Significance of preimplantation analysis of kidney biopsies from expanded criteria donors in long-term outcome

Challenges in standardizing preimplantation kidney biopsy assessments and the potential of AI-Driven solutions

PURPOSE OF REVIEW

This review explores the variability in preimplantation kidney biopsy processing methods, emphasizing their impact on histological interpretation and allocation decisions driven by biopsy findings. With the increasing use of artificial intelligence (AI) in digital pathology, it is timely to evaluate whether these advancements can overcome current challenges and improve organ allocation amidst a growing organ shortage.

RECENT FINDINGS

Significant inconsistencies exist in biopsy methodologies, including core versus wedge sampling, frozen versus paraffin-embedded processing, and variability in pathologist expertise. These differences complicate study comparisons and limit the reproducibility of histological assessments. Emerging AI-driven tools and digital pathology show potential for standardizing assessments, enhancing reproducibility, and reducing dependence on expert pathologists. However, few studies have validated their clinical utility or demonstrated their predictive performance for long-term outcomes.

SUMMARY

Novel AI-driven tools hold promise for improving the standardization and accuracy of preimplantation kidney biopsy assessments. However, their clinical application remains limited due to a lack of proven associations with posttransplant outcomes and insufficient evaluation of predictive performance metrics. Future research should prioritize longitudinal studies using large-scale datasets, rigorous validation, and comprehensive assessments of predictive performance for both short- and long-term outcomes to fully establish their clinical utility.

Postreperfusion Renal Allograft Biopsy Predicts Outcome of Single-Kidney Transplantation: A 10-Year Observational Study in China

Introduction

Biopsy findings often lead to the discard of many donor kidneys although their clinical value is not fully understood. We investigated the predictive value of postreperfusion biopsy on long-term allograft outcome after single-kidney transplantation.

Methods

We retrospectively evaluated the significance of histologic findings, read by experienced renal pathologists, in 461 postreperfusion biopsy specimens collected from 2010 to 2017 after deceased donor renal transplant; and performed time-to-event analyses to determine the association between histology and hazard of death-censored graft failure. Recipients were followed-up with over a median time of 6.8 (range, 0.2-11.9) years. We assessed specimens using the Remuzzi score (scale of 0-12) and categorized them into low-score (≤3) and high-score (>3) groups. Kappa coefficients were calculated to assess agreement in procurement versus reperfusion biopsies.

Results

High Remuzzi score kidneys came from older donors with a higher incidence of hypertension, higher final creatinine, death from cerebrovascular disease, expanded criteria donor, and a higher kidney donor risk index (KDRI) (all P < 0.001). In adjusted analyses, Remuzzi score was independently associated with death-censored graft failure (hazard ratio [HR] 1.389 for each 1 score rise in Remuzzi score, 95% confidence interval 1.181-1.633, P < 0.001). Overall histologic agreement (procurement biopsy versus reperfusion biopsy) was kappa = 0.137.

Conclusion

Our findings suggest that postreperfusion biopsy is associated with long-time graft outcomes after transplant from a deceased donor. Agreement between procurement and reperfusion biopsy was found to be low. Prospective trials are necessary to optimize procurement biopsy practices.

Performance of Scores Predicting Adverse Outcomes in Procurement Kidney Biopsies From Deceased Donors With Organs of Lower-Than-Average Quality

Several scores have been devised for providing a prognosis of outcomes after kidney transplantation. This study is a comprehensive test of these scores in a cohort of deceased donors with kidneys of lower-than-average quality and procurement biopsies. In total, 15 scores were tested on a retrospective cohort consisting of 221 donors, 223 procurement biopsies, and 223 recipient records for performance on delayed graft function, graft function, or death-censored graft loss. The best-performing score for DGF was the purely clinical Chapal score (AUC 0.709), followed by the Irish score (AUC 0.684); for graft function, the Nyberg score; and for transplant loss, the Snoeijs score (AUC 0.630) and the Leuven scores (AUCs 0.637 and 0.620). The only score with an acceptable performance was the Chapal score. Its disadvantage is that knowledge of the cold ischemia time is required, which is not known at allocation. None of the other scores performed acceptably. The scores fared better in discarded kidneys than in transplanted kidneys. Our study shows an unmet need for practical prognostic scores useful at the time of a decision about discarding or accepting deceased donor kidneys of lower-than-average quality in the Eurotransplant consortium.

