Zero-Time Renal Transplant Biopsies: A Comprehensive Review. Transplantation. 2016;100:1425-1439. [PMID: 26599490 DOI: 10.1097/tp.0000000000001018]

A Machine Learning-Driven Virtual Biopsy System For Kidney Transplant Patients

In kidney transplantation, day-zero biopsies are used to assess organ quality and discriminate between donor-inherited lesions and those acquired post-transplantation. However, many centers do not perform such biopsies since they are invasive, costly and may delay the transplant procedure. We aim to generate a non-invasive virtual biopsy system using routinely collected donor parameters. Using 14,032 day-zero kidney biopsies from 17 international centers, we develop a virtual biopsy system. 11 basic donor parameters are used to predict four Banff kidney lesions: arteriosclerosis, arteriolar hyalinosis, interstitial fibrosis and tubular atrophy, and the percentage of renal sclerotic glomeruli. Six machine learning models are aggregated into an ensemble model. The virtual biopsy system shows good performance in the internal and external validation sets. We confirm the generalizability of the system in various scenarios. This system could assist physicians in assessing organ quality, optimizing allograft allocation together with discriminating between donor derived and acquired lesions post-transplantation.

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.

The effect of late-onset CMV infection on the outcome of renal allograft considering initial graft function

BACKGROUND

Delayed graft function (DGF) increases the renal allograft failure risk. Late-onset Cytomegalovirus (CMV) infection's effect on the association between DGF and allograft failure has not been determined.

METHODS

In this retrospective cohort, we included all renal allograft recipients at London Health Sciences Centre from January 1, 2014 to December 30, 2017, and continued clinical follow-up until February 28, 2020. We determined whether late-onset CMV infection affects the association between DGF and allograft failure in stratified and Cox proportional hazard analyses.

RESULTS

Of 384 patients (median age [interquartile range]: 55 [43.3-63]; 38.7% female), 57 recipients (14.8%) were diagnosed with DGF. Patients with DGF were at a greater risk of CMV infection than patients without DGF (22.8% vs. 11.3%, p = .017). Late-onset CMV infection (odds ratio [OR]: 4.7, 95% CI: 2.07-10.68) and rejection (OR: 9.59, 95% CI: 4.15-22.16) significantly increased the risk of allograft failure in recipients with DGF. Patients with DGF had a significantly greater risk of graft failure than those without DGF (17.5% vs. 6.1%, p = .007). In the adjusted Cox hazard model, CMV infection significantly increased the risk of allograft failure (aHR: 3.19, 95% CI: 1.49-6.84).

CONCLUSION

Late-onset CMV infection considerably increased the risk of graft failure in patients with DGF. A hybrid preventive model including prophylaxis followed by CMV-specific cell-mediated immunity monitoring may decrease the risk of allograft failure in recipients with DGF.

Digital Slide and Simulation-Based Learning in Pre-Implantation Kidney Biopsies

Although controversial, procurement kidney biopsies and histology are commonly used in kidney allocation from deceased donors. The long series of models developed for this question, incorporating a variety of clinical and histologic variables, failed to properly predict the long-term graft survival. This failure could be explained by many factors, including the lack of expertise in terms of skilled available nephropathologists in the urgent setting of biopsies assessment. Simulation-based learning is a form of experiential learning that provides learners with a real-world-like opportunity to develop and practice their knowledge and skills but in a simulated environment. Digital pathology with whole-slide imaging is a powerful tool for knowledge delivering, as it offers the opportunity to facilitate meeting of general pathologists with experts, with availability of second opinion consultation and tailored training on specific cases. In the back of these considerations, we report on the content of the web-meeting “Digital slide and simulation-based learning in pre-implantation kidney” which was fully dedicated to the evaluation of pre-implantation kidney biopsy, with a very practical approach and a direct interaction between two expert renal transplant pathologists and the audience of general pathologists.

The strategy of diminishing age gap effect on different donor-recipient combinations in living donor kidney transplantation

BACKGROUND

The disparity between kidney donation and the number of uremic patients on the waiting list has increased the demand for older live-donor kidneys (OLK). However, the donor-recipient age gap may have an impact on the recipient's outcome.

METHODS

Patients who underwent living donor kidney transplantation at our institute between 2005 and 2019 were enrolled and categorized into four donor-recipient groups according to age (≥50 years and <50 years). The Estimated Post-Transplant Survival (EPTS) score was used to quantify the recipient's condition. Adjusted models analyzed recipient outcomes and related risks among the four groups.

RESULTS

Of the 154 pairs of live donors and recipients, OLK did not influence overall or death-censored graft survival. The four donor-recipient combinations had similar recipient outcomes, except it slightly worsened in the "old donor to young recipient" group. The EPTS score (adjusted HR, 1.02; 95% CI, 1.01-1.04; p = 0.014) and rejection (adjusted HR, 4.26; 95% CI, 1.36-13.37; p = 0.013) were significant risk factors for overall and death-censored graft survival, respectively. Recipients with pretransplant diabetes or prior solid organ transplantation could have amplified risk effects. The main causes of graft loss were death in older recipients and chronic rejection in younger recipients.

