.179). QOP influences utilization and predicts outcomes, but a standardized and validated scoring system is required.

Allocating kidneys in optimized heterogeneous circles

Recently, the Organ Procurement and Transplant Network approved a plan to allocate kidneys within 250-nm circles around donor hospitals. These homogeneous circles might not substantially reduce geographic differences in transplant rates because deceased donor kidney supply and demand differ across the country. Using Scientific Registry of Transplant Recipients data from 2016-2019, we used an integer program to design unique, heterogeneous circles with sizes between 100 and 500 nm that reduced supply/demand ratio variation across transplant centers. We weighted demand according to wait time because candidates who have waited longer have higher priority. We compared supply/demand ratios and average travel distance of kidneys, using heterogeneous circles and 250 and 500-nm fixed-distance homogeneous circles. We found that 40% of circles could be 250 nm or smaller, while reducing supply/demand ratio variation more than homogeneous circles. Supply/demand ratios across centers for heterogeneous circles ranged from 0.06 to 0.13 kidneys per wait-year, compared to 0.04 to 0.47 and 0.05 to 0.15 kidneys per wait-year for 250-nm and 500-nm homogeneous circles, respectively. The average travel distance for kidneys using heterogeneous, and 250-nm and 500-nm fixed-distance circles was 173 nm, 134 nm, and 269 nm, respectively. Heterogeneous circles reduce geographic disparity compared to homogeneous circles, while maintaining reasonable travel distances.

Prediction of Kidney Allograft Discard Before Procurement: The Kidney Discard Risk Index

OBJECTIVES

There is an 18.9% discard rate among kidney allografts. Here, we aimed to determine predictors of kidney discard and construct an index to identify high-probability discard kidney allografts prior to procurement.

MATERIALS AND METHODS

A total of 102 246 potential kidney allograft donors from the Organ Procurement and Transplantation Network database were used in this analysis. The cohort was randomized into 2 groups. The training set included 67% of the cohort and was used to derive a predictive index for discard that comprised 21 factors identified by univariate and multivariate logistic regression analysis. The validation set included 33% and was used to internally validate the kidney discard risk index.

RESULTS

In 77.3% of donors, at least 1 kidney was used for transplant, whereas in 22.7% of donors, both kidneys were discarded. The kidney discard risk index was highly predictive of discard with a C statistic of 0.89 (0.88-0.89). The bottom 10th percentile had a discard rate of 0.73%, whereas the top 10th percentile had a discard rate of 83.65%. The 3 most predictive factors for discard were age, creatinine level, and hepatitis C antibody status.

CONCLUSIONS

We identified 21 factors predictive of discard prior to donor procurement and used these to develop a kidney discard risk index with a C statistic of 0.89.

Degree of Glomerulosclerosis in Procurement Kidney Biopsies from Marginal Donor Kidneys and Their Implications in Predicting Graft Outcomes

Background: This study aimed to assess the association between the percentage of glomerulosclerosis (GS) in procurement allograft biopsies from high-risk deceased donor and graft outcomes in kidney transplant recipients. Methods: The UNOS database was used to identify deceased-donor kidneys with a kidney donor profile index (KDPI) score > 85% from 2005 to 2014. Deceased donor kidneys were categorized based on the percentage of GS: 0-10%, 11-20%, >20% and no biopsy performed. The outcome included death-censored graft survival, patient survival, rate of delayed graft function, and 1-year acute rejection. Results: Of 22,006 kidneys, 91.2% were biopsied showing 0-10% GS (58.0%), 11-20% GS (13.5%), >20% GS (19.7%); 8.8% were not biopsied. The rate of kidney discard was 48.5%; 33.6% in 0-10% GS, 68.9% in 11-20% GS, and 77.4% in >20% GS. 49.8% of kidneys were discarded in those that were not biopsied. Death-censored graft survival at 5 years was 75.8% for 0-10% GS, 70.9% for >10% GS, and 74.8% for the no biopsy group. Among kidneys with >10% GS, there was no significant difference in death-censored graft survival between 11-20% GS and >20% GS. Recipients with >10% GS had an increased risk of graft failure (HR = 1.27, p < 0.001), compared with 0-10% GS. There was no significant difference in patient survival, acute rejection at 1-year, and delayed graft function between 0% and 10% GS and >10% GS. Conclusion: In >85% KDPI kidneys, our study suggested that discard rates increased with higher percentages of GS, and GS >10% is an independent prognostic factor for graft failure. Due to organ shortage, future studies are needed to identify strategies to use these marginal kidneys safely and improve outcomes.

