Fibrous Intimal Thickening at Implantation Adversely Affects Long-Term Kidney Allograft Function

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.

Human kidney graft survival correlates with structural parameters in baseline biopsies: a quantitative observational cohort study with more than 14 years' follow-up

This prospective cohort study evaluates associations between structural and ultrastructural parameters in baseline biopsies from human kidney transplants and long-term graft survival after more than 14 years' follow-up. Baseline kidney graft biopsies were obtained prospectively from 54 consecutive patients receiving a kidney transplant at a single institution. Quantitative measurements were performed on the baseline biopsies by computer-assisted light microscopy and electron microscopy. Stereology-based techniques estimated the fraction of interstitial tissue, the volume of glomeruli, mesangial fraction, and basement membrane thickness of glomerular capillaries. The fraction of occluded glomeruli and scores according to the Banff classification were achieved. Kidney graft survival was analyzed by Kaplan-Meier estimates and Cox regression. Association to long-term kidney function was also analyzed. The long-term surviving kidney transplants were characterized at implantation by less arteriolar hyaline thickening (P < 0.001) and less interstitial fibrosis (P = 0.001), as well as a lower fraction of occluded glomeruli (P = 0.004) and lower glomerular volume (P = 0.03). At the latest follow-up, eGFR was decreased by 12 ml/min/1.73 m² per unit increase in the score for arteriolar hyalinosis at implantation (P = 0.02), and eGFR was decreased by 19 ml/min/1.73 m² per 10⁶ μm³ increase in glomerular volume at baseline (P = 0.03). The unbiased Cavalieri estimate of glomerular volume and the ultrastructural parameters are the first to be evaluated in a cohort study with prospective follow-up for more than 14 years. The study shows that baseline biopsies from human kidney grafts contain extraordinary long-term prognostic information, and it highlights the importance of these intrinsic graft factors.

Does Histopathology of Implanted Kidney According to Banff 07 Help Predict Long-term Transplantation Outcome?

Analyses of peritransplant biopsies of deceased-donor kidneys show high incidence of chronic abnormalities. The question arises whether chronic abnormalities present at implantation determine engrafted kidney fate regardless of other concomitant variables. The aim of this study was to identify risk factors of graft loss considering histopathological changes present at implantation scored according to Banff 07 criteria.

PATIENTS AND METHODS

Inclusion criteria (n = 300) was engraftment between years 2000 and 2008 and availability of implantation biopsy. Analyzed abnormalities present in donor biopsy were arteriolar hyalinization, interstitial fibrosis, intimal sclerotization, tubular atrophy, total inflammation, and percentage of sclerotic glomeruli (Banff classification). Allograft function was estimated by abbreviated Modification of Diet in Renal Disease formula and proteinuria semi-quantitatively by standard dip-stick test. Kaplan-Meier estimate was used to assess graft survival. Searching for independent risk factors of graft survival was performed by means of Cox proportional hazards models (SAS System, SAS Institute Inc, Cary, NC, United States).

RESULTS

In one-factor analyses, predictors of kidney allograft loss were donor age, donor history of diabetes, kidney allograft dysfunction within first posttransplant year, and recipient chronic hepatitis C. In terms of chronic abnormalities, arteriolar hyalinization of any intensity nearly doubled the risk of allograft loss. Independent risk factors of kidney allograft loss in multivariate analysis were donor age, posttransplant diabetes mellitus, proteinuria after engraftment, and recipient hepatitis C.

CONCLUSION

The effect of arteriolar hyalinization on renal transplant survival is probably interwoven with other predictors of graft loss. Recognizing the negative impact of recipient chronic hepatitis C on graft survival, hepatitis C virus treatment should be provided to patients with advanced chronic kidney disease, patients on wait lists, or patients already transplanted.