CONCLUSION

OLK is safe for young recipients. Nevertheless, adequate immunosuppression should be maintained to prevent rejection and subsequent graft loss, especially for those receiving second kidney transplantation. In contrast, older recipients should avoid overt immunosuppression and control their comorbidities, such as diabetes-related complications to improve their long-term outcomes.

Hyperspectral Imaging (HSI) of Human Kidney Allografts

OBJECTIVE

Aim of our study was to test a noninvasive HSI technique as an intraoperative real time assessment tool for deceased donor kidney quality and function in human kidney allotransplantation.

SUMMARY OF BACKGROUND DATA

HSI is capable to deliver quantitative diagnostic information about tissue pathology, morphology, and composition, based on the spectral characteristics of the investigated tissue. Because tools for objective intraoperative graft viability and performance assessment are lacking, we applied this novel technique to human kidney transplantation.

METHODS

Hyperspectral images of distinct components of kidney allografts (parenchyma, ureter) were acquired 15 and 45 minutes after reperfusion and subsequently analyzed using specialized HSI acquisition software capable to compute oxygen saturation levels (StO2), near infrared perfusion indices (NIR), organ hemoglobin indices, and tissue water indices of explored tissues.

RESULTS

Seventeen kidney transplants were analyzed. Median recipient and donor age were 55 years. Cold ischemia time was 10.8 ± 4.1 hours and anastomosis time was 35 ± 7 minutes (mean ± standard deviation). Two patients (11.8%) developed delayed graft function (DGF). cold ischemia time was significantly longer (18.6 ± 1.6) in patients with DGF (P < 0.01). Kidneys with DGF furthermore displayed significant lower StO2 (P = 0.02) and NIR perfusion indices, 15 minutes after reperfusion (P < 0.01). Transplant ureters displayed a significant decrease of NIR perfusion with increased distance to the renal pelvis, identifying well and poor perfused segments.

CONCLUSION

Intraoperative HSI is feasible and meaningful to predict DGF in renal allografts. Furthermore, it can be utilized for image guided surgery, providing information about tissue oxygenation, perfusion, hemoglobin concentration, and water concentration, hence allowing intraoperative viability assessment of the kidney parenchyma and the ureter.

Combining Clinical Parameters and Acute Tubular Injury Grading Is Superior in Predicting the Prognosis of Deceased-Donor Kidney Transplantation: A 7-Year Observational Study

Background

We developed a pragmatic dichotomous grading criterion to stratify the acute tubular injury (ATI) of deceased-donor kidneys. We intended to verify the predictive value of this criterion for the prognosis of deceased-donor kidney transplantation.

Methods

The allografts with ATI were classified into severe and mild groups. Severe ATI was defined as the presence of extreme and diffuse flattening of the tubular epithelial cells, or denudement of the tubular basement membrane. The clinical delayed graft function (DGF) risk index was calculated based on a regression model for posttransplant DGF using 17 clinical parameters related to donor–recipient characteristics.

Results

A total of 140 recipients were enrolled: 18 severe and 122 mild ATI. Compared with the mild ATI group, the severe ATI group had more donors after cardiac death, higher median donor terminal serum creatinine level (dScr), and longer median cold ischemia time. Severe ATI had a higher DGF rate (55.6% vs 14.6%, p &lt; 0.001), longer DGF recovery time (49.6 vs 26.3 days, p &lt; 0.001), and a lower estimated glomerular filtration rate (eGFR) at 1 month (23.5 vs 54.0 ml/min/1.73 m2, p &lt; 0.001), 3 months (40.4 vs 59.0, p = 0.001), and 6 months after transplant (46.8 vs 60.3, p = 0.033). However, there was no significant difference in eGFR at 1 year or beyond, graft, and patient survival. The predictive value of combined dScr with ATI severity for DGF rate and DGF recovery time was superior to that of dScr alone. The predictive value of the combined DGF risk index with ATI severity for DGF was also better than that of the DGF risk index alone; however, the association of the DGF risk index with DGF recovery time was not identified. Chronic lesions including glomerulosclerosis, interstitial fibrosis, arterial intimal fibrosis, and arteriolar hyalinosis were associated with declined posttransplant 1-year eGFR.

Conclusion

Based on our pragmatic dichotomous grading criterion for ATI in a preimplantation biopsy, donor kidneys with severe ATI increased DGF risk, prolonged DGF recovery, and decreased short-term graft function but demonstrated favorable long-term graft function. Our grading method can offer additive valuable information for assessing donor kidneys with acute kidney injury and may act as an effective supplementary index of the Banff criteria.

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

Introduction

Methods

Results

Conclusion

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.

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.