Progress in Pathological Diagnosis after Kidney Transplantation: Current Trend and Future Perspective

Advances in immunosuppressive therapy; posttransplant management of allograft rejection; and measures against infectious diseases, cardiovascular diseases, and malignancy dramatically improved graft and patient survival after kidney transplantation (KT). Among them, kidney allograft biopsy is an important tool and the gold standard for the diagnosis of various kidney allograft injuries, including allograft rejection, virus-induced nephropathy, calcineurin inhibitor toxicity, and posttransplant glomerular diseases. The Banff Conference on Allograft Pathology has contributed to establishing the diagnostic criteria for kidney allograft rejection and polyomavirus-associated nephropathy that are used as a common standard worldwide. In addition to the for-cause biopsy, many transplant centers perform protocol biopsies in the early and late posttransplant periods to detect and treat allograft injury earlier. Preimplantation biopsy in deceased-donor KT has also been performed, especially in the marginal donor, and attempts have been made to predict the prognosis in combination with clinical information and the renal resistance of hypothermic machine perfusion. Regarding the preimplantation biopsy from a living kidney donor, it can provide useful information on aging and/or early changes in lifestyle diseases, such as glomerulosclerosis, tubulointerstitial changes, and arterial and arteriolar sclerosis, and be used as a reference for the subsequent management of living donors. In this review, morphologic features of important kidney allograft pathology, such as allograft rejection and polyomavirus-associated nephropathy, according to the latest Banff classification and additional information derived from protocol biopsy, and future perspectives with recently developed technologies are discussed.

Disparities in Deceased Donor Kidney Offer Acceptance: A Survey of Canadian Transplant Nephrologists, General Surgeons and Urologists

Background

Significant variability in organ acceptance thresholds have been demonstrated across the United States, but data regarding the rate and rationale for kidney donor organ decline in Canada are lacking.

Objective

To examine decision making regarding deceased kidney donor acceptance and non-acceptance in a population of Canadian transplant professionals.

Design

A survey study of theoretical deceased donor kidney cases of increasing complexity.

Setting

Canadian transplant nephrologists, urologists, and surgeons making donor call decisions responding to an electronic survey between July 22 and October 4, 2022.

Participants

Invitations to participate were distributed to 179 Canadian transplant nephrologists, surgeons, and urologists through e-mail. Participants were identified by contacting each transplant program and requesting a list of physicians who take donor call.

Measurements

Survey respondents were asked whether they would accept or decline a given donor, assuming there was a suitable recipient. They were also asked to cite reasons for donor non-acceptance.

Methods

Donor scenario-specific acceptance rates (total acceptance divided by total number of respondents for a given scenario and overall) and reasons for decline were determined and presented as a percentage of the total cases declined.

Results

In all, 72 respondents from 7 provinces completed at least one question of the survey, with considerable variability between acceptance rates for centers; the most conservative center declined 60.9% of donor cases, whereas the most aggressive center declined only 28.1%, P-value < .001. There was an increased risk of non-acceptance with advancing age, donation after cardiac death, acute kidney injury, chronic kidney disease, and comorbidities.

Limitations

As with any survey, there is the potential for participation bias. In addition, this study examines donor characteristics in isolation, however, asks respondent to assume there is a suitable candidate available. In reality, whenever donor quality is considered, it should be considered in the context of the intended recipient.

Conclusion

In a survey of increasingly medically complex deceased kidney donor cases, there was significant variability in donor decline among Canadian transplant specialists. Given relatively high rates of donor decline and apparent heterogeneity in acceptance decisions, Canadian transplant specialists may benefit from additional education regarding the benefits achieved from even medically complex kidney donors for appropriate candidates relative to remaining on dialysis on the transplant waitlist.

Effect of creatinine metrics on outcome after transplantation of marginal donor kidneys

INTRODUCTION

Predicting outcome after transplantation of marginal kidneys is a challenging task. Donor creatinine or estimated glomerular filtration rate (eGFR) are integral components of the respective risk scores. However, there is uncertainty on which of their values obtained successively during procurement is the most suitable.

MATERIAL AND METHODS

This is a retrospective study of 221 adult brain death donors with marginal kidneys, transplanted in 223 recipients. We applied logistic regression analysis to investigate the association between initial (at hospital admission), nadir (lowest), zenith (highest) and terminal (at recovery) donor eGFR with primary non-function (PNF), delayed graft function (DGF), 3- and 12-month graft function and 1- and 3-year patient- and death-censored graft survival.

RESULTS

In the multivariate analysis, admission, terminal, and the lowest donor eGFR could most accurately predict DGF. The respective ORs [95% CI] were: 0.875 [0.771-0.993], 0.818 [95% CI: 0.726-0.922] and 0.793 [0.689-0.900]. Although not being significant for DGF (OR 0.931 [95% CI: 0.817-1.106]), the highest eGFR was the best predictor of 3-month graft function (adjusted b coefficient 1.161 [95% CI: 0.355-1.968]). Analysis of primary nonfunction showed that determination of initial and the highest eGFR proved to be the best predictors. The respective ORs [95% CI] were: 0.804 [0.667-0.968] and 0.750 [0.611-0.919]. There were no differences in the risk associations of each of the four eGFR recordings with patient- and graft survival.

CONCLUSION

The various eGFR recordings determined during the procurement process of marginal donors can predict PNF, DGF and 3- and 12-month graft function. Regarding short-term patient- and graft survival, there appears to be impacted by recipient factors rather than donor kidney function.

