Kidney nonprocurement in solid organ donors in the United States

Kidney Transplant Outcomes From Deceased Donors Who Received Dialysis

Importance

Recipient outcomes after kidney transplant from deceased donors who received dialysis prior to kidney donation are not well described.

Objective

To compare outcomes of transplant recipients who received kidneys from deceased donors who underwent dialysis prior to kidney donation vs recipients of kidneys from deceased donors who did not undergo dialysis.

Design, Setting, and Participants

A retrospective cohort study was conducted including data from 58 US organ procurement organizations on deceased kidney donors and kidney transplant recipients. From 2010 to 2018, 805 donors who underwent dialysis prior to kidney donation were identified. The donors who underwent dialysis prior to kidney donation were matched 1:1 with donors who did not undergo dialysis using a rank-based distance matrix algorithm; 1944 kidney transplant recipients were evaluated.

Exposure

Kidney transplants from deceased donors who underwent dialysis prior to kidney donation compared with kidney transplants from deceased donors who did not undergo dialysis.

Main Outcomes and Measures

The 4 study outcomes were delayed graft function (defined as receipt of dialysis by the kidney recipient ≤1 week after transplant), all-cause graft failure, death-censored graft failure, and death.

Results

From 2010 to 2018, 1.4% of deceased kidney donors (805 of 58 155) underwent dialysis prior to kidney donation. Of these 805 individuals, 523 (65%) donated at least 1 kidney. A total of 969 kidneys (60%) were transplanted and 641 kidneys (40%) were discarded. Among the donors with kidneys transplanted, 514 (mean age, 33 years [SD, 10.8 years]; 98 had hypertension [19.1%] and 36 had diabetes [7%]) underwent dialysis prior to donation and were matched with 514 (mean age, 33 years [SD, 10.9 years]; 98 had hypertension [19.1%] and 36 had diabetes [7%]) who did not undergo dialysis. Kidney transplants from donors who received dialysis prior to donation (n = 954 kidney recipients) were associated with a higher risk of delayed graft function compared with kidney transplants from donors who did not receive dialysis (n = 990 kidney recipients) (59.2% vs 24.6%, respectively; adjusted odds ratio, 4.17 [95% CI, 3.28-5.29]). The incidence rates did not significantly differ at a median follow-up of 34.1 months for all-cause graft failure (43.1 kidney transplants per 1000 person-years from donors who received dialysis prior to donation vs 46.9 kidney transplants per 1000 person-years from donors who did not receive dialysis; adjusted hazard ratio [HR], 0.90 [95% CI, 0.70-1.15]), for death-censored graft failure (22.5 vs 20.6 per 1000 person-years, respectively; adjusted HR, 1.18 [95% CI, 0.83-1.69]), or for death (24.6 vs 30.8 per 1000 person-years; adjusted HR, 0.76 [95% CI, 0.55-1.04]).

Conclusions and Relevance

Compared with receiving a kidney from a deceased donor who did not undergo dialysis, receiving a kidney from a deceased donor who underwent dialysis prior to kidney donation was associated with a significantly higher incidence of delayed graft function, but no significant difference in graft failure or death at follow-up.

Organ Utilization Rates from Non-Ideal Donors for Solid Organ Transplant in the United States

Background: Non-ideal donors provide acceptable allografts and may expand the donor pool. This study evaluates donor utilization across solid organs over 15-years in the United States. Methods: We analyzed the OPTN STAR database to identify potential donors across three donor eras: 2005-2009, 2010-2014, and 2015-2019. Donors were analyzed by a composite Donor Utilization Score (DUS), comprised of donor age and comorbidities. Outcomes of interest were overall and organ-specific donor utilization. Descriptive analyses and multivariable logistic regression modeling were performed. p-values < 0.01 considered significant. Results: Of 132,465 donors, 32,710 (24.7%) were identified as non-ideal donors (NID), based on a DUS ≥ 3. Compared to ideal donors (ID), NID were older (median 56 years, IQR 51-64 years vs. 35 years, 22-48 years, p < 0.001) and more frequently female (44.3% vs. 39.1%, p < 0.001), Black (22.1% vs. 14.6%, p < 0.001) and obese (60.7% vs. 19.6%, p < 0.001). The likelihood of overall DBD utilization from NID increased from Era 1 to Era 2 (OR 1.227, 95% CI 1.123-1.341, p < 0.001) and Era 3 (OR 1.504, 1.376-1.643, p < 0.001), while DCD donor utilization in NID was not statistically different across Eras. Compared to Era 1, the likelihood of DBD utilization from NID for kidney transplantation was lower in Era 2 (OR 0.882, 0.822-0.946) and Era 3 (OR 0.938, 0.876-1.004, p = 0.002). The likelihood of NID utilization increased in Era 3 compared to Era 1 for livers (OR 1.511, 1.411-1.618, p < 0.001), hearts (OR 1.623, 1.415-1.862, p < 0.001), and lungs (OR 2.251, 2.011-2.520, p < 0.001). Conclusions: Using a universal definition of NID across organs, NID donor utilization is increasing; however, use of DUS may improve resource utilization in identifying donors at highest likelihood for multi-organ donation.