Zero-Time Renal Transplant Biopsies: A Comprehensive Review

Zero-time kidney biopsies, obtained at time of transplantation, are performed in many transplant centers worldwide. Decisions on kidney discard, kidney allocation, and choice of peritransplant and posttransplant treatment are sometimes based on the histological information obtained from these biopsies. This comprehensive review evaluates the practical considerations of performing zero-time biopsies, the predictive performance of zero-time histology and composite histological scores, and the clinical utility of these biopsies. The predictive performance of individual histological lesions and of composite scores for posttransplant outcome is at best moderate. No single histological lesion or composite score is sufficiently robust to be included in algorithms for kidney discard. Dual kidney transplantation has been based on histological assessment of zero-time biopsies and improves outcome in individual patients, but the waitlist effects of this strategy remain obscure. Zero-time biopsies are valuable for clinical and translational research purposes, providing insight in risk factors for posttransplant events, and as baseline for comparison with posttransplant histology. The molecular phenotype of zero-time biopsies yields novel therapeutic targets for improvement of donor selection, peritransplant management and kidney preservation. It remains however highly unclear whether the molecular expression variation in zero-time biopsies could become a better predictor for posttransplant outcome than donor/recipient baseline demographic factors.

Recipient Outcomes Following Transplantation of Allografts From Live Kidney Donors Who Subsequently Developed End-Stage Renal Disease

Live kidney donors have an increased risk of end-stage renal disease (ESRD) compared with nondonors; however, it is unknown whether undetected, subclinical kidney disease exists at donation that subsequently contributes to this risk. To indirectly test this hypothesis, the authors followed the donated kidneys, by comparing the outcomes of 257 recipients whose donors subsequently developed ESRD with a matched cohort whose donors remained ESRD free. The compared recipients were matched on donor (age, sex, race/ethnicity, donor-recipient relationship), transplant (HLA mismatch, peak panel-reactive antibody, previous transplantation, year of transplantation), and recipient (age, sex, race/ethnicity, body mass index, cause of ESRD, and time on dialysis) risk factors. Median recipient follow-up was 12.5 years (interquartile range 7.4-17.9, maximum 20 years). Recipients of allografts from donors who developed ESRD had increased death-censored graft loss (74% versus 56% at 20 years; adjusted hazard ratio [aHR] 1.7; 95% confidence interval [CI] 1.5-2.0; p < 0.001) and mortality (61% versus 46% at 20 years; aHR 1.5; 95% CI 1.2-1.8; p < 0.001) compared with matched recipients of allografts from donors who did not develop ESRD. This association was similar among related, spousal, and unrelated nonspousal donors. These findings support a novel view of the mechanisms underlying donor ESRD: that of pre-donation kidney disease. However, biopsy data may be required to confirm this hypothesis.

German recommendations for pretransplantation donor kidney biopsies

PURPOSE

This manuscript reviews the data about the histopathologic and develops recommendations to standardise and improve the biopsy procedure, the biopsy handling, the histopathological evaluation, the communication of results and the collection of data from pretransplantation kidney biopsies of deceased donors in Germany.

METHODS

The recommendations are based on this literature review, on discussions at two workshops held by the German Society of Pathology and the German Organ Transplantation Foundation and on personal experiences of the authors.

RESULTS

These German recommendations advocate the use of punch biopsies, paraffin embedding and detailed descriptive reporting of histopathological findings.

CONCLUSIONS

These recommendations constitute only a starting point. Periodical revisions will help to simplify and optimise the recommendations with the ultimate goal to prospectively gather data for the elaboration of a computer-based algorithm that allows the exact prediction of transplantation outcome for a given match of donor and recipient.

Expanding the pool of kidney donors: use of kidneys with acute renal dysfunction

Given the shortage of organs transplantation, some strategies have been adopted by the transplant community to increase the supply of organs. One strategy is the use of expanded criteria for donors, that is, donors aged >60 years or 50 and 59 years, and meeting two or more of the following criteria: history of hypertension, terminal serum creatinine >1.5mg/dL, and stroke as the donor´s cause of death. In this review, emphasis was placed on the use of donors with acute renal failure, a condition considered by many as a contraindication for organ acceptance and therefore one of the main causes for kidney discard. Since these are well-selected donors and with no chronic diseases, such as hypertension, renal disease, or diabetes, many studies showed that the use of donors with acute renal failure should be encouraged, because, in general, acute renal dysfunction is reversible. Although most studies demonstrated these grafts have more delayed function, the results of graft and patient survival after transplant are very similar to those with the use of standard donors. Clinical and morphological findings of donors, the use of machine perfusion, and analysis of its parameters, especially intrarenal resistance, are important tools to support decision-making when considering the supply of organs with renal dysfunction.