Evaluation of Expanded Criteria Donors Using the Kidney Donor Profile Index and the Preimplantation Renal Biopsy

The increasing comorbidity of kidney transplant (KT) donors make it necessary to develop scores to correctly assess the quality of kidney grafts. This study analyzes the usefulness of the preimplantation biopsy and the Kidney Donor Profile Index (KDPI) as indicators of KT survival from expanded criteria donors (ECD). Retrospective study of KT in our center between January 2010 to June 2019 who received a kidney from an ECD and underwent a preimplantation biopsy. 266 KT were included. Graft survival was categorized by KDPI quartiles: Q1 = 86%, Q2 = 95%, Q3 = 99% and Q4 = 100%. KT from KDPI Q1 presented better survival (p = 0.003) and Q4 donors had worse renal function (p = 0.018) and poorer glomerular filtration rate (3rd month; p = 0.017, 1st year; p = 0.010). KT survival was analyzed according to KDPI quartile and preimplantation biopsy score simultaneously: Q1 donors with biopsy score ≤3 had the best survival, especially comparing against Q3 with a biopsy score >3 and Q4 donors (p = 0.014). In multivariable analysis, hyaline arteriopathy, glomerulosclerosis, and KDPI Q4 were predictors for graft survival. High KDPI and a greater histological injury in the preimplantation biopsy, especially glomerular and vascular lesions, were related to a higher rate of KT loss from ECD.

Deep learning identified pathological abnormalities predictive of graft loss in kidney transplant biopsies

Interstitial fibrosis, tubular atrophy, and inflammation are major contributors to kidney allograft failure. Here we sought an objective, quantitative pathological assessment of these lesions to improve predictive utility and constructed a deep-learning-based pipeline recognizing normal vs. abnormal kidney tissue compartments and mononuclear leukocyte infiltrates. Periodic acid- Schiff stained slides of transplant biopsies (60 training and 33 testing) were used to quantify pathological lesions specific for interstitium, tubules and mononuclear leukocyte infiltration. The pipeline was applied to the whole slide images from 789 transplant biopsies (478 baseline [pre-implantation] and 311 post-transplant 12-month protocol biopsies) in two independent cohorts (GoCAR: 404 patients, AUSCAD: 212 patients) of transplant recipients to correlate composite lesion features with graft loss. Our model accurately recognized kidney tissue compartments and mononuclear leukocytes. The digital features significantly correlated with revised Banff 2007 scores but were more sensitive to subtle pathological changes below the thresholds in the Banff scores. The Interstitial and Tubular Abnormality Score (ITAS) in baseline samples was highly predictive of one-year graft loss, while a Composite Damage Score in 12-month post-transplant protocol biopsies predicted later graft loss. ITASs and Composite Damage Scores outperformed Banff scores or clinical predictors with superior graft loss prediction accuracy. High/intermediate risk groups stratified by ITASs or Composite Damage Scores also demonstrated significantly higher incidence of estimated glomerular filtration rate decline and subsequent graft damage. Thus, our deep-learning approach accurately detected and quantified pathological lesions from baseline or post-transplant biopsies and demonstrated superior ability for prediction of post-transplant graft loss with potential application as a prevention, risk stratification or monitoring tool.

Impact of pre-transplant biopsy on 5-year outcomes of expanded criteria donor kidney transplantation

AIM

Compared to Standard Criteria Donors (SCD), Expanded Criteria Donor (ECD) kidneys are associated with poorer outcomes, although pre-transplant biopsy may mitigate risks. This study assessed 5-year outcomes of deceased-donor kidney transplant recipients, comparing recipients of ECD allografts evaluated histologically to recipients of SCD and ECD kidneys assessed clinically.

METHODS

This is a single-centre retrospective study. From November 2005 to December 2009 (Era 1), donors were assessed clinically for suitability for kidney donation. From December 2009 to October 2017 (Era 2), kidneys from ECDs and diabetics underwent pre-transplant biopsy and were allocated based on Remuzzi score. Outcomes of Era 1 and 2 recipients were compared.

RESULTS

ECD kidney transplantation increased from 30.4% to 40.0% from Era 1 to 2. Univariable Cox regression, stratified by transplant era, found that 5-year graft loss was highest with Era 1 ECD (HR 2.5, 95% CI 1.1-5.5, P = .027) while graft loss for Era 2 ECD recipients was similar to SCD recipients. There was no difference in 5-year recipient survival. Amongst Era 1 ECD recipients, 51.2% experienced rejection compared to 30.8-41.5% for other subgroups. Five-year eGFR was higher with Era 2 ECD at 48.4 (33.3-60.7) ml/min/1.73 m² compared to 42.2 (35.8-57.3) ml/min/1.73 m² for Era 1 ECD. However, these differences were not statistically significant.

CONCLUSION

Introduction of pre-transplant biopsy assessment may be associated with improved outcomes of ECD kidney recipients such that they are now comparable to SCD kidney recipients, with benefits persisting over 5 years.