A kidney discard decision strategy based on zero-time histology analysis could lead to an unjustified increase in the organ turndown rate among ECD

The utility of zero-time kidney biopsies (KB) in deciding to accept expanded criteria donor (ECD) kidneys remains controversial. However, zero-time histology is one of the main causes for discarding kidneys in the United States. In a single-centre study, we examined the utility and impact on outcome of the use of frozen section zero-time KB among ECD. Ninety-two zero-time KB were analysed for accept/discard decision between 2005 and 2015 among ECD. 53% of kidneys were rejected after zero-time KB analysis; there was no difference in individual clinical and biological data between accepted/rejected groups. However, histology of rejected kidneys showed more sclerotic glomeruli (20% vs. 8%; P < 0.001), increased interstitial fibrosis (1.25 ± 0.12 vs. 0.47 ± 0.09; P < 0.0001), more arteriosclerosis (2.14 ± 0.17 vs. 1.71 ± 0.11; P = 0.0032) and arteriolar hyalinosis (2.15 ± 0.12 vs. 1.55 ± 0.11; P = 0.0006). Using propensity score matching, we generated a group of 42 kidney allograft recipients who received a transplant matched for donor zero-time histology and clinical characteristics with donors whose kidneys were rejected. Interestingly, their 1- and 5-year graft survival and function were similar to the global cohort of ECD recipients. In conclusion, when performed, zero-time KB was a decisive element for kidney discard decision. However, adverse zero-time histology was not associated with poorer graft survival and kidney function among ECD.

Uncovering genetic mechanisms of hypertension through multi-omic analysis of the kidney

The kidney is an organ of key relevance to blood pressure (BP) regulation, hypertension and antihypertensive treatment. However, genetically mediated renal mechanisms underlying susceptibility to hypertension remain poorly understood. We integrated genotype, gene expression, alternative splicing and DNA methylation profiles of up to 430 human kidneys to characterize the effects of BP index variants from genome-wide association studies (GWASs) on renal transcriptome and epigenome. We uncovered kidney targets for 479 (58.3%) BP-GWAS variants and paired 49 BP-GWAS kidney genes with 210 licensed drugs. Our colocalization and Mendelian randomization analyses identified 179 unique kidney genes with evidence of putatively causal effects on BP. Through Mendelian randomization, we also uncovered effects of BP on renal outcomes commonly affecting patients with hypertension. Collectively, our studies identified genetic variants, kidney genes, molecular mechanisms and biological pathways of key relevance to the genetic regulation of BP and inherited susceptibility to hypertension.

Outcome of kidney transplantation from very senior donors in Switzerland - a national cohort study

Kidney transplantation from older and marginal donors is effective to confront organ shortage. However, limitations after transplantation of kidneys from very marginal kidney donors remain unclear. We compared patient and graft outcome, achieved allograft function and quality of life of renal transplantations from Very Senior Donors (VSD, defined as donors aged 70 years and older) with Senior Donors (SD, aged 60-70 years) and Regular Donors (RD, aged younger than 60 years) in Switzerland. We evaluated the outcome of 1554 adult recipients of deceased donor kidney transplantations from 05/2008 to 12/2019; median follow-up was 4.7 years. Failure-free survival (freedom from graft loss or death), glomerular filtration rate (eGFR), and quality of life at 12 months were analyzed for RD (reference group, n = 940), SD (n = 404), and VSD (n = 210). Failure-free survival decreased with increasing donor age, mainly attributable to premature graft loss. Still, overall 5-year failure-free survival reached 83.1%, 81.0%, and 64.0% in the RD, SD, and VSD subgroups, respectively. eGFR 12 months post-transplantation was significantly higher in RD compared with SD and VSD. The acceptance rate of donor candidates for kidney TPL was 78% for the entire cohort (87% for RD, 79% for SD, and 56% for VSD). Deceased donor kidney transplantation from donors aged 70 years or older is associated with an inferior, yet acceptable failure-free outcome, with sustained quality of life.

Comprehensive assessment of deceased donor kidneys with clinical characteristics, pre-implant biopsy histopathology and hypothermic mechanical perfusion parameters is highly predictive of delayed graft function

Background: Due to the current high demand for transplant tissue, an increasing proportion of kidney donors are considered extended criteria donors, which results in a higher incidence of delayed graft function (DGF) in organ recipients. Therefore, it is important to fully investigate the risk factors of DGF, and establish a prediction system to assess donor kidney quality before transplantation.Methods: A total of 333 donation after cardiac death kidney transplant recipients were included in this retrospective study. Both univariate and multivariate analyses were used to analyze the risk factors of DGF occurrence. Receiver operating characteristic (ROC) curves were used to analyze the predictive value of variables on DGF posttransplant.Results: The donor clinical scores, kidney histopathologic Remuzzi scores and hypothermic mechanical perfusion (HMP) parameters (flow and resistance index) were all correlated. 46 recipients developed DGF postoperatively, with an incidence of 13.8% (46/333). Multivariate logistic regression analysis of the kidney transplants revealed that the independent risk factors of DGF occurrence post-transplantation included donor score (OR = 1.12, 95% CI 1.06-1.19, p < 0.001), Remuzzi score (OR = 1.21, 95% CI 1.02-1.43, p = 0.029) and acute tubular injury (ATI) score (OR = 4.72, 95% CI 2.32-9.60, p < 0.001). Prediction of DGF with ROC curve showed that the area under the curve was increased to 0.89 when all variables (donor score, Remuzzi score, ATI score and HMP resistance index) were considered together.Conclusions: Combination of donor clinical information, kidney pre-implant histopathology and HMP parameters provide a more accurate prediction of DGF occurrence post-transplantation than any of the measures alone.