Contrast-enhanced ultrasonography in the early period after kidney transplantation predicts long-term allograft function

INTRODUCTION

Real-time contrast-enhanced sonography (CES) can assess microvascular tissue perfusion using gas-filled microbubbles. The purpose of the study was to evaluate the feasibility of early CES in predicting long-term kidney allograft function in comparison to color Doppler ultrasonography (CDUS).

METHODS

We prospectively studied 68 consecutive kidney transplant recipients using CES and conventional CDUS investigation 1 week after transplantation. Transplant tissue perfusion imaging was performed by low-power imaging during intravenous administration of the sonocontrast SonoVue. Renal tissue perfusion was assessed quantitatively using flash replenishment kinetics of microbubbles to estimate renal blood flow (RBF). The obtained sonography values were correlated with clinical data 1 week up to 1 year after transplantation.

RESULTS

In contrast with conventional CDUS resistive indices, RBF estimated by CES 1 week posttransplantation significantly correlated with kidney function after 1 year (r = 0.67; P < .001). Determination of RBF by CES revealed a significant correlation with donor age but not recipient age, whereas conventional CDUS resistive index was significantly correlated to recipient age (r = 0.54; P < .001) but not donor age. Furthermore RBF was associated with vascular fibrosis and intimal thickening of the engraftment biopsies.

CONCLUSION

This is the first prospective study demonstrating the prognostic value of CES early after kidney transplantation. In contrast with CDUS, CES reveals information about kidney allograft perfusion independent of recipient vascular compliance.

Short-term prognosis of living-donor kidney transplantation from hypertensive donors with high-normal albuminuria

BACKGROUND

High-normal albuminuria (HNA) is an independent predictor of cardiovascular risk in the general population. Although hypertensive donor (HTD) candidates with HNA were considered acceptable donors by the Amsterdam Forum 2004, the transplant prognosis of HTDs with HNA has not been determined. Therefore, we investigated the transplant prognosis of HTDs with HNA.

METHODS

We retrospectively analyzed 52 adult living-donor kidney transplants performed at Kagawa University Hospital. HNA was defined as albuminuria of 15 to 30 mg/g Cr. Changes in kidney function of donors and recipients were assessed up to 2 years after transplantation.

RESULTS

Overall, 38 donors were normotensive and 14 were hypertensive. Nine of 14 HTDs exhibited HNA before donation. More HTDs with HNA had arteriosclerotic vasculopathy or glomerulosclerosis than did normotensive donors (NTDs). Hypertension and the degree of albuminuria did not affect the donors' posttransplantation kidney function. The risk of discompensatory changes in kidney function after donation was significantly higher in HTDs with HNA than in NTDs (odds ratio, 10.5; 95% confidence interval, 1.51-72.9; P=0.02). In multivariate analysis, the coexistence of hypertension and HNA was not significantly associated with discompensatory changes after donation (adjusted odds ratio, 6.04; 95% confidence interval, 0.19-192; P=0.31). Recipients of HTDs with HNA had similar allograft survival rates but lower allograft function compared with recipients of NTDs.

CONCLUSIONS

Although further studies are needed to confirm our results, the short-term prognosis of living-donor kidney transplantation was similar between HTDs with HNA and NTDs.

Kidneys at higher risk of discard: expanding the role of dual kidney transplantation

Half of the recovered expanded criteria donor (ECD) kidneys are discarded in the United States. A new kidney allocation system offers kidneys at higher risk of discard, Kidney Donor Profile Index (KDPI)>85%, to a wider geographic area to promote broader sharing and expedite utilization. Dual kidney transplantation (DKT) based on the KDPI is a potential option to streamline allocation of kidneys which otherwise would have been discarded. To assess the clinical utility of the KDPI in kidneys at higher risk of discard, we analyzed the OPTN/UNOS Registry that included the deceased donor kidneys recovered between 2002 and 2012. The primary outcomes were allograft survival, patient survival and discard rate based on different KDPI categories (<80%, 80-90% and >90%). Kidneys with KDPI>90% were associated with increased odds of discard (OR=1.99, 95% CI 1.74-2.29) compared to ones with KDPI<80%. DKTs of KDPI>90% were associated with lower overall allograft failure (HR=0.74, 95% CI 0.62-0.89) and better patient survival (HR=0.79, 95% CI 0.64-0.98) compared to single ECD kidneys with KDPI>90%. Kidneys at higher risk of discard may be offered in the up-front allocation system as a DKT. Further modeling and simulation studies are required to determine a reasonable KDPI cutoff percentile.