Reproducibility of Deceased Donor Kidney Procurement Biopsies

BACKGROUND AND OBJECTIVES

Unfavorable histology on procurement biopsies is the most common reason for deceased donor kidney discard. We sought to assess the reproducibility of procurement biopsy findings.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We compiled a continuous cohort of deceased donor kidneys transplanted at our institution from 1/1/2006 to 12/31/2016 that had at least one procurement biopsy performed, and excluded cases with missing biopsy reports and those used in multiorgan transplants. Suboptimal histology was defined as the presence of advanced sclerosis in greater than or equal to one biopsy compartment (glomeruli, tubules/interstitium, vessels). We calculated κ coefficients to assess agreement in optimal versus suboptimal classification between sequential biopsy reports for kidneys that underwent multiple procurement biopsies and used time-to-event analysis to evaluate the association between first versus second biopsies and patient and allograft survival.

RESULTS

Of the 1011 kidneys included in our cohort, 606 (60%) had multiple procurement biopsies; 98% had first biopsy performed at another organ procurement organization and their second biopsy performed locally. Categorical agreement was highest for vascular disease (κ=0.17) followed by interstitial fibrosis and tubular atrophy (κ=0.12) and glomerulosclerosis (κ=0.12). Overall histologic agreement (optimal versus suboptimal) was κ=0.15. First biopsy histology had no association with allograft survival in unadjusted or adjusted analyses. However, second biopsy optimal histology was associated with a higher probability of death-censored allograft survival, even after adjusting for donor and recipient factors (adjusted hazard ratio, 0.50; 95% confidence interval, 0.34 to 0.75; P=0.001).

CONCLUSIONS

Deceased donor kidneys that underwent multiple procurement biopsies often displayed substantial differences in histologic categorization in sequential biopsies, and there was no association between first biopsy findings and post-transplant outcomes.

To discard or not to discard: transplantation and the art of scoring

The growing gap between inadequate supply and constantly high demand for kidney transplantation observed in the last two decades led to exploring the possibility of using organs from older donors with an increasing number of comorbidities. The main issue in this scenario is to identify transplantable organs and to allocate them to the most suitable recipients. A great number of clinical investigations proposed several acceptance/allocation criteria to reduce the discard rate of these kidneys and to improve their outcome, including histological features at the time of transplant. Despite the widespread use of several histological scoring systems, there is no consensus on their value in predicting allograft survival and there is established evidence that histological analysis is the most common reason to discard expanded criteria donor kidneys. To overcome this issue, a clinical scoring system, the Kidney Donor Profile Index (KDPI), was developed on the basis of easily accessible donor features. The KDPI score, adopted in the new US allocation procedure, has good reproducibility but presents several limitations, as suggested also in this issue of Clinical Kidney Journal. This observation should stimulate the search for novel scores combining clinical, histological and molecular features in an attempt to improve the decision process.

Renal transplants from older deceased donors: Is pre-implantation biopsy useful? A monocentric observational clinical study

AIM

To compare survival of kidney transplants from deceased extended criteria donors (ECD) according to: (1) donor graft histological score; and (2) allocation of high score grafts either to single (SKT) or dual (DKT) transplant.

METHODS

Renal biopsy was performed as part of either a newly adopted DKT protocol, or of surveillance protocol in the past. A total 185 ECD graft recipients were categorized according to pre-implantation graft biopsy into 3 groups: SKT with graft score 1 to 4 [SKT_(1-4), n = 102]; SKT with donor graft score 5 to 8 [SKT_{(> 4)}, n = 30]; DKT with donor graft score 5 to 7 (DKT, n = 53). Graft and patient survival were analyzed by Kaplan-Meier curves and compared by log-rank test. Mean number of functioning graft years by transplant reference, and mean number of dialysis-free life years by donor reference in recipients were also calculated at 1, 3 and 6 years from transplantation.

RESULTS

There were no statistically significant differences in graft and patient survival between SKT_(1-4) and SKT_{(> 4)}, and between SKT_{(> 4)} and DKT. Recipient renal function (plasma creatinine and creatinine clearance) at 1 years did not differ in SKT_(1-4) and SKT_{(> 4)} (plasma creatinine 1.71 ± 0.69 and 1.69 ± 0.63 mg/dL; creatinine clearance 49.6 + 18.5 and 52.6 + 18.8 mL/min, respectively); DKT showed statistically lower plasma creatinine (1.46 ± 0.57, P < 0.04) but not different creatinine clearance (55.4 + 20.4). Due to older donor age in the DKT group, comparisons were repeated in transplants from donors older than 70 years, and equal graft and patient survival in SKT and DKT were confirmed. Total mean number of functioning graft years by transplant reference at 1, 3 and 6 post-transplant years were equal between the groups, but mean number of dialysis-free life years by donor reference were significantly higher in SKT (mean difference compared to DKT at 6 years: 292 [IQR 260-318] years/100 donors in SKT_(1-4) and 292.5 [(IQR 247.8-331.6) in SKT_{(> 4)}].