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.

Organ utilization - the next hurdle in transplantation?

Nonutilization of organs from consented deceased donors remains a significant factor in limiting patient access to transplantation. Critical to reducing waste is a clear understanding of why organs are not used: accurate metrics are essential to identify the extent and causes of waste but use of these measures as targets or comparators between units/jurisdictions must be done with caution as focus on any one measure may result in unintended adverse consequences. Comparison between centres or countries may be misleading because of variation in definitions, patient or graft characteristics. Two of the most challenging areas to improve appropriate deceased donor organ utilization are appetite for risk and lack of validated tools to help identify an organ that will function appropriately. Currently, the implanting surgeon is widely considered to be accountable for the use of a donated organ so guidelines must be clear to allow and support sensible decisions and recognition that graft failure or inadvertent disease transmission are not necessarily attributable to poor decision-making. Accepting an organ involves balancing risk and benefit for the potential recipient. Novel technologies such as machine perfusion may allow for more robust guidance as to the functioning of the organ.

Utilization and Outcomes of Single and Dual Kidney Transplants from Older Deceased Donors in the United Kingdom

BACKGROUND AND OBJECTIVES

Kidneys from elderly deceased donors are often discarded after procurement if the expected outcomes from single kidney transplantation are considered unacceptable. An alternative is to consider them for dual kidney transplantation. We aimed to examine the utilization of kidneys from donors aged ≥60 years in the United Kingdom and compare clinical outcomes of dual versus single kidney transplant recipients.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Data from the United Kingdom Transplant Registry from 2005 to 2017 were analyzed. We examined utilization rates of kidneys retrieved from deceased donors aged ≥60 years, and 5-year patient and death-censored graft survival of recipients of dual and single kidney transplants. Secondary outcomes included eGFR. Multivariable analyses and propensity score analysis were used to correct for differences between the groups.

RESULTS

During the study period, 7841 kidneys were procured from deceased donors aged ≥60 years, of which 1338 (17%) were discarded; 356 dual and 5032 single kidneys were transplanted. Donors of dual transplants were older (median, 73 versus 66 years; P<0.001) and had higher United States Kidney Donor Risk Indices (2.48 versus 1.98; P<0.001). Recipients of dual transplants were also older (64 versus 61 years; P<0.001) and had less favorable human leukocyte antigen matching (P<0.001). After adjusting for confounders, dual and single transplants had similar 5-year graft survival (hazard ratio, 0.81; 95% CI, 0.59 to 1.12). No difference in patient survival was demonstrated. Similar findings were observed in a matched cohort with a propensity score analysis method. Median 12-month eGFR was significantly higher in the dual kidney transplant group (40 versus 36 ml/min per 1.73 m²; P<0.001).

CONCLUSIONS

Recipients of kidneys from donors aged ≥60 years have similar 5-year graft survival and better graft function at 12 months with dual compared with single deceased donor kidney transplants.

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.

Assessment of Organ Quality in Kidney Transplantation by Molecular Analysis and Why It May Not Have Been Achieved, Yet

Donor organ shortage, growing waiting lists and substantial organ discard rates are key problems in transplantation. The critical importance of organ quality in determining long-term function is becoming increasingly clear. However, organ quality is difficult to predict. The lack of good measures of organ quality is a serious challenge in terms of acceptance and allocation of an organ. The underlying review summarizes currently available methods used to assess donor organ quality such as histopathology, clinical scores and machine perfusion characteristics with special focus on molecular analyses of kidney quality. The majority of studies testing molecular markers of organ quality focused on identifying organs at risk for delayed graft function, yet without prediction of long-term graft outcome. Recently, interest has emerged in looking for molecular markers associated with biological age to predict organ quality. However, molecular gene sets have not entered the clinical routine or impacted discard rates so far. The current review critically discusses the potential reasons why clinically applicable molecular quality assessment using early kidney biopsies might not have been achieved yet. Besides a critical analysis of the inherent limitations of surrogate markers used for organ quality, i.e., delayed graft function, the intrinsic methodological limitations of studies assessing organ quality will be discussed. These comprise the multitude of unpredictable hits as well as lack of markers of nephron mass, functional reserve and regenerative capacity.