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.

Examining the Increased Rates of Deceased Donor Kidney Nonutilization in Australia: What Has Changed?

BACKGROUND

From 2013, Australia has experienced a sustained increase in the proportion of deceased donor kidneys that are retrieved but not utilized for transplantation. We aimed to determine whether this could be explained by changes in donor characteristics over time.

METHODS

Registry data were used to examine predictors of kidney nonutilization over the period 2005-2017. Multilevel mixed effect logistic regression modeling and propensity score analysis were used to determine whether era of donation (2013-2017 versus 2005-2012) was an independent predictor of organ nonutilization after controlling for donor characteristics.

RESULTS

A total of 7810 kidneys were retrieved for the purpose of transplantation with 334 (4.3%) not utilized. The nonutilization rate was 5.8% in 2013-2017 compared to 2.7% in 2005-2012. Despite adjustment for donor characteristics, donation in the more recent era remained a significant predictor of kidney nonutilization (adjusted odds ratio, 1.98; 95% confidence interval, 1.54-2.54; P < 0.001). This finding was confirmed in the propensity score analysis.

CONCLUSIONS

Kidneys retrieved in Australia since 2013 were more likely not to be utilized for transplantation even after adjusting for changes in donor characteristics. The abrupt increase may be explained by increased clinical risk aversion, changes in unmeasured donor factors or logistical issues. Although nonutilization rates in Australia remain low by international standards, further clinical auditing of the reasons for offer decline may help to optimize resource utilization and maximize transplant opportunities.

Association of Dialysis Duration With Outcomes After Kidney Transplantation in the Setting of Long Cold Ischemia Time

Background

There is no mechanism that matches hard-to-place kidneys with the most appropriate candidate. Thus, unwanted kidney offers are typically to recipients with long renal replacement time (vintage) which is a strong risk factor for mortality and graft failure, and in combination with prolonged cold ischemia time (CIT), may promote interactive effects on outcomes.

Methods

Consecutive adult isolated kidney transplants between October 2015 and December 2017 were stratified by vintage younger than 1 year and CIT longer than 30 hours.

Results

Long (n = 169) relative to short (n = 93) vintage recipients were significantly more likely to be younger (32.2 years vs 56.9 years, P = 0.02), black race (40.8% vs 18.3%, P = 0.02), have higher estimated posttransplant survival (52.6 vs 42.0, P = 0.04), and have a comorbid condition (45.6% vs 30.1%, P = 0.02); they were less likely to receive a donation after circulatory death kidney (27.8% vs 39.8%, P = 0.05). Long vintage was significantly associated with length of stay longer than 4 days (45.5% vs 30.1%, P = 0.02), and 30-day readmission (37.3% vs 22.6%, P = 0.02) but not additional operations (17.8% vs 15.1%, P = 0.58), short-term patient mortality (3.0% vs 2.2%, P = 0.70), or overall graft survival (P = 0.23). On multivariate logistic regression, long vintage remained an independent risk factor for 30-day readmission (adjusted odds ratio, 1.92; 95% confidence interval, 1.06-3.47); however, there was no interaction of vintage and CIT for this outcome (P = 0.84).

Conclusions

Readmission is significantly associated with pretransplant dialysis duration; however, CIT is not a modifying factor for this outcome.