Procurement Biopsy Findings Versus Kidney Donor Risk Index for Predicting Renal Allograft Survival

Association between Kidney Donor Risk Index, kidney graft function and histological changes in early post-transplant graft biopsy

Background

Proper assessment of donor organ quality is crucial for optimal kidney allocation and best long-term outcomes. The aim of this study was to analyze the association between the Kidney Donor Risk Index (KDRI) and histological parameters in early post-transplant graft biopsy in a Polish cohort of kidney transplant recipients.

Methods

In 418 consecutive kidney transplant recipients, a histological evaluation of very early [at median 11 (9-13) post-transplant day] protocol core needle biopsy was performed and analyzed according to the Banff classification. Subjects were divided into quartiles of the KDRI value. Kidney graft function, patient and graft survival were also analyzed over a median follow-up period of 44 (26-56) months.

Results

There was a significant trend toward greater intensity of chronic histology changes along the KDRI quartiles (χ2 = 20.8; P < .001), including interstitial fibrosis, tubular atrophy, mesangial matrix increase and arteriolar hyalinosis. Stepwise multivariate regression analysis revealed that only higher KDRI value independently increased the severity of chronic graft injury (rpartial = 0.340, P < .001). KDRI values were valuable in the determination of both early and long-term graft function.

Conclusion

The KDRI values correlate with chronic histological changes found in early post-implantation kidney biopsies and can also be helpful in the prediction of graft outcome.

Artificial Intelligence Advances in Transplant Pathology

Transplant pathology plays a critical role in ensuring that transplanted organs function properly and the immune systems of the recipients do not reject them. To improve outcomes for transplant recipients, accurate diagnosis and timely treatment are essential. Recent advances in artificial intelligence (AI)-empowered digital pathology could help monitor allograft rejection and weaning of immunosuppressive drugs. To explore the role of AI in transplant pathology, we conducted a systematic search of electronic databases from January 2010 to April 2023. The PRISMA checklist was used as a guide for screening article titles, abstracts, and full texts, and we selected articles that met our inclusion criteria. Through this search, we identified 68 articles from multiple databases. After careful screening, only 14 articles were included based on title and abstract. Our review focuses on the AI approaches applied to four transplant organs: heart, lungs, liver, and kidneys. Specifically, we found that several deep learning-based AI models have been developed to analyze digital pathology slides of biopsy specimens from transplant organs. The use of AI models could improve clinicians' decision-making capabilities and reduce diagnostic variability. In conclusion, our review highlights the advancements and limitations of AI in transplant pathology. We believe that these AI technologies have the potential to significantly improve transplant outcomes and pave the way for future advancements in this field.

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.

Pretransplant kidney transcriptome captures intrinsic donor organ quality and predicts 24-month outcomes

With the development of novel prognostic tools derived from omics technologies, transplant medicine is entering the era of precision medicine. Currently, there are no established predictive biomarkers for posttransplant kidney function. A total of 270 deceased donor pretransplant kidney biopsies were collected and posttransplant function was prospectively monitored. This study first assessed the utility of pretransplant gene expression profiles in predicting 24-month outcomes in a training set (n = 174). Nearly 600 differentially expressed genes were associated with 24-month graft function. Grafts that progressed to low function at 24 months exhibited upregulated immune responses and downregulated metabolic processes at pretransplantation. Using penalized logistic regression modeling, a 55 gene model area under the receiver operating curve (AUROC) for 24-month graft function was 0.994. Gene expression for a subset of candidate genes was then measured in an independent set of pretransplant biopsies (n = 96) using quantitative polymerase chain reaction. The AUROC when using 13 genes with three donor characteristics (age, race, body mass index) was 0.821. Subsequently, a risk score was calculated using this combination for each patient in the validation cohort, demonstrating the translational feasibility of using gene markers as prognostic tools. These findings support the potential of pretransplant transcriptomic biomarkers as novel instruments for improving posttransplant outcome predictions and associated management.

Surgeon preimplantation macroscopic graft appraisal improves risk stratification of deceased kidney donors: a prospective study

BACKGROUND

Preimplantation scores assist with correct kidney graft allocation, but macroscopic graft features have never been evaluated in this scenario.