Decreased Utilization Rate of Grafts for Liver Transplantation After Implementation of Acuity Circle-based Allocation

BACKGROUND

The allocation system for livers began using acuity circles (AC) in 2020. In this study, we sought to evaluate the impact of AC policy on the utilization rate for liver transplantation (LT).

METHODS

Using the US national registry data between 2018 and 2022, LTs were equally divided into 2 eras: pre-AC (before February 4, 2020) and post-AC (February 4, 2020, and after). Deceased potential liver donors were defined as deceased donors from whom at least 1 organ was procured.

RESULTS

The annual number of deceased potential liver donors increased post-AC (from 10 423 to 12 259), approaching equal to that of new waitlist registrations for LT (n = 12 801). Although the discard risk index of liver grafts was comparable between the pre- and post-AC eras, liver utilization rates in donation after brain death (DBD) and donation after circulatory death (DCD) donors were lower post-AC ( P  < 0.01; 79.8% versus 83.4% and 23.7% versus 26.0%, respectively). Recipient factors, ie, no recipient located, recipient determined unsuitable, or time constraints, were more likely to be reasons for nonutilization after implementation of the AC allocation system compared to the pre-AC era (20.0% versus 12.3% for DBD donors and 50.1% versus 40.8% for DCD donors). Among non-high-volume centers, centers with lower utilization of marginal DBD donors or DCD donors were more likely to decrease LT volume post-AC.

CONCLUSIONS

Although the number of deceased potential liver donors has increased, overall liver utilization among deceased donors has decreased in the post-AC era. To maximize the donor pool for LT, future efforts should target specific reasons for liver nonutilization.

Histological and clinical evaluation of discarded kidneys in a European cohort of deceased brain death donor kidneys of marginal quality

BACKGROUND

Despite organ shortages, the discard rate of deceased donor kidneys is high. Risk factors for this trend warrant further study.

METHODS

We investigated reasons for discard in a cohort of brain death donors with marginal kidneys and procurement biopsies. Paraffin embedded procurement biopsies were systematically reevaluated and graded for the purpose of the study. Assessment included percentage of global glomerulosclerosis, Banff Lesion scores and tubular epithelial damage. Donor-, transplant process-, perfusion quality-, histopathology-, and recipient-related parameters were compared between discarded and transplanted organs.

RESULTS

Although most clinical characteristics were similar between donors whose kidneys were transplanted and those whose kidneys were procured but discarded, discarded kidneys were more likely to be from donors with hepatitis C, to have undergone wedge biopsies, to show changes of acute and chronic injury and to be deemed poor quality. Except for obvious anatomic abnormalities, kidneys were often discarded due to the findings of procurement biopsies. Donors of kidneys discarded for histologic reasons more often had hypertension, coronary artery disease, stroke, and increased serum creatinine. The reason for discard was unknown in 20% of cases. Discarded kidneys came from donors who appeared to be clinically similar to donors whose kidneys were utilized for transplant.

CONCLUSION

A considerable proportion of discarded kidneys were of acceptable quality. The analysis of the outcome of every recovered organ could help to overcome this problem. Procurement biopsies more often lead to discard than to transplantation of recovered organs. Proper handling during allocation has to be determined.

Single center experience and literature review of kidney transplantation from non-ideal donors with acute kidney injury: Risk and reward

INTRODUCTION

There is limited experience transplanting kidneys from either expanded criteria donors (ECD) or donation after circulatory death (DCD) deceased donors with terminal acute kidney injury (AKI).

METHODS

AKI kidneys were defined by a donor terminal serum creatinine level >2.0 mg/dL whereas non-ideal deceased donor (NIDD) kidneys were defined as AKI/DCD or AKI/ECDs.