Kidney Perfusion as an Organ Quality Assessment Tool-Are We Counting Our Chickens Before They Have Hatched?

The final decision to accept an organ for transplantation remains a subjective one. With “poor organ quality” commonly cited as a major reason for kidney discard, accurate, objective, and reliable quality assessment is essential. In an era of increasingly higher-risk deceased donor kidneys, the catch is to accept those where the risk–benefit scale will tip in the right direction. Currently available assessment tools, such as risk-scores predicting outcome and zero-time biopsy, perform unsatisfactory, and assessment options during static cold storage are limited. Kidney perfusion technologies are finding their way into clinical practice, and they bring a new opportunity to assess kidney graft viability and quality, both in hypothermic and normothermic conditions. We give an overview of the current understanding of kidney viability assessment during ex situ kidney perfusion. A pragmatic framework to approach viability assessment is proposed as an interplay of three different compartments: the nephron, the vascular compartment, and the immune compartment. Although many interesting ways to assess kidney injury and function during perfusion have been proposed, none have reached the stage where they can reliably predict posttransplant outcome. Larger well-designed studies and validation cohorts are needed to provide better guidance.

Perirenal Adipose Tissue Displays an Age-Dependent Inflammatory Signature Associated With Early Graft Dysfunction of Marginal Kidney Transplants

Background: Better understanding of the contribution of donor aging and comorbidity factors of expanded criteria donors (ECD) to the clinical outcome of a transplant is a challenge in kidney transplantation. We investigated whether the features of donor-derived stromal vascular fraction of perirenal adipose tissue (PRAT-SVF) could be indicative of the deleterious impact of the ECD microenvironment on a renal transplant.

Methods: A comparative analysis of cellular components, transcriptomic and vasculogenic profiles was performed in PRAT-SVF obtained from 22 optimal donors and 31 ECD deceased donors. We then investigated whether these parameters could be associated with donor aging and early allograft dysfunction.

Results: When compared with the PRAT-SVF of non-ECD donors, ECD PRAT-SVF displayed a lower proportion of stromal cells, a higher proportion of inflammatory NK cells. The global RNA sequencing approach indicated a differential molecular signature in the PRAT-SVF of ECD donors characterized by the over-expression of CXCL1 and IL1-β inflammatory transcripts. The vasculogenic activity of PRAT-SVF was highly variable but was not significantly affected in marginal donors. Periorgan recruitment of monocytes/macrophages and NK cells in PRAT-SVF was associated with donor aging. The presence of NK cell infiltrates was associated with lower PRAT-SVF angiogenic activity and with early allograft dysfunction evaluated on day 7 and at 1 month post-transplant.

Conclusions: Our results indicate that human NK cell subsets are differentially recruited in the periorgan environment of aging kidney transplants. We provide novel evidence that PRAT-SVF represents a non-invasive and timely source of donor material with potential value to assess inflammatory features that impact organ quality and function.

Pre-implantation kidney biopsy: value of the expertise in determining histological score and comparison with the whole organ on a series of discarded kidneys

BACKGROUND

Evidence about the reliability of pre-implantation biopsy is still conflicting, depending on both biopsy type and pathologist's expertise. Aim of the study is to evaluate the agreement of general v specialist pathologists and to compare scores on biopsy and whole organs in a set of discarded kidneys.

METHODS

46 discarded kidneys were identified with their corresponding biopsies. The biopsies were reviewed by three general and two specialist pathologists, blinded to the original report, according to Remuzzi score. The intraclass correlation coefficient (ICC) was calculated for both groups. Discarded kidneys were scored according to Remuzzi score by a single specialist pathologist. Biopsies and organs were compared by Wilcoxon signed rank test. Weighted κ coefficients between biopsy and organ scores were also calculated.

RESULTS

Specialist pathologists achieved higher values of ICC, reaching excellent or good agreement in most of the parameters, while general pathologists values were mainly fair or good. On whole organs, scores were consistently lower than biopsies, with a significant difference in most of the parameters. Weighted κ coefficient was slight or fair for most of the parameters.

CONCLUSIONS

Our data suggests that the creation of a pool of specialist pathologists would improve organ utilization. Moreover, biopsies are not representative of the whole organ. As the Remuzzi score on biopsy is a major reasons for discard, a quota of transplantable kidneys may be erroneously discarded. Refinement in Remuzzi cut-offs based on expert reporting and recognition of sampling error of biopsies in correlation with clinical outcome data should be undertaken.

Histological and clinical evaluation of marginal donor kidneys before transplantation: Which is best?