METHODS

We designed a graft appraisal questionnaire, assessed its reproducibility by comparing the senior and junior surgeon responses and evaluated which features can predict transplant outcomes in 202 patients transplanted from 144 donors at a tertiary center. We created new prediction models in combination with validated preimplantation scores. The primary outcome was graft loss or eGFR<30 mL/min/1.73 m² at six months and secondary outcomes were delayed graft function, early graft loss and graft function at six months.

RESULTS

Interrater correlation was very good for adherent perinephric fat (kappa=0.91) and acceptable for cortical surface roughness (kappa=0.51) and cortical color (kappa=0.47). Adherent perirenal fat (Odds ratio=4.77; 95% CI: 2.10-10.85) and surface roughness (OR=2.11, 95% CI: 1.25-3.58) were independent predictors of the primary outcome, improving the kidney donor risk index efficacy model (AUC 0.71 vs. 0.82, P≤0.001), while cortical color and adherent fat improved the Irish risk model for delayed graft function (AUC 0.76 vs. 0.82, P=0.03). We created nomograms to visually assess the risk of both endpoints.

CONCLUSIONS

Kidney graft macroscopic appraisal is reproducible between surgeons and can improve the accuracy of clinical preimplantational prediction scores.

Nonutilization of Kidneys From Donors After Circulatory Determinant of Death

Background.

The expansion of donation after circulatory determination of death (DCDD) programs and unmet demands for kidney transplantation indicate that there is a need to improve the efficiency and utilization of these organs.

Methods.

We studied all DCDD donors retrieved for kidney transplantation in Australia between 2014 and 2019 and determined the factors associated with nonutilization using least absolute shrinkage and selection operator and random forest models. Self-organizing maps were used to group these donors into clusters with similar characteristics and features associated with nonutilization were defined.

Results.

Of the 762 DCDD donors, 116 (15%) were not utilized for kidney transplantation. Of the 9 clusters derived from self-organizing map, 2 had the highest proportions of nonutilized kidneys. Factors for nonutilization (adjusted odds ratio [95% confidence interval], per SD increase) were duration from withdrawal of cardiorespiratory support till death (1.38 [1.16-1.64]), admission and terminal serum creatinine (1.43 [1.13-1.85]) and (1.41 [1.16-1.73]). Donor kidney function and duration of warm ischemia were the main factors for clinical decisions taken not to use kidneys from DCDD donors.

Conclusions.

Donor terminal kidney function and the duration of warm ischemia are the key factors for nonutilization of DCDD kidneys. Strategies to reduce the duration of warm ischemia and improve post-transplant recipient kidney function may reduce rates of nonutilization.

The Independent Effects of Procurement Biopsy Findings on Ten-Year Outcomes of Extended Criteria Donor Kidney Transplants

Introduction

Methods

Results

Conclusion

The Role of Procurement Biopsies in Kidney Acceptance Decision Making and Kidney Discard: Perceptions of Physicians, Nurse Coordinators, and OPO Staff and Directors

Procurement biopsies suffer from challenges with quality and reproducibility and are linked to kidney discard. Nonetheless, procurement biopsies are obtained for the majority of kidneys in the United States, and biopsy findings are commonly relied upon in kidney acceptance decisions.

A Review of Current and Emerging Trends in Donor Graft-Quality Assessment Techniques

The number of patients placed on kidney transplant waiting lists is rapidly increasing, resulting in a growing gap between organ demand and the availability of kidneys for transplantation. This organ shortage has forced medical professionals to utilize marginal kidneys from expanded criteria donors (ECD) to broaden the donor pool and shorten wait times for patients with end-stage renal disease. However, recipients of ECD kidney grafts tend to have worse outcomes compared to those receiving organs from standard criteria donors (SCD), specifically increased risks of delayed graft function (DGF) and primary nonfunction incidence. Thus, representative methods for graft-quality assessment are strongly needed, especially for ECDs. Currently, graft-quality evaluation is limited to interpreting the donor’s recent laboratory tests, clinical risk scores, the visual evaluation of the organ, and, in some cases, a biopsy and perfusion parameters. The last few years have seen the emergence of many new technologies designed to examine organ function, including new imaging techniques, transcriptomics, genomics, proteomics, metabolomics, lipidomics, and new solutions in organ perfusion, which has enabled a deeper understanding of the complex mechanisms associated with ischemia-reperfusion injury (IRI), inflammatory process, and graft rejection. This review summarizes and assesses the strengths and weaknesses of current conventional diagnostic methods and a wide range of new potential strategies (from the last five years) with respect to donor graft-quality assessment, the identification of IRI, perfusion control, and the prediction of DGF.