RESULTS

From February 2007 to March 2023, we transplanted 266 single AKI donor kidneys including 29 from ECDs, 29 from DCDs (n = 58 NIDDs), and 208 from brain-dead standard criteria donors (SCDs). Mean donor age (43.7 NIDD vs. 33.5 years SCD), KDPI (66% NIDD vs. 45% SCD), and recipient age (57 NIDD vs. 51 years SCD) were higher in the NIDD group (all p < .01). Mean waiting times (17.8 NIDD vs. 24.2 months SCD) and dialysis duration (34 NIDD vs. 47 months SCD) were shorter in the NIDD group (p < .05). Delayed graft function (DGF, 48%) and 1-year graft survival (92.7% NIDD vs. 95.9% SCD) was similar in both groups. Five-year patient and kidney graft survival rates were 82.1% versus 89.9% and 82.1% versus 75.2% (both p = NS) in the NIDD versus SCD groups, respectively.

CONCLUSIONS

The use of kidneys from AKI donors can be safely liberalized to include selected ECD and DCD donors.

Past, Current, and Future Perspectives on Transplanting Acute Kidney Injury Kidneys

(1) Background: Acute kidney injury (AKI) kidneys have high non-utilization rates due to concerns regarding unfavorable outcomes. In this paper, we aimed to review the past, present, and future opinions on AKI kidneys. (2) Methods: A PubMed search was conducted for topics relevant to AKI kidney transplantation. (3) Results: Current short- and long-term data on AKI kidneys have demonstrated good outcomes including favorable graft function and survival. The role of procurement biopsies is controversial, but they have been shown to be beneficial in AKI kidneys by allowing clinicians to differentiate between reversible tubular injury and irreversible cortical necrosis. Machine perfusion has also been applied to AKI kidneys and has been shown to reduce delayed graft function (DGF). The incidence of DGF increases with AKI severity and its management can be challenging. Strategies employed to counteract this have included early initiation of dialysis after kidney transplantation, early targeting of adequate immunosuppression levels to minimize rejection risk, and establishment of outpatient dialysis. (4) Conclusions: Despite good outcomes, there continue to be barriers that impact AKI kidney utilization. Successful strategies have included use of procurement biopsies or machine perfusion and expectant management of DGF. With increasing experience, better use of AKI kidneys can result in additional opportunities to expand the donor pool.

A Retrospective Evaluation of Changing Health Characteristics Amongst Deceased Organ Donors in the United States

BACKGROUND

The availability of suitable donor organs remains a limiting factor to performing life-saving transplant operations. This study evaluates changes in the health of the donor population and its influence on organ use in the United States.

METHODS

A retrospective analysis was performed using the OPTN STAR data file from 2005 to 2019. Three donor eras were defined: 1) 2005 to 2009, 2) 2010 to 2014, and 3) 2015 to 2019. The primary outcome was donor use, defined as transplantation of at least one solid organ. Descriptive analyses were performed, and associations of donor use were examined with multivariable logistic regression models. P values <.01 were considered significant.

RESULTS

The cohort included 132,783 potential donors of which 124,729 (93.9%) were used for transplantation. Donor median age was 42 years (interquartile range 26-54), 53,566 (40.3%) were female, and 88,209 (66.4%) were White, 21,834 (16.4%) were black, and 18,509 (13.9%) were Hispanic. Compared with donors from Eras 1 and 2, donors in Era 3 were younger (P < .001), had higher body mass index (BMI) (P < .001), increased rates of diabetes mellitus (DM) (P < .001), hepatitis C virus (HCV) positivity (P < .001) and more comorbidities (P < .001). Multivariable modeling found donor BMI, DM, hypertension, and HCV status as health factors significantly associated with donor use. Compared with Era 1, there was increased use in Era 3 of donors with BMI ≥30 kg/m², DM, hypertension, HCV-positive status, and donors with ≥3 comorbidities.

CONCLUSIONS

Despite an increasing prevalence of chronic health problems in the donor population, donors with multiple comorbid conditions are more likely to be used for transplantation in recent years.

Long-term outcomes of kidney transplantation from deceased donors with terminal acute kidney injury: Single center experience and literature review

INTRODUCTION

Long-term outcomes of kidney transplantation from deceased donors (DDKTs) with terminal acute kidney injury (AKI) are not well defined.

METHODS

Single center retrospective review of DDKTs from 1/31/07-12/31/19. AKI kidneys were defined by a doubling of the donor's admission serum creatinine (SCr) level AND a terminal SCr ≥2.0 mg/dl.