CONCLUSION

In transplants from clinically suitable ECD donors, graft survival was similar irrespective of pre-implantation biopsy score and of allocation to SKT or DKT. These results suggest use of caution in the use of histology as the only decision criteria for ECD organ allocation.

Histopathological evaluation of pretransplant donor biopsies in expanded criteria donors with high kidney donor profile index: a retrospective observational cohort study

There is no consensus on the allocation of renal transplants from expanded criteria donors (ECD). The Kidney Donor Profile Index (KDPI) is used without the need for pretransplant donor biopsies (PTDB). We explored whether PTDB based on Remuzzi Score (RS) allows identification of those marginal kidneys in the highest calculated KDPI risk group (>91%) that appropriate for single transplantation. A retrospective study was conducted of 485 consecutive kidneys procured from a single center and transplanted if the RS was ≤4. We compared 5-year kidney and patients survival between KDPI groups and between RS <4 or =4 in the highest KDPI group. The median KDPI (interquartile range) was 71 (66-76) for KDPI <80% (n = 77), 86 (81-90) for KDPI 81-90% (n = 82), and 97 (94-100) for KDPI >91% (n = 205). Patient survival at 5 years was 85.7%, 85.3%, and 76.09% (P = 0.058) and death-censored graft survival was 84.4%, 86.5%, 73.6% (P = 0.015), respectively for each KDPI group. In >91% calculated KDPI group, there were no differences in graft survival depending on the RS (<4 vs. =4) (P = 0.714). The implementation of PTDB based on RS used for allocation of organs with the highest KDPI range could support to the acceptance of suitable organs for single transplantation with good patient and graft survival rate.

Strategies for an Expanded Use of Kidneys From Elderly Donors

The old-for-old allocation policy used for kidney transplantation (KT) has confirmed the survival benefit compared to remaining listed on dialysis. Shortage of standard donors has stimulated the development of strategies aimed to expand acceptance criteria, particularly of kidneys from elderly donors. We have systematically reviewed the literature on those different strategies. In addition to the review of outcomes of expanded criteria donor or advanced age kidneys, we assessed the value of the Kidney Donor Profile Index policy, preimplantation biopsy, dual KT, machine perfusion and special immunosuppressive protocols. Survival and functional outcomes achieved with expanded criteria donor, high Kidney Donor Profile Index or advanced age kidneys are poorer than those with standard ones. Outcomes using advanced age brain-dead or cardiac-dead donor kidneys are similar. Preimplantation biopsies and related scores have been useful to predict function, but their applicability to transplant or refuse a kidney graft has probably been overestimated. Machine perfusion techniques have decreased delayed graft function and could improve graft survival. Investing 2 kidneys in 1 recipient does not make sense when a single KT would be enough, particularly in elderly recipients. Tailored immunosuppression when transplanting an old kidney may be useful, but no formal trials are available.Old donors constitute an enormous source of useful kidneys, but their retrieval in many countries is infrequent. The assumption of limited but precious functional expectancy for an old kidney and substantial reduction of discard rates should be generalized to mitigate these limitations.

Clinical value of pathologic examination of non-neoplastic kidney in patients with upper urinary tract malignancies

BACKGROUND/AIMS

While surgical resection remains the standard of care in the treatment of upper urinary tract malignancies, nephrectomy is a risk factor for the development of chronic kidney disease (CKD). The aim of this study was to determine whether histologic evaluation of non-neoplastic kidney could enable early identification of unrecognized kidney disease and could be of prognostic value in predicting postoperative renal outcomes.

METHODS

We retrospectively analyzed 51 patients with upper urinary tract malignancies who received uninephrectomy or uninephroureterectomy. A thorough pathologic evaluation of non-neoplastic kidney including special stains, immunofluorescence, and electron microscopic studies was performed. The degree of parenchymal changes was graded from 0 to 15.

RESULTS

Of 51 patients, only 13 showed normal kidney pathology. Fifteen patients showed glomerular abnormalities, 14 showed diabetic nephropathy, and 11 showed vascular nephropathy. There was one case each of reflux nephropathy and chronic pyelonephritis. The median histologic score was 5 points. Only 25.4% of patients had ≤ 3 points. Score more than 5 was observed in 47.1% of patients. Postoperative estimated glomerular filtration rate (eGFR) at 3 to 36 months were obtained from 90.2% of patients, and of those, 34.8% had de novo CKD. Since no one had CKD in partial nephrectomized patients, we determined risk factors for CKD in radical nephrectomized patients. Cox regression analysis revealed that postoperative AKI, preoperative eGFR, and histologic score of non-neoplastic kidney were the independent predictors for CKD.

CONCLUSIONS

We conclude that routine pathologic evaluation of non-neoplastic kidney provides valuable diagnostic and prognostic information.