Role of deceased donor kidney procurement biopsies in organ allocation

PURPOSE OF REVIEW

There has been an increased emphasis by the transplant community and the federal government to increase the utilization of deceased donor kidneys. Procurement biopsies during allocation are the most common reason for kidney discards. This manuscript reviews the evidence of procurement biopsies practices and utility.

RECENT FINDINGS

Procurement biopsies are performed in over half of all the kidneys recovered in the United States and account for more than one third of the kidney discards. However, there is a significant heterogeneity across the organ procurement organizations regarding the indications for biopsy, biopsy techniques and their reporting. Procurement biopsy findings are not reproducible and poorly correlate to postimplantation histology, although reasons for these limitations are not clear. Procurement biopsy findings are not associated with posttransplant outcomes after accounting for readily available donor clinical characteristics.

SUMMARY

Procurement biopsies contribute to deceased donor kidney discards but do not predict posttransplant outcomes. Research to establish the best practices for procurement biopsies is needed to improve organ utilization.

Variations in deceased donor kidney procurement biopsy practice patterns: A survey of U.S. organ procurement organizations

BACKGROUND

Procurement biopsies have become a common practice in the evaluation and allocation of deceased donor kidneys in the United States despite questions about their value and reproducibility. We sought to determine the extent of OPO-level differences in criteria used to decide which deceased donor kidneys undergo a procurement biopsy and to assess the degree of variability in procurement biopsy technique and interpretation across OPOs.

METHODS

Each of the country's 58 OPOs were invited to participate in the survey. OPOs were divided into two groups based on organ availability ratio and deceased donor kidney discard rate.

RESULTS AND CONCLUSIONS

Fifty-out-of-fifty-eight invited OPOs (86% response rate) responded to the survey between November 2020 and December 2020. Thirty (60%) OPOs reported that they have formal criteria for performing kidney procurement biopsy, but for 29 of these OPOs, transplant centers can request biopsy on kidneys that do not meet criteria. OPOs used a total of seven different variables and 12 different numerical thresholds to define impaired kidney function that would prompt a procurement biopsy. Additionally, wide variability was seen in biopsy technique and procedures for biopsy interpretation and reporting of findings to transplant programs. These findings identify a clear opportunity for standardization of procurement biopsies to best practices.

Deceased-Donor Acute Kidney Injury and BK Polyomavirus in Kidney Transplant Recipients

BACKGROUND AND OBJECTIVES

BK polyomavirus (BKV) infection commonly complicates kidney transplantation, contributing to morbidity and allograft failure. The virus is often donor-derived and influenced by ischemia-reperfusion processes and disruption of structural allograft integrity. We hypothesized that deceased-donor AKI associates with BKV infection in recipients.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We studied 1025 kidney recipients from 801 deceased donors transplanted between 2010 and 2013, at 13 academic centers. We fitted Cox proportional-hazards models for BKV DNAemia (detectable in recipient blood by clinical PCR testing) within 1 year post-transplantation, adjusting for donor AKI and other donor- and recipient-related factors. We validated findings from this prospective cohort with analyses for graft failure attributed to BKV within the Organ Procurement and Transplantation Network (OPTN) database.

RESULTS

The multicenter cohort mean kidney donor profile index was 49±27%, and 26% of donors had AKI. Mean recipient age was 54±13 years, and 25% developed BKV DNAemia. Donor AKI was associated with lower risk for BKV DNAemia (adjusted hazard ratio, 0.53; 95% confidence interval, 0.36 to 0.79). In the OPTN database, 22,537 (25%) patients received donor AKI kidneys, and 272 (0.3%) developed graft failure from BKV. The adjusted hazard ratio for the outcome with donor AKI was 0.7 (95% confidence interval, 0.52 to 0.95).

CONCLUSIONS

In a well-characterized, multicenter cohort, contrary to our hypothesis, deceased-donor AKI independently associated with lower risk for BKV DNAemia. Within the OPTN database, donor AKI was also associated with lower risk for graft failure attributed to BKV.