RESULTS

A total of 188 AKI DDKTs were performed, including 154 from brain-dead standard criteria donors (SCD). Mean donor age was 36 years and mean Kidney Donor Profile Index was 50%; mean admission and terminal SCr levels were 1.3 and 3.1 mg/dl, respectively. With a mean follow-up of 94 months (median 89 months), overall patient (both 71.3%) and graft survival (54% AKI vs. 57% non-AKI) rates were comparable to concurrent DDKTs from brain-dead non-AKI SCDs (n = 769). Delayed graft function (DGF) was higher in AKI kidney recipients (47% vs. 20% non-AKI DDKTs, p < .0001). DGF was associated with lower graft survival in recipients of both AKI and non-AKI SCD kidneys but the impact was earlier and more pronounced in non-AKI recipients.

CONCLUSIONS

Despite having more than twice the incidence of DGF, kidneys from deceased donors with terminal AKI have long-term outcomes comparable to non-AKI SCD kidneys and represent a safe and effective method to expand the donor pool.

DCD Hepatitis C Virus-positive Donor Livers Can Achieve Favorable Outcomes With Liver Transplantation and Are Underutilized

BACKGROUND

Hepatitis C virus (HCV)-positive donors (antibody-positive [Ab + ] or nucleic acid test positive [NAT + ] donors) have been underutilized. The aim of this study was to evaluate the utilization of livers from HCV-positive with donation after circulatory death (DCD) and to assess outcomes in recipients of these grafts.

METHODS

Data between 2015 and 2019 were obtained from the United Network for Organ Sharing database. The utilization rates and graft survival among 8455 DCD liver and nonliver donors and 2278 adult DCD liver transplantation (LT) recipients were reviewed on the basis of donor HCV Ab/NAT status.

RESULTS

The utilization of Ab + /NAT - donors <40 y and Ab + /NAT + donors ≥40 y was low than utilization of HCV-negative donors ( P  < 0.001). Multivariate analysis identified HCV status (odds ratio [OR], 1.62; 95% confidence interval [CI], 1.06-2.48 in Ab + /NAT - , and OR, 1.49; 95% CI, 1.09-2.05 in Ab + /NAT + ) as an independent predictor of nonutilization of liver grafts. The rate of significant liver fibrosis was comparable in Ab + /NAT - (3.5%; P  = 0.84) but was higher in Ab + /NAT + (8.7%; P  = 0.03) than that in Ab - /NAT - donors. Kaplan-Meier survival curves demonstrated comparable 3-y patient survival in recipients of HCV-positive grafts compared with recipients of HCV-negative grafts ( P  = 0.63; 85.6% in Ab - /NAT - , 80.4% in Ab + /NAT - , and 88.7% in Ab + /NAT + ).

CONCLUSIONS

Patient and graft survival rates are similar between HCV-positive and HCV-negative DCD LT. However, HCV-positive donors are particularly underutilized for DCD LT.

Deceased-Donor Acute Kidney Injury and Acute Rejection in Kidney Transplant Recipients: A Multicenter Cohort

RATIONALE & OBJECTIVE

Donor acute kidney injury (AKI) activates innate immunity, enhances HLA expression in the kidney allograft, and provokes recipient alloimmune responses. We hypothesized that injury and inflammation that manifested in deceased-donor urine biomarkers would be associated with higher rates of biopsy-proven acute rejection (BPAR) and allograft failure after transplantation.

STUDY DESIGN

Prospective cohort.

SETTING & PARTICIPANTS

862 deceased donors for 1,137 kidney recipients at 13 centers.

EXPOSURES

We measured concentrations of interleukin 18 (IL-18), kidney injury molecule 1 (KIM-1), and neutrophil gelatinase-associated lipocalin (NGAL) in deceased donor urine. We also used the Acute Kidney Injury Network (AKIN) criteria to assess donor clinical AKI.

OUTCOMES

The primary outcome was a composite of BPAR and graft failure (not from death). A secondary outcome was the composite of BPAR, graft failure, and/or de novo donor-specific antibody (DSA). Outcomes were ascertained in the first posttransplant year.

ANALYTICAL APPROACH

Multivariable Fine-Gray models with death as a competing risk.

RESULTS

Mean recipient age was 54 ± 13 (SD) years, and 82% received antithymocyte globulin. We found no significant associations between donor urinary IL-18, KIM-1, and NGAL and the primary outcome (subdistribution hazard ratio [HR] for highest vs lowest tertile of 0.76 [95% CI, 0.45-1.28], 1.20 [95% CI, 0.69-2.07], and 1.14 [95% CI, 0.71-1.84], respectively). In secondary analyses, we detected no significant associations between clinically defined AKI and the primary outcome or between donor biomarkers and the composite outcome of BPAR, graft failure, and/or de novo DSA.