Organ shortage represents one of the major limitations to the development of kidney transplantation. To increase the donor pool and to answer the ever increasing kidney request, physicians are recurring to marginal kidneys as kidneys from older donors, from hypertensive or diabetic donors and from non-heart beating donors. These kidneys are known to have frequently a worse outcome in the recipients. To date major problem is to evaluate such kidneys in order to use or to discard them before transplantation. The use of such kidneys create other relevant question as whether to use them as single or dual transplant and to allocate them fairly according transplant programs. The pre-transplant histological evaluation, the clinical evaluation of the donor or both the criteria joined has been used and according the time each criterion prevailed over the others. Aim of this review has been to examine the advantages and the drawbacks of any criterion and how they have changed with time. To date any criterion has several limitations and several authors have argued for the development of new guidelines in the field of the kidney evaluation for transplantation. Several authors argue that the use of omic technologies should improve the organ evaluation and studies are ongoing to evaluate these technologies either in the donor urine or in the biopsies taken before transplantation.

Pretransplant Biopsy of Marginal Kidneys: Is It Necessary?

INTRODUCTION

Pretransplant kidney biopsy from marginal donors is used to guide the decision of whether to accept or discard organs for transplantation; however, there is controversy about this procedure, and the need for a pretransplant biopsy is still a debate. We sought to determine if histologic evaluation before implantation of marginal kidneys would influence the outcome.

METHODS

A retrospective observational cohort study of marginal donor transplants at Centro Hospitalar e Universitário de Coimbra was done. From 2009 to 2016, 650 marginal kidney transplants were analyzed. We evaluated long-term graft survival in a cohort of patients who received marginal kidneys. The recipients were divided into 2 groups based on whether a pretransplant donor biopsy was performed. Continuous variables were summarized by mean and standard deviation or median and range, as applicable. Categorical variables were summarized by relative and absolute frequencies. The survival analysis was obtained and plotted using the Kaplan-Meier method and compared with the log-rank test.

RESULTS

The median age of recipients and donors were statistically different between both groups (P < .001), with the donors and the recipients being younger in the group without a pretransplant biopsy. The median cold ischemia time was higher in the biopsy group (P = .01). The survival analysis showed that graft survival didn't differ between the groups (P = .2).

CONCLUSIONS

Selection of kidneys based on histological findings may not influence the graft survival and implies a higher cold ischemia time. More data are necessary to provide insight into which clinical, histologic, and biochemical parameters are necessary for decision making on kidney acceptance.

Oxalate deposition in renal allograft biopsies within 3 months after transplantation is associated with allograft dysfunction

BACKGROUND

Calcium oxalate (CaOx) deposition in the kidney may lead to loss of native renal function but little is known about the prevalence and role of CaOx deposition in transplanted kidneys.

METHODS

In patients transplanted in 2014 and 2015, all for-cause renal allograft biopsies obtained within 3 months post-transplantation were retrospectively investigated for CaOx deposition. Additionally, all preimplantation renal biopsies obtained in 2000 and 2001 were studied.

RESULTS

In 2014 and 2015, 388 patients were transplanted, of whom 149 had at least one for-cause renal biopsy. Twenty-six (17%) patients had CaOx deposition. In the population with CaOx deposition: Patients had significantly more often been treated with dialysis before transplantation (89 vs. 64%; p = 0.011); delayed graft function occurred more frequently (42 vs. 23%; p = 0.038); and the eGFR at the time of first biopsy was significantly worse (21 vs. 29 ml/min/1.73m2; p = 0.037). In a multivariate logistic regression analysis, eGFR at the time of first biopsy (OR 0.958, 95%-Cl: 0.924-0.993, p = 0.019), dialysis before transplantation (OR 4.868, 95%-Cl: 1.128-21.003, p = 0.034) and the time of first biopsy after transplantation (OR 1.037, 95%-Cl: 1.013-1.062, p = 0.002) were independently associated with CaOx deposition. Graft survival censored for death was significantly worse in patients with CaOx deposition (p = 0.018). In only 1 of 106 preimplantation biopsies CaOx deposition was found (0.94%).

CONCLUSION

CaOx deposition appears to be primarily recipient-derived and is frequently observed in for-cause renal allograft biopsies obtained within 3 months post-transplantation. It is associated with inferior renal function at the time of biopsy and worse graft survival.

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.

Molecular insights into genome-wide association studies of chronic kidney disease-defining traits

Genome-wide association studies (GWAS) have identified >100 loci of chronic kidney disease-defining traits (CKD-dt). Molecular mechanisms underlying these associations remain elusive. Using 280 kidney transcriptomes and 9958 gene expression profiles from 44 non-renal tissues we uncover gene expression partners (eGenes) for 88.9% of CKD-dt GWAS loci. Through epigenomic chromatin segmentation analysis and variant effect prediction we annotate functional consequences to 74% of these loci. Our colocalisation analysis and Mendelian randomisation in >130,000 subjects demonstrate causal effects of three eGenes (NAT8B, CASP9 and MUC1) on estimated glomerular filtration rate. We identify a common alternative splice variant in MUC1 (a gene responsible for rare Mendelian form of kidney disease) and observe increased renal expression of a specific MUC1 mRNA isoform as a plausible molecular mechanism of the GWAS association signal. These data highlight the variants and genes underpinning the associations uncovered in GWAS of CKD-dt.