PODCAST

This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2021_03_10_CJN18101120_final.mp3.

DCD Renal Transplantation From Donors With Acute Kidney Injury

BACKGROUND

Deceased donor kidneys with acute kidney injury (AKI) and donation after circulatory death (DCD) kidneys are viable sources of organs. The outcomes of renal transplantation from DCD donors with AKI are not known.

METHODS

A retrospective review of deceased donor renal transplants performed from 2006 to 2016 was conducted using the United Network for Organ Sharing dataset. Donors were stratified by DCD or brain dead status and by AKI stage. Recipients were followed until graft failure or the end of study. Cox regression was used to adjust for donor, recipient, and transplant covariates known to affect the incidence of delayed graft function and graft survival.

RESULTS

A total of 135 644 patients were included in the study. The odds of delayed graft function among DCD recipients were significantly higher across all donor AKI stages. The unadjusted risk of overall and death-censored graft failure were similar between the 2 groups. After adjusting for covariates, there was a significant increase in the risk of overall graft failure in recipients of DCD allografts from donors with stage 2 AKI. There was also a higher risk of death-censored graft failure among stage 1 and 2 AKI DCD recipients.

CONCLUSIONS

DCD renal allografts from donors experiencing stage 1 and 2 AKI have a higher adjusted risk of death-censored graft failure than AKI stage-matched donation after brain death renal allografts. Their use, however, is still associated with improved outcomes compared with waitlist mortality.

Procurement Biopsies Can Predict Unfavorable Outcomes in Kidneys With Low MAPI Score Values

BACKGROUND

There are few reports about the usefulness of Maryland Aggregate Pathology Index (MAPI) score in procurement biopsies. This study aimed to evaluate the association between histopathological analysis according to MAPI and unfavorable outcomes in the first year after kidney transplantation (KT).

METHODS

This retrospective study included deceased-donor KT patients whose grafts were biopsied before transplantation and had low MAPI scores (<8) in frozen sections (FSs). Paraffin sections (PSs) were analyzed after KT. MAPI parameters were global glomerulosclerosis in more than 15% (2 patients), periglomerular fibrosis (4 patients), wall-lumen ratio of arteries >0.5 (2 patients), arteriolar hyalinosis (4 patients), and interstitial scar (3 patients). Multivariable models were used to analyze risk factors for delayed graft function (DGF), prolonged DGF, inferior renal function, and graft loss (P < .05).

RESULTS

One hundred fifty-nine KTs were included. Donors (n = 120) were predominantly men (70%) and young adults (37.68 ± 12.50 years old) who suffered a traumatic death (55.8%). Recipients were predominantly men (62.26%) and adults (45.70 ± 15.80 years old) with kidney disease of unknown etiology (39.6%). Low rates of agreement between FS and PS were observed for all MAPI criteria, with kappa values ranging from 0.28 to 0.51. Using FS, no histologic parameter was independently associated with outcomes. After adjustment, glomerulosclerosis was an independent risk factor for prolonged DGF (odds ratio = 6.18: 95% confidence interval, 1.27-30.18) and wall-lumen ratio >0.5 for inferior renal function at 1 year (odds ratio = 4.08; 95% confidence interval, 1.21-13.76).

CONCLUSION

Procurement biopsies can be useful to predict inferior outcomes even in kidneys with low MAPI scores.

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.

Evaluation of donor kidneys prior to transplantation: an update of current and emerging methods

The lack of suitable kidney donor organs has led to rising numbers of patients with end stage renal disease waiting for kidney transplantation. Despite decades of clinical experience and research, no evaluation process that can reliably predict the outcome of an organ has yet been established. This review is an overview of current methods and emerging techniques in the field of donor kidney evaluation prior to transplantation. Established techniques like histological evaluation, clinical scores, and machine perfusion systems offer relatively reliable predictions of delayed graft function but are unable to consistently predict graft survival. Emerging techniques including molecular biomarkers, new imaging technologies, and normothermic machine perfusion offer innovative approaches toward a more global evaluation of an organ with better outcome prediction and possibly even identification of targets for therapeutic interventions prior to transplantation. These techniques should be studied in randomized controlled trials to determine whether they can be safely used in routine clinical practice to ultimately reduce the discard rate and improve graft outcomes.