LIMITATIONS

BPAR was ascertained through for-cause biopsies, not surveillance biopsies.

CONCLUSIONS

In a large cohort of kidney recipients who almost all received induction with thymoglobulin, donor injury biomarkers were associated with neither graft failure and rejection nor a secondary outcome that included de novo DSA. These findings provide some reassurance that centers can successfully manage immunological complications using deceased-donor kidneys with AKI.

Early Effect of the Circular Model of Kidney Allocation in the United States

BACKGROUND

In March 2021, the United States implemented a new kidney allocation system (KAS250) for deceased donor kidney transplantation (DDKT), which eliminated the donation service area-based allocation and replaced it with a system on the basis of distance from donor hospital to transplant center within/outside a radius of 250 nautical miles. The effect of this policy on kidney discards and logistics is unknown.

METHODS

We examined discards, donor-recipient characteristics, cold ischemia time (CIT), and delayed graft function (DGF) during the first 9 months of KAS250 compared with a pre-KAS250 cohort from the preceding 2 years. Changes in discards and CIT after the onset of COVID-19 and the implementation of KAS250 were evaluated using an interrupted time-series model. Changes in allocation practices (biopsy, machine perfusion, and virtual cross-match) were also evaluated.

RESULTS

Post-KAS250 saw a two-fold increase in kidneys imported from nonlocal organ procurement organizations (OPO) and a higher proportion of recipients with calculated panel reactive antibody (cPRA) 81%-98% (12% versus 8%; P <0.001) and those with >5 years of pretransplant dialysis (35% versus 33%; P <0.001). CIT increased (mean 2 hours), including among local OPO kidneys. DGF was similar on adjusted analysis. Discards after KAS250 did not immediately change, but we observed a statistically significant increase over time that was independent of donor quality. Machine perfusion use decreased, whereas reliance on virtual cross-match increased, which was associated with shorter CIT.

CONCLUSIONS

Early trends after KAS250 show an increase in transplant access to patients with cPRA>80% and those with longer dialysis duration, but this was accompanied by an increase in CIT and a suggestion of worsening kidney discards.

Revisiting the "Weekend Effect" on Adult and Pediatric Liver and Kidney Offer Acceptance

BACKGROUND Weekends can impose resource and manpower constraints on hospitals. Studies using data from prior allocation schemas showed increased adult organ discards on weekends. We examined the impact of day of the week on adult and pediatric organ acceptance using contemporary data. MATERIAL AND METHODS Retrospective analysis of UNOS-PTR match-run data of all offers for potential kidney and liver transplant from 1/1/2016 to 7/1/2021 were examined to study the rate at which initial offers were declined depending on day of the week. Risk factors for decline were also evaluated. RESULTS Of the total initial adult/pediatric liver and kidney offers, the fewest offers occurred on Mondays and Sundays. The decline rate for adult/pediatric kidneys was highest on Saturdays and lowest on Tuesdays. The decline rate for adult livers was highest on Saturday and lowest on Wednesday. In contrast, the decline rate for pediatric livers was highest on Tuesdays and lowest on Wednesdays. Independent risk factors from multivariate analysis of the adult/pediatric kidney and liver decline rate were analyzed. The weekend offer remains an independent risk factor for adult kidney and liver offer declines, but for pediatric offers, these were not significant independent risk factors. CONCLUSIONS Although allocation systems have changed, and the availability of kidneys and livers have increased in the USA over the past 5 years, the weekend effect remains significant for adult liver and kidney offers for declines. Interestingly, the weekend effect was not seen for pediatric liver and kidney offers.

Kidney nonprocurement in deceased donors with acute kidney injury

BACKGROUND

Acute kidney injury (AKI) is common in deceased organ donors and is associated with high rates of kidney discard by transplant centers. High discard rates may consequently drive nonprocurement of these kidneys by organ procurement organizations. We aimed to study the relationship between donor AKI and kidney nonprocurement.

METHODS

Using U.S. registry data, we identified donors with at least one organ recovered from 2008 to 2018. We compared characteristics of donors with no kidneys procured across AKI stages, and used multivariable logistic regression to evaluate the relationship between AKI severity and kidney nonprocurement.