The predictive value of kidney allograft baseline biopsies for long-term graft survival

The effect of baseline histology and individual histologic lesions at the time of transplantation on long-term graft survival has been evaluated using different scoring systems, but the predictive capacity of these systems has not been adequately validated. All kidney recipients transplanted in a single institution between 1991 and 2009 who underwent a baseline kidney allograft biopsy at transplantation were included in this prospective study (N=548). All baseline biopsies were rescored according to the updated Banff classification, and the relationship between the individual histologic lesions and donor demographics was assessed using hierarchical clustering and principal component analysis. Survival analysis was performed using Cox proportional hazards analysis and log-rank testing. Mean follow-up time was 6.7 years after transplantation. Interstitial fibrosis, tubular atrophy, and glomerulosclerosis associated significantly with death-censored graft survival, whereas arteriolar hyalinosis and vascular intimal thickening did not. Notably, donor age correlated significantly with interstitial fibrosis, tubular atrophy, and glomerulosclerosis and associated independently with graft survival. On the basis of these findings, a novel scoring system for prediction of 5-year graft survival was constructed by logistic regression analysis. Although the predictive performance of previously published histologic scoring systems was insufficient to guide kidney allocation in our cohort (receiver operating characteristic area under the curve ≤0.62 for each system), the new system based on histologic data and donor age was satisfactory for prediction of allograft loss (receiver operating characteristic area under the curve = 0.81) and may be valuable in the assessment of kidney quality before transplantation.

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.

Intimal hyperplasia: slow but deadly

Intimal hyperplasia is the leading cause of long-term failure in coronary artery bypass vein grafting, coronary artery stenting, angioplasty, arteriovenous fistula for dialysis, and allograft transplantation. Intimal hyperplasia is a product of vascular smooth muscle cell proliferation, migration through the internal elastic lamina, and deposition of extracellular matrix proteins driven by growth factors in the vasculature. This vascular pathology results in a progressive diminution of the vessel lumen and serves as a site for thrombosis and atherosclerotic lesions. A key cell type in the initiation of intimal hyperplasia is the vascular endothelial cell, which appears to have down-stream effects on the vascular smooth muscle proliferation and migration. Currently, the only means available for prevention of intimal hyperplasia is through inhibition of mammalian target of rapamycin (mTOR) with the immunosuppressant rapamycin. mTOR integrates up-stream signals from growth factors such as IL-2 and senses the cellular nutrient and energy levels and redox status. This presentation will discuss the potential means of preserving the vascular endothelial cell and, thereby, reducing the development of intimal hyperplasia in our open-heart surgical patients.

With respect to elderly patients: finding kidneys in the context of new allocation concepts

The elderly have benefited from increased access to renal transplantation in recent years. New allocation concepts would shift distribution of kidneys to younger recipients, making expanded criteria and living donor kidneys more relevant for seniors. Current issues impacting expanded criteria donor kidney availability and living donor transplant opportunities for the elderly are explored. It is hoped that the kidney donor profile index will improve risk assessment and utilization of marginal kidneys. The usefulness of procurement biopsy remains controversial. Dual kidney transplantation and machine perfusion appear to be effective mechanisms to increase organ availability. "Old-for-old" allocation systems, donation service area variation and regulatory and reimbursement issues highlight disparities and disincentives affecting expanded criteria donor organ utilization, and considerations for the way forward are discussed. Living donor transplantation, even with older donors, may provide the best option for elderly recipients, and careful expansion of the living donor pool appears appropriate. In light of new allocation concepts, it will be important to understand issues pertinent to seniors and develop effective strategies to maintain or improve their access to the benefits of transplantation.