Recommendations for donation after circulatory death kidney transplantation in Europe

Donation after circulatory death (DCD) donors provides an invaluable source for kidneys for transplantation. Over the last decade, we have observed a substantial increase in the number of DCD kidneys, particularly within Europe. We provide an overview of risk factors associated with DCD kidney function and survival and formulate recommendations from the sixth international conference on organ donation in Paris, for best-practice guidelines. A systematic review of the literature was performed using Ovid Medline, Embase and Cochrane databases. Topics are discussed, including donor selection, organ procurement, organ preservation, recipient selection and transplant management.

The Donor Kidney Biopsy and Its Implications in Predicting Graft Outcomes: A Systematic Review

Despite a growing organ shortage in the United States, many deceased donor kidneys removed for transplantation are discarded. Kidney biopsy findings often play a role in these discards, although it is not clear whether biopsies reliably inform acceptance decisions. Therefore, we carried out a systematic review of the medical literature on the utility of both procurement and implantation biopsies for predicting posttransplant outcomes. Between January 1, 1994 and July 1, 2014, 47 studies were published in the English language literature that examined the association between pretransplant donor biopsy findings from 50 or more donors (with more than half being from deceased donors) and either posttransplant graft failure, delayed graft function, or graft function. In general, study quality was poor. All were retrospective or did not indicate if they were prospective. Results were heterogeneous, with authors as often as not concluding that biopsy results did not predict posttransplant outcomes. The percent glomerular sclerosis was most often examined, and failed to predict graft failure in 7 of 14 studies. Of 15 semiquantitative scoring systems proposed, none consistently predicted posttransplant outcomes across studies. Routine use of biopsies to help determine whether or not to transplant a kidney should be reexamined.

The Kidney Donor Profile Index (KDPI) of marginal donors allocated by standardized pretransplant donor biopsy assessment: distribution and association with graft outcomes

Pretransplant donor biopsy (PTDB)-based marginal donor allocation systems to single or dual renal transplantation could increase the use of organs with Kidney Donor Profile Index (KDPI) in the highest range (e.g. >80 or >90), whose discard rate approximates 50% in the United States. To test this hypothesis, we retrospectively calculated the KDPI and analyzed the outcomes of 442 marginal kidney transplants (340 single transplants: 278 with a PTDB Remuzzi score<4 [median KDPI: 87; interquartile range (IQR): 78-94] and 62 with a score=4 [median KDPI: 87; IQR: 76-93]; 102 dual transplants [median KDPI: 93; IQR: 86-96]) and 248 single standard transplant controls (median KDPI: 36; IQR: 18-51). PTDB-based allocation of marginal grafts led to a limited discard rate of 15% for kidneys with KDPI of 80-90 and of 37% for kidneys with a KDPI of 91-100. Although 1-year estimated GFRs were significantly lower in recipients of marginal kidneys (-9.3, -17.9 and -18.8 mL/min, for dual transplants, single kidneys with PTDB score<4 and =4, respectively; p<0.001), graft survival (median follow-up 3.3 years) was similar between marginal and standard kidney transplants (hazard ratio: 1.20 [95% confidence interval: 0.80-1.79; p=0.38]). In conclusion, PTDB-based allocation allows the safe transplantation of kidneys with KDPI in the highest range that may otherwise be discarded.

Spanish consensus document for acceptance and rejection of kidneys from expanded criteria donors

In the recent years, more than 60% of available deceased donors are either older than 50 yr or have significant vascular comorbidities. This makes the acceptance and rejection criteria of renal allografts very rigorous, especially in cases of younger recipients, and at the same time encourages live donations. In our country, there is a lack of homogeneity in the percentages of use of expanded criteria donor (ECD) allografts between the different autonomous communities. Furthermore, the criteria vary greatly, and in some cases, great importance is given to the biopsy while in others very little. In this study, we present a unified and homogenous criteria agreed upon by consensus of a 10-member Panel representing major scientific societies related to renal transplantation in Spain. The criteria are to be used in accepting and/or rejecting kidneys from the so-called ECDs. The goal was to standardize the use of these organs, to optimize the results, and most importantly to provide for the maximum well being of our patients. Finally, we believe that after taking into account the Panel's thorough review of specific scientific literature, this document will be adaptable to other national renal transplant programmes.

The marginal kidney donor

PURPOSE OF REVIEW

The current era of organ shortage has necessitated a widening of criteria for donation, considering donors who would have been considered unsuitable before. This review summarizes the recent advances in strategies to maximize the use of marginal kidneys without compromising the outcomes.

RECENT FINDINGS

Various strategies have been studied and implemented to optimize procurement and allocation of marginal kidneys, and to preserve their function. In particular, a growing number of transplant centers are using donors after circulatory death. Whereas normothermic ex-vivo and postmortem perfusion are promising procedures to improve the outcomes of marginal grafts in the future, dual-kidney transplantation is a viable approach which is at present potentially underutilized. Despite active research on new strategies to evaluate organ quality, pretransplant biopsy assessment currently remains the most reliable method. The practice of using living donors with advanced age is supported by available evidence, whereas the use of young living donors with minor medical abnormalities needs further investigation.