RESULTS

Overall 14 543 kidneys from 7620 donors were not procured, among which 93% were from donors with AKI. For 6945 donors with no kidneys procured but an extrarenal organ recovered, most had stage 3 (51%), followed by stage 1 (27%) and stage 2 AKI (15%). Nonprocured stage 3 donors were the youngest and had the lowest Kidney Donor Risk Index of all nonprocured donors. Adjusted odds of kidney nonprocurement were 1.14 (95%CI 1.02-1.27) for stage 1, 1.25 (95%CI 1.12-1.41) for stage 2, and 10.37 (95%CI 9.30-11.56) for stage 3 donors, compared to non-AKI donors. Among donors with minimum creatinine <1.5 mg/dl, stage 2 and 3 AKI were still associated with significantly higher odds of nonprocurement.

CONCLUSIONS

AKI severity is a strong risk factor for kidney nonprocurement. Efforts to address the organ shortage should focus on encouraging procurement and utilization of kidneys from deceased donors with severe AKI, given the large and rising prevalence of donor AKI and excellent transplant outcomes with these kidneys.

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.

Implications of Accumulated Cold Time for US Kidney Transplantation Offer Acceptance

BACKGROUND AND OBJECTIVES

Reducing discard is important for the US transplantation system because nearly 20% of the deceased donor kidneys are discarded. One cause for the discards is the avoidance of protracted cold ischemia times. Extended cold ischemia times at transplant are associated with additional risk of graft failure and patient mortality. A preference for local (within the same donor service area) or low-Kidney Donor Risk Index organs, the endogeneity of cold ischemia time during organ allocation, and the use of provisional offers all complicate the analysis of cold ischemia times' influence on kidney acceptance decision making.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Using January 2018 to June 2019 Organ Procurement and Transplantation Network data, we modeled the probability of accepting an offer for a kidney after provisional acceptance. We use logistic regression that includes cold ischemia time, Kidney Donor Risk Index, and other covariates selected from literature. Endogeneity of cold ischemia time was treated by a two-stage instrumental variables approach.

RESULTS

Logistic regression results for 3.33 million provisional acceptances from 12,369 donors and 108,313 candidates quantify trade-offs between cold ischemia time at the time of offer acceptance and donor-recipient characteristics. Overall, each additional 2 hours of cold ischemia time affected acceptance for nonlocal and local recipients (odds ratio, 0.75; 95% confidence interval, 0.73 to 0.77, odds ratio, 0.88; 95% confidence interval, 0.86 to 0.91; P<0.001). For Kidney Donor Risk Index >1.75 (Kidney Donor Profile Index >85) kidneys, an additional 2 hours of cold ischemia time for nonlocal and local recipients was associated with acceptance with odds ratio, 0.58; 95% confidence interval, 0.54 to 0.63 (nonlocal) and odds ratio, 0.65; 95% confidence interval, 0.6 to 0.7 (local); P<0.001. The effect of an additional 2 hours of cold ischemia time on acceptance of kidneys with Kidney Donor Risk Index ≤1.75 (Kidney Donor Profile Index ≤85) was less pronounced for nonlocal offers (odds ratio, 0.82; 95% confidence interval, 0.80 to 0.85; P<0.001) and not significant for local offers.

CONCLUSIONS

The acceptability of marginal organs was higher when placements were nearer to the donor and when cold ischemia time was shorter.

Examining utilization of kidneys as a function of procurement performance

Questions have arisen around new metrics for organ procurement organizations (OPO) due to the perception that low-performing OPOs may be limited by local centers' acceptance of marginal organs. We reviewed 2013-2019 Organ Procurement and Transplantation Network (OTPN) and National Centers for Health Statistics (NCHS) data to explore the relationship between objectively measured OPO performance and utilization of deceased donor kidneys. We found that although donor recovery declined with rising age and kidney donor profile index (KDPI), OPO performance differences were evident within each age/KDPI group. By contrast, the number of discards per donor did not vary with OPO performance. Centers in donor service areas (DSAs) with lower-performing OPOs had higher local utilization and greater import of high-KDPI kidneys than did those with higher-performing OPOs. Lower rates of donor availability relative to waitlist additions may contribute to observed center acceptance behavior. Differences in center-level performance were highly visible in Scientific Registry of Transplant Recipients (SRTR) organ acceptance metrics, while SRTR OPO metrics did not detect large or persistent variation in procurement performance. Cumulatively, our findings suggest that objective measures of procurement performance can inform discussions of organ utilization, allowing for alignment of metrics in all elements of the procurement-transplantation system.