Peritransplant kidney biopsies: comparison of pathologic interpretations and practice patterns of organ procurement organizations

The preimplantation kidney biopsy affects utilization by diagnosing glomerulosclerosis, interstitial fibrosis (IF), arteriosclerosis, and arteriolar hyalinosis. Organ procurement organizations (OPOs) determine whether a donor warrants this biopsy and the donor hospital pathologists (DHPs) report on an OPO-specific pathology interpretation form. Biopsy slides from 40 deceased donor kidneys transplanted at our institution were used to compare interpretations between our transplant pathologist and the DHPs. Thirty-three of these kidneys also had post-perfusion biopsies (PPB). All 58 OPOs were queried for criteria used to request a preimplantation biopsy, and their pathology interpretation forms were also analyzed. The transplant and DHPs had substantial agreement for percent glomerulosclerosis with 75% of biopsies being interpreted within five percentage points. Concordance for IF was poor. The DHP rarely reported arterial pathology. Seventy percent of preimplantation and PPB were read similarly for glomerulosclerosis; concordance for other lesions was weaker. There were no cues for arterial disease on our OPO's pathology interpretation form. Criteria for obtaining a preimplantation biopsy lacked uniformity for the 21 OPOs with a self-generated policy. The pathology interpretation forms varied widely among the OPOs. Current OPO practices with regard to the preimplantation biopsy should be improved.

Pre-existing arteriosclerotic intimal thickening in living-donor kidneys reflects allograft function

BACKGROUND

Donor shortage is a serious problem worldwide and it is now debated whether kidneys from marginal donors are suitable for renal transplantation. Recent studies have shown that the findings of preimplantation kidney biopsy are useful to evaluate vasculopathy in the donated kidney, and may predict transplant outcomes in deceased- donor kidney transplantation. However, few studies have focused on the pathological findings of preimplantation biopsy in living-donor kidney transplantation. Therefore, we investigated whether arteriosclerotic vasculopathy in living-donor kidneys at the time of transplantation predicts the recipient's kidney function (allograft function) later in life.

METHODS

We retrospectively analyzed 75 consecutive adult living-donor kidney transplants performed at Kagawa University Hospital. Renal arteriosclerotic vasculopathy was defined according to the presence of fibrous intimal thickening in the interlobular artery.

RESULTS

Forty-one kidneys exhibited mild arteriosclerotic vasculopathy on preimplantation kidney biopsies. The decreases in estimated glomerular filtration rate after donation were similar in donors with or without renal arteriosclerotic vasculopathy. Pre-existing arteriosclerotic vasculopathy did not affect graft survival rate, patient survival rate or the incidence of complications. Recipients of kidneys with arteriosclerotic vasculopathy had lower allograft function at 1 and 3 years after transplantation than the recipients of arteriosclerosis-free kidneys with or without donor hypertension. In multivariate analysis, fibrous intimal thickening on preimplantation biopsy was predictive of reduced allograft function at 1 year after transplantation.

CONCLUSIONS

The present study demonstrated that mild arteriosclerotic vasculopathy in the donated kidney is an important pathological factor that reflects future impaired function of renal allografts from marginal donors.

Abnormal circadian blood pressure pattern 1-year after kidney transplantation is associated with subsequent lower glomerular filtration rate in recipients without rejection

Abnormal circadian blood pressure (BP) pattern is common after kidney transplantation but its relationship to long term allograft function is unclear. Of 119 kidney recipients who had ambulatory BP monitoring 1 year from transplantation, 36 patients without history of rejection were selected. Twenty-nine recipients were followed for 4 years and seven for 3 years. Iothalamate glomerular filtration rate (GFR) was obtained at 3 weeks then annually. Dippers (n = 10) had day-night systolic BP (SBP) drop (ΔSBP) of ≥10%, nondippers (n = 15) had ΔSBP 0%-9%, whereas reverse dippers (n = 11) had nocturnal rise in SBP. Compared with dippers, reverse and nondippers had a higher Banff cv score at 1 year (P = .03), lower GFR at last follow-up (73.7 ± 18.1, 55.7 ± 16.3, and 56.6 ± 21 mL/min/1.73 m(2) for dippers, non-, and reverse dippers, respectively, P = .05) and higher kidney function loss (8.0 ± 20, -9 ± 17, and 1 ± 14 mL/min/1.73 m(2) for dippers, non-, and reverse dippers, respectively, P = .02). GFR at 4 years and at last follow-up independently correlated with ΔSBP at 1 year (r = 0.46, P = .01; r = 0.34, P = .03). The current study indicates that abnormal circadian BP pattern at 1 year identifies a group of kidney recipients at risk for increased kidney function loss and lower GFR 3-4 years from transplantation.