SUMMARY

Progress has been made in the recent years, clarifying the best criteria for evaluating, recovering, and allocating marginal kidney donors. However, further research is needed, with special regards to the criteria for using marginal living-kidney donors.

Outcomes in renal transplantation with expanded-criteria donors

BACKGROUND

Kidney transplantation is the treatment of choice for patients with end-stage renal disease. In recent years donor criteria have changed to increase the percentage of expanded-criteria donors (ECDs). The aim of this study was to analyze transplants from ECDs obtained at our institution from. 2010 to 2012. We studied the comorbidity of ECD, preimplantation histologic study, renal function, and survival of transplanted grafts.

PATIENTS AND METHODS

Eighty ECDs (160 kidneys) were analyzed. Forty-nine grafts were not implanted owing to macroscopic lesions (37 kidneys) or histologic findings on preimplantation biopsy (12 kidneys). Finally, 60 grafts from ECDs were implanted in our center. We analyzed the characteristics of the grafts (kidney function, creatinine clearance) and compared the data with a control group of allografts from standard-criteria donors (n = 14).

RESULTS

The median age of the ECD group was 72 years (range 65-77). No differences were found in certain characteristics between the ECDs whose kidneys were or were not implanted (hypertension, diabetes, creatinine at the time of the donation or proteinuria). However, there were differences in donor age (75 vs 67; P = .043), increased preimplantation biopsy score (6.8 ± 1.3 vs 4.8 ± 1.1; P = .041), and a higher percentage of cardiovascular disease (62.5% vs 43%; P = .038). Comparison of ECD and non-ECD grafts showed a lower creatinine clearance at 1 year (50 ± 05 mL/min vs 69 ± 96 mL/min, respectively; P < .001) and 2 years (50 ± 07 mL/min vs 67 ± 74 mL/min; P < .001) after transplantation. There were no differences in delayed graft function or graft survival between the 2 groups at 2 years after transplantation (95% vs 100%; P = .38).

CONCLUSIONS

We found no differences in graft survival from ECD compared with the control group of standard-criteria donors. The evaluation of grafts from ECD may be a strategy to increase the number of kidney transplants.

Pre-implant biopsy predicts outcome of single-kidney transplantation independent of clinical donor variables

BACKGROUND

Pre-implant biopsy findings account for the discard of many donor kidneys although their clinical value is not fully understood. We retrospectively investigated the predictive value of pre-implant histology, which in our center was obtained for protocol purposes, not for transplant decisions, on long-term allograft and recipient outcome after single-kidney transplantation.

METHODS

This single-center study included 628 consecutive adult recipients of 174 Expanded Criteria Donor (ECD) and 454 Standard Criteria Donor kidneys. Chronic donor organ injury was assessed applying a chronic lesion score differentiating between mild, moderate, and severe histologic organ injury based on the integration of glomerular, vascular, tubular, and interstitial lesions. Recipients were followed over a median time of 7.8 years.

RESULTS

Donor kidneys exhibiting mild or moderate chronic lesions yielded almost identical graft and recipient survival independent of ECD status or other clinical covariables (HR 1.20, 95% CI 0.83-1.74, P=0.326, and HR 1.27, 95% CI 0.83-1.95, P=0.274, respectively). However, if allograft injury was severe, occurring in 3% of transplanted kidneys, graft and recipient survival was significantly reduced (HR 3.13, 95% CI 1.61-6.07, P<0.001 and HR 2.42, 95% CI 1.16-5.04, P=0.005, respectively).

CONCLUSION

The results suggest that donor kidneys displaying moderate chronic injury can safely be transplanted as single kidneys, while organs displaying severe injury should be discarded. Thus, pre-implant biopsy might offer an effective approach to increase the utilization of renal donor organs, especially from ECD and donors with cerebrovascular accident as cause of death, and to improve overall graft outcome.

The role of procurement biopsies in acceptance decisions for kidneys retrieved for transplant

BACKGROUND AND OBJECTIVES

There is a shortage of kidneys for transplant, and many patients on the deceased donor kidney transplant waiting list would likely benefit from kidneys that are currently being discarded. In the United States, the most common reason given for discarding kidneys retrieved for transplant is procurement biopsy results. This study aimed to compare biopsy results from discarded kidneys with discard attributed to biopsy findings, with biopsy results from comparable kidneys that were successfully transplanted.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In this retrospective, observational, case-control study, biopsy reports were examined from 83 kidneys discarded in 2010 due to biopsy findings (cases), 83 contralateral transplanted kidneys from the same donor (contralateral controls), and 83 deceased donors randomly matched to cases by donor risk profile (randomly matched controls). A second procurement biopsy was obtained in 64 of 332 kidneys (19.3%).