Donor-related diabetic nephropathy: a comprehensive clinicopathological study

Knowledge on renal involvement in kidney donors with diabetes, that is, diabetic nephropathy (DN), is limited. During the 7 years (2010-2017), 921 postperfusion biopsies were performed for living donors (14%) or deceased donors (86%). The Renal Pathology Society classification schema for DN (class 0-IV) was used. Biopsies with light microscopic changes of DN (at least class IIa) were selected for study. Eleven biopsies (1.2%) showed DN, all from deceased donors (class IIa in 8, class IIb in 2, and class III in 1 biopsy). The glomerular basement membrane thickness ranged from 439 ± 52 to 725 ± 82 nm. These biopsies also displayed arterionephrosclerosis. They were from 9 deceased donors (fulfilling clinical criteria for acceptance in all, diabetes ;[>6 years] in 8, hypertension in 6, and proteinuria [1+] in all). Follow-up biopsies (5-342 weeks after transplant) showed DN of the same class (7 biopsies), probably progression (1), or progression (3). At follow-up (15-416 weeks), all recipients were alive. One graft was lost at 76 weeks because of progressive DN. The other 10 grafts were functioning, but the serum creatinine reached 2.0 to 2.7 mg/dL in 5 of them. Although diabetes is frequent in kidney donors, donor-related DN is unusual. It is observed only in deceased donors, but the risk factors for its development are not known. Donor-related DN may be stable or progress. Whether it resolves, especially for DN in early phase, remains unknown. It may adversely impact the graft outcome with a magnitude proportional to the severity of the tissue injury in the postperfusion biopsies.

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

BACKGROUND

Efforts to maximize transplantation by matching organ quality to recipient longevity require reliable tools. The US kidney allocation system uses the Kidney Donor Risk Index (KDRI) for this purpose, and many centers additionally rely on donor biopsies. The Leuven score combines donor age with procurement histology (glomerulosclerosis and interstitial fibrosis/tubular atrophy) to predict allograft survival.

METHODS

We compared KDRI with Leuven scores for associations with kidney discard, delayed graft function, and allograft function and survival. We used Cox, modified Poisson, and linear regression to calculate risks based on KDRI and (separately) Leuven scores, adjusting for important transplant and recipient variables.

RESULTS

From 890 donors, 1729 kidneys were procured and biopsied. Five hundred eighty-five (34%) kidneys were discarded. Median donor age was 53 years (interquartile range [IQR], 44-61 years). Median KDRI and Leuven scores were 1.56 (IQR, 1.28-1.90) and 59 (IQR, 49-69). Relative risk for discard was 1.21 (95% confidence interval [CI], 1.17-1.24) per 0.2-unit increase in KDRI and 1.38 (1.31-1.46) per 10-unit increase in Leuven score. Adjusted relative risks for delayed graft function were 0.98 (95% CI, 0.94-1.02) and 0.94 (95% CI, 0.90-0.99), adjusted hazard ratios for graft failure were 1.10 (95% CI, 1.04-1.16) and 1.11 (95% CI, 1.02-1.21), and adjusted linear regression coefficients for 3-year estimated glomerular filtration rate were -3.88 (-4.63 to -3.13) and -5.18 (-6.19 to -4.18).

CONCLUSIONS

In kidneys clinically selected for procurement biopsy, the Leuven score was more strongly associated with discard but performed similarly to KDRI for predicting transplant outcomes, suggesting the need to reevaluate current procurement biopsy practices. Given modest associations for both tools; however, neither KDRI nor the Leuven score should be used in isolation for individual organ acceptance decisions.

European Association of Urology Guidelines on Renal Transplantation: Update 2018

CONTEXT

The European Association of Urology (EAU) panel on renal transplantation (RT) has released an updated version of the RT guidelines.

OBJECTIVE

To present the 2018 EAU guidelines on RT.

EVIDENCE ACQUISITION

A broad and comprehensive scoping exercise was performed, encompassing all areas of RT guidelines published between January 1, 2007, and May 31, 2016. Databases covered by the search included Medline, Embase, and the Cochrane Libraries. Previous guidelines were updated, and levels of evidence and grades of recommendation were assigned.

EVIDENCE SYNTHESIS

It is strongly recommended to offer pure or hand-assisted laparoscopic/retroperitoneoscopic surgery as the preferential technique for living donor nephrectomy. Decisions on the acceptance of a donor organ should not be based on histological findings alone since this might lead to an unnecessarily high rate of discarded grafts. For ureterovesical anastomosis, a Lich-Gregoir-like extravesical technique protected by a ureteral stent is the preferred technique for minimisation of urinary tract complications. It is also strongly recommended to perform initial rejection prophylaxis with a combination therapy comprising a calcineurin inhibitor (preferably tacrolimus), mycophenolate, steroids, and an induction agent (either basiliximab or anti-thymocyte globulin). The long version of the guidelines is available at the EAU website (http://uroweb.org/guidelines).