Association of transplant center market concentration and local organ availability with deceased donor kidney utilization

Although there is a shortage of kidneys available for transplantation, many transplantable kidneys are not procured or are discarded after procurement. We investigated whether local market competition and/or organ availability impact kidney procurement/utilization. We calculated the Herfindahl-Hirschman Index (HHI) for deceased donor kidney transplants (2015-2019) for 58 US donation service areas (DSAs) and defined 4 groups: HHI ≤ 0.32 (high competition), HHI = 0.33-0.51 (medium), HHI = 0.53-0.99 (low), and HHI = 1 (monopoly). We calculated organ availability for each DSA as the number kidneys procured per incident waitlisted candidate, grouped as: <0.42, 0.42-0.69, >0.69. Characteristics of procured organs were similar across groups. In adjusted logistic regression, the HHI group was inconsistently associated with composite export/discard (reference: high competition; medium: OR 1.16, 95% CI 1.11-1.20; low 1.01, 0.96-1.06; monopoly 1.19, 1.13-1.26) and increasing organ availability was associated with export/discard (reference: availability <0.42; 0.42-0.69: OR 1.35, 95% CI 1.30-1.40; >0.69: OR 1.83, 95% CI 1.73-1.93). When analyzing each endpoint separately, lower competition was associated with higher export and only market monopoly was weakly associated with lower discard, whereas higher organ availability was associated with export and discard. These results indicate that local organ utilization is more strongly influenced by the relative intensity of the organ shortage than by market competition between centers.

Deceased donor kidneys allocated out of sequence by organ procurement organizations

Deceased donor kidney allocation follows a ranked match-run of potential recipients. Organ procurement organizations (OPOs) are permitted to deviate from the mandated match-run in exceptional circumstances. Using match-run data for all deceased donor kidney transplants (Ktx) in the US between 2015 and 2019, we identified 1544 kidneys transplanted from 933 donors with an OPO-initiated allocation exception. Most OPOs (55/58) used this process at least once, but 3 OPOs performed 64% of the exceptions and just 2 transplant centers received 25% of allocation exception Ktx. At 2 of 3 outlier OPOs these transplants increased 136% and 141% between 2015 and 2019 compared to only a 35% increase in all Ktx. Allocation exception donors had less favorable characteristics (median KDPI 70, 41% with history of hypertension), but only 29% had KDPI ≥ 85% and the majority did not meet the traditional threshold for marginal kidneys. Allocation exception kidneys went to larger centers with higher offer acceptance ratios and to recipients with 2 fewer priority points-equivalent to 2 less years of waiting time. OPO-initiated exceptions for kidney allocation are growing increasingly frequent and more concentrated at a few outlier centers. Increasing pressure to improve organ utilization risks increasing out-of-sequence allocations, potentially exacerbating disparities in access to transplantation.

Clinically adjudicated deceased donor acute kidney injury and graft outcomes

BACKGROUND

Acute kidney injury (AKI) in deceased donors is not associated with graft failure (GF). We hypothesize that hemodynamic AKI (hAKI) comprises the majority of donor AKI and may explain this lack of association.

METHODS

In this ancillary analysis of the Deceased Donor Study, 428 donors with available charts were selected to identify those with and without AKI. AKI cases were classified as hAKI, intrinsic (iAKI), or mixed (mAKI) based on majority adjudication by three nephrologists. We evaluated the associations between AKI phenotypes and delayed graft function (DGF), 1-year eGFR and GF. We also evaluated differences in urine biomarkers among AKI phenotypes.

RESULTS

Of the 291 (68%) donors with AKI, 106 (36%) were adjudicated as hAKI, 84 (29%) as iAKI and 101 (35%) as mAKI. Of the 856 potential kidneys, 669 were transplanted with 32% developing DGF and 5% experiencing GF. Median 1-year eGFR was 53 (IQR: 41-70) ml/min/1.73m2. Compared to non-AKI, donors with iAKI had higher odds DGF [aOR (95%CI); 4.83 (2.29, 10.22)] and had lower 1-year eGFR [adjusted B coefficient (95% CI): -11 (-19, -3) mL/min/1.73 m2]. hAKI and mAKI were not associated with DGF or 1-year eGFR. Rates of GF were not different among AKI phenotypes and non-AKI. Urine biomarkers such as NGAL, LFABP, MCP-1, YKL-40, cystatin-C and albumin were higher in iAKI.

CONCLUSION

iAKI was associated with higher DGF and lower 1-year eGFR but not with GF. Clinically phenotyped donor AKI is biologically different based on biomarkers and may help inform decisions regarding organ utilization.