RESULTS

The quality of biopsy reports was low, with amounts of tubular atrophy, interstitial inflammation, arteriolar hyalinosis, and acute tubular necrosis often not indicated; 69% were wedge biopsies and 94% used frozen tissue. The correlation between first and second procurement biopsies was poor; only 25% of the variability (R(2)) in glomerulosclerosis was explained by biopsies being from the same kidney. The percentages of glomerulosclerosis overlapped substantially between cases, contralateral controls, and randomly matched controls: 17.1%±15.3%, 9.0%±6.6%, and 5.0%±5.9%, respectively. Of all biopsy findings, only glomerulosclerosis>20% was independently correlated with discard (cases versus contralateral controls; odds ratio, 15.09; 95% confidence interval, 2.47 to 92.41; P=0.003), suggesting that only this biopsy result was used in acceptance decisions. One-year graft survival was 79.5% and 90.7% in contralateral and randomly matched controls, respectively, versus 91.6% among all deceased donor transplants in the Scientific Registry of Transplant Recipients.

CONCLUSIONS

Routine use of biopsies could lead to unnecessary kidney discards.

Kidney donor risk index is a good prognostic tool for graft outcomes in deceased donor kidney transplantation with short, cold ischemic time

BACKGROUND

We performed a retrospective cohort study to determine the prognostic value of standard criteria donor/expanded criteria donor (SCD/ECD) designation, with regard to one-yr GFR and graft survival rate, in a region with short, cold ischemic time (CIT), and how this designation compares with the kidney donor risk index (KDRI) and zero-time kidney biopsies.

METHODS

We reviewed 362 cases of deceased donor kidney transplantation (DDKT). Donor kidneys were classified as SCD or ECD. They were also assessed by the KDRI. Zero-time kidney biopsy was performed in 196 patients, and histologic score was assessed.

RESULTS

Median follow-up duration was 46 months. Forty-two cases (11.6%) used ECD kidneys. The mean CIT was only 4.9 ± 2.7 h. Graft survival rates were not significantly different between ECD and SCD groups. The KDRI showed the best correlation with one-yr estimations of glomerular filtration rate (eGFR) (R(2) = 0.230, p < 0.001), and higher KDRI was associated with a higher risk of graft failure (hazard ratio 2.63, 95% confidence interval 1.01-6.87). However, higher histologic score was not associated with a higher risk of graft failure.

CONCLUSION

KDRI has greater predictive value for short-term outcomes in DDKT with short CIT than the SCD/ECD designation or pathology.

The reproducibility and predictive value on outcome of renal biopsies from expanded criteria donors

Reproducibility and predictive value on outcome are the main criteria to evaluate the utility of histological scores. Here we analyze the reproducibility of donor biopsy assessment by different on-call pathologists and the retrospective evaluation by a single renal pathologist blinded to clinical outcomes. We also evaluate the predictive value on graft outcome of both evaluations. A biopsy was performed in donors with any of the following: age≥55 years, hypertension, diabetes, creatinine>1.5 mg/dl, or stroke. Glomerulosclerosis, interstitial fibrosis, tubular atrophy, intimal thickening, and arteriolar hyalinosis evaluated according to the Banff criteria were added to obtain a chronic score. Biopsies were classified as mild (≥3), intermediate (4-5), or advanced (6-7) damage, and unacceptable (≥8) for transplantation of 127 kidneys biopsied. Weighted κ value between both readings was 0.41 (95% CI: 0.28-0.54). Evaluation of biopsies by the renal pathologist was significantly and independently associated with estimated 12-month glomerular filtration rate and a significant composite outcome variable, including death-censored graft survival and time to reach an estimated glomerular filtration rate<30 ml/min per 1.73 m2. Thus, there was no association between readings of on-call pathologists and outcome. The lack of association between histological scores obtained by the on-call pathologists and graft outcome suggests that a specific training on renal pathology is recommended to optimize the use of kidneys retrieved from expanded criteria donors.

Assessment of donor biopsies

PURPOSE OF REVIEW

To provide an up-to-date overview about the assessment of donor biopsies and to discuss the current problems and chances of preimplantation biopsies for transplant allocation with a focus on the technical work up and the histological variables scored.

RECENT FINDINGS

Preimplantation biopsy results are the major reason for discarding procured extended donor criteria kidneys in the USA. There is neither a consensus on the work up, nor the reporting of preimplantation donor biopsies, nor the importance of the biopsy findings in the process of allocation. The best available data have been collected in the context of single vs. double kidney transplantation. A clinical risk factor score may help to define kidneys when a preimplantation biopsy is warranted. Punch biopsies using a skin punch device appear to be a reasonable alternative for surgeons fearing needle biopsies.

SUMMARY

Donor biopsies are very useful as zero-hour biopsies establishing baseline information for comparison with subsequent transplant biopsies. As none of the histological variables and scores provides perfect prediction, preimplantation biopsy results have to be interpreted in the context of all available donor and recipient information.