CONCLUSIONS

These abridged EAU guidelines present updated information on the clinical and surgical management of RT for incorporation into clinical practice.

PATIENT SUMMARY

The European Association of Urology has released the renal transplantation guidelines. The implementation of minimally invasive surgery for organ retrieval and the latest evidence on transplant surgery as well as on immunosuppressive regimens are key factors for minimisation of rejection and achievement of long-term graft survival.

Systematic review of kidney transplantation functional predictors

CONTEXT

Kidney transplantation from donors with expanded criteria has increased the pool of kidneys at the cost of a higher risk of short and long-term graft dysfunction. The main issue lies in determining which kidneys will offer acceptable function and survival compared with the risk represented by surgery and subsequent immunosuppression.

OBJECTIVE

The objective of our article is to review the current evidence on the tools for predicting the functionality of kidney transplantation from cadaveric donors with expanded criteria and determining the validity for their use in standard practice.

ACQUISITION OF EVIDENCE

We conducted a systematic literature review according to the PRISM criteria, through Medline (http://www.ncbi.nlm.nih.gov) and using the keywords (in isolation or in conjunction) "cadaveric renal transplantation; kidney graft function appraisal, graft function predictors". We selected prospective and retrospective series and review articles. A total of 375 articles were analysed, 39 of which were ultimately selected for review.

SUMMARY OF THE EVIDENCE

The predictors of functionality include the following: The donor risk indices; the calculation of the renal functional weight or the assessment of the nephronic mass; the measurement of vascular resistances during perfusion in hypothermia; the measurement of the donor's biomarkers in urine and in the perfusion liquid; the measurement of functional and reperfusion parameters in normothermia; and the measurement of morphological parameters (microscopic and macroscopic) of the target organ. In this article, we present an explanatory summary of each of these parameters, as well as their most recent evidence on this issue.

DISCUSSION

None of the reviewed parameters in isolation could reliably predict renal function and graft survival. There is a significant void in terms of the macroscopic assessment of kidney transplantation.

CONCLUSIONS

We need to continue developing predictors of renal functionality to accurately define the distribution of each currently available donor kidney.

Preimplantation Kidney Biopsies of Extended Criteria Donors Have a Heavier Inflammatory Burden Than Kidneys From Standard Criteria Donors

Background

Donors after brain death develop a systemic proinflammatory state that may predispose the kidneys to injury after transplantation. Because it is not known whether this inflammatory environment similarly affects the kidneys from expanded criteria donor (ECD) and standard criteria donors (SCD), we sought to evaluate differences in the gene expression of inflammatory cytokines in preimplantation biopsies (PIBx) from ECD and SCD kidneys.

Methods

Cytokines gene expression was measured in 80 PIBx (SCD, 52; ECD, 28) and associated with donor variables.

Results

Normal histology and chronic histological lesions were not different between both types of kidneys. ECD kidneys showed significant increase in the transcripts of MCP-1, RANTES, TGF-β1, and IL-10 when compared with SCD. Kidneys presenting normal histology had similar inflammatory profile except by a higher expression of RANTES observed in ECD (P = 0.04). Interstitial fibrosis and tubular atrophy (interstitial fibrosis and tubular atrophy ≥ 1) were associated with higher expression of TGF-β1, RANTES, and IL-10 in ECD compared with SCD kidneys. Cold ischemia time of 24 hours or longer was significantly associated with upregulation of FOXP3, MCP-1, RANTES, and IL10, whereas longer duration of donor hospitalization significantly increased gene expression of all markers. High FOXP3 expression was also associated with lower level of serum creatinine at 1 year. Donor age was not associated with any of the transcripts studied.

Conclusions

PIBx of ECD exhibit a higher gene expression of inflammatory cytokines when compared with SCD kidneys. This molecular profile may be a specific ECD kidney response to brain death and may help to predict the posttransplant outcomes of ECD recipients.

Establishing Biomarkers in Transplant Medicine: A Critical Review of Current Approaches

Although the management of kidney transplant recipients has greatly improved over recent decades, the assessment of individual risks remains highly imperfect. Individualized strategies are necessary to recognize and prevent immune complications early and to fine-tune immunosuppression, with the overall goal to improve patient and graft outcomes. This review discusses current biomarkers and their limitations, and recent advancements in the field of noninvasive biomarker discovery. A wealth of noninvasive monitoring tools has been suggested that use easily accessible biological fluids such as urine and blood, allowing frequent and sequential assessments of recipient's immune status. This includes functional cell-based assays and the evaluation of molecular expression on a wide spectrum of platforms. Nevertheless, the translation and validation of exploratory findings and their implementation into standard clinical practice remain challenging. This requires dedicated prospective interventional trials demonstrating that the use of these biomarkers avoids invasive procedures and improves patient or transplant outcomes.