Association Between Deceased Donor Acute Kidney Injury Assessed Using Baseline Serum Creatinine Back-Estimation and Graft Survival: Results From the French National CRISTAL Registry

RATIONALE & OBJECTIVE

Deceased donor acute kidney injury (AKI) frequently leads to kidney discards, but its impact on long-term graft survival in kidney transplant recipients remains unclear. We investigated the association between deceased donor AKI assessed using back-estimation of baseline serum creatinine (Scr) and graft survival.

STUDY DESIGN

Observational cohort study.

SETTING & PARTICIPANTS

Adult patients represented within the French CRISTAL registry who received a single kidney allograft from brain-dead deceased donors between January 2006 and December 2017.

EXPOSURE

A back-estimated Scr baseline value was derived for an assumed glomerular filtration rate at 75mL/min/1.73m², using the MDRD Study equation. A refined classification system for donor AKI was implemented as follows: no AKI, undetermined AKI/chronic kidney disease (CKD), recovery from AKI, and ongoing AKI.

OUTCOME

Death-censored graft survival.

ANALYTICAL APPROACH

Multivariable Cox models using a robust variance estimator for paired kidneys from the same donor.

RESULTS

We classified 26,786 recipients as follows: no AKI (n=19,276); undetermined AKI/CKD (n=1,745); recovery from AKI (n=2,392); and ongoing AKI (n=3,373). We observed 4,458 kidney graft losses during a median follow-up period of 5.7 years. Compared with no AKI, ongoing AKI was associated with an increased risk of graft failure (hazard ratio [HR], 1.24 [95% CI, 1.13-1.35]). The HRs for graft failure in the undetermined AKI/CKD and recovery from AKI groups (1.22 [95% CI, 1.07-1.38] and 1.18 [95% CI, 1.06-1.31], respectively) were similar to those observed in the ongoing AKI group. The adverse effect of deceased donor AKI was no longer evident when relying either on the admission or the lowest Scr throughout the procurement procedure as baseline Scr.

LIMITATIONS

No measurement of urine output in donors.

CONCLUSIONS

Deceased donor ongoing AKI, undetermined AKI/CKD, and recovery from AKI according to back-estimated baseline Scr are associated with decreased graft survival. The definition of baseline Scr as the first value measured on admission would have led to a misclassification bias and erroneous estimates.

Greater complexity and monitoring of the new Kidney Allocation System: Implications and unintended consequences of concentric circle kidney allocation on network complexity

The deceased donor kidney allocation system in the United States has undergone several rounds of iterative changes, but these changes were not explicitly designed to address the geographic variation in access to transplantation. The new allocation system, expected to start in December 2020, changes the definition of "local allocation" from the Donation Service Area to 250 nautical mile circles originating from the donor hospital. While other solid organs have adopted a similar approach, the larger number of both kidney transplant centers and transplant candidates is likely to have different consequences. Here, we discuss the incredible increase in complexity in allocation, discuss some of the likely intended and unintended consequences, and propose metrics to monitor the new system.

Left-digit bias and deceased donor kidney utilization

Cognitive biases shown to impact medical decision-making include left-digit bias, the tendency to focus on a continuous variable's leftmost digit. We hypothesized that left-digit bias impacts deceased donor kidney utilization through heuristic processing of donor age and creatinine. We used US registry data to identify 87 019 kidneys recovered (2015-2019) and compared the proportion around thresholds for donor age (69 vs. 70 years) and creatinine (1.9 vs. 2.0 mg/dl), then compared the risk of kidney discard. Kidneys from donors aged 70 vs. 69 years were more frequently discarded (77% vs. 65%, p < .001), with higher risk of discard even after adjusting for KDRI (adjusted RR 1.11, 95% CI 1.02-1.21, p = .018). Similarly, kidneys from donors with final creatinine 2.0 vs. 1.9 mg/dl were more frequently discarded (37% vs. 29%, p < .001), with higher risk of discard after adjusting for KDRI (adjusted RR 1.19, 95% CI 1.07-1.33, p = .001). However, no significant left-digit effect was found when examining other donor age (39/40, 49/50, 59/60 years) or creatinine (0.9/1.0, 2.9/3.0 mg/dl) thresholds. The findings suggest a possible left-digit effect affecting kidney utilization at specific thresholds. Additional investigations of the impact of this and other heuristics on organ utilization are needed to identify potential areas for decision-making interventions aimed at reducing kidney discard.