The clinical usefulness of the renal allograft biopsy in the cyclosporine era: a prospective study

Renal Biopsy for Diagnosis in Kidney Disease: Indication, Technique, and Safety

Renal biopsies are the gold standard for diagnosis, staging, and prognosis of underlying parenchymal kidney disease. This article provides an overview of the current indications and highlights ways to reduce bleeding complications in order to achieve optimal diagnostic yield with minimal risk to the patient. Novel indications have emerged from the increasing use of new molecularly targeted oncologic therapies in recent years, which often induce immune-mediated renal disease. On the other hand, the detection of specific antibodies against target antigens on podocytes in the sera of patients with new-onset nephrotic syndrome has now relativized the indication for biopsy in membranous nephropathy. The use of semi-automatic spring-loaded biopsy devices and real-time ultrasound considerably declined the complication rate and is the current standard. Percutaneous renal biopsies are overall a safe procedure if contraindications are considered. A coagulation disorder needs to be excluded beforehand, and an elevated blood pressure must be reduced to the normotensive range with medications. A laparoscopic approach or a radiology interventional procedure through the internal jugular vein may be considered for obtaining a kidney tissue sample if there is an urgent indication and a bleeding tendency cannot be adequately corrected. Major bleeding after a percutaneous renal biopsy can usually be managed with selective arterial embolization of the injured renal vessel. The use of a 16-gauge needle is the most reasonable compromise between diagnostic benefit and risk of complication. In the routine diagnostic, the biopsy specimen is examined with light microscopy, immunohistochemistry, and electron microscopy. Combination with modern molecular pathology techniques will contribute to more precise insights into the development and progression of kidney disease, which will likely refine future treatments in nephrology.

Evolution of human kidney allograft pathology diagnostics through 30 years of the Banff classification process

The second half of the previous century witnessed a tremendous rise in the number of clinical kidney transplants worldwide. This activity was, however, accompanied by many issues and challenges. An accurate diagnosis and appropriate management of causes of graft dysfunction were and still are, a big challenge. Kidney allograft biopsy played a vital role in addressing the above challenge. However, its interpretation was not standardized for many years until, in 1991, the Banff process was started to fill this void. Thereafter, regular Banff meetings took place every 2 years for the past 30 years. Marked changes have taken place in the interpretation of kidney allograft biopsies, diagnosis, and classification of rejection and other non-rejection pathologies from the original Banff 93 classification. This review attempts to summarize those changes for increasing the awareness and understanding of kidney allograft pathology through the eyes of the Banff process. It will interest the transplant surgeons, physicians, pathologists, and allied professionals associated with the care of kidney transplant patients.

Utility of interval kidney biopsy in ANCA-associated vasculitis

OBJECTIVES

ANCA-associated vasculitis (AAV) is a rare autoimmune disorder that commonly involves the kidney. Early identification of kidney involvement, assessing treatment-response and predicting outcome are important clinical challenges. Here, we assessed the potential utility of interval kidney biopsy in AAV.

METHODS

In a tertiary referral centre with a dedicated vasculitis service, we identified patients with AAV who had undergone interval kidney biopsy, defined as a repeat kidney biopsy (following an initial biopsy showing active AAV) undertaken to determine the histological response in the kidney following induction immunosuppression. We analysed biochemical, histological and outcome data, including times to kidney failure and death for all patients.

RESULTS

We identified 57 patients with AAV who underwent at least one interval kidney biopsy (59 interval biopsies in total; median time to interval biopsy ∼130 days). Of the 59 interval biopsies performed, 24 (41%) patients had clinically suspected active disease at time of biopsy which was confirmed histologically in only 42% of cases; 35 (59%) patients were in clinical disease-remission, and this was correct in 97% of cases. The clinician's impression was incorrect in one in four patients. Hematuria at interval biopsy did not correlate with histological activity. Interval biopsy showed fewer acute lesions and more chronic damage compared with initial biopsy and led to immunosuppressive treatment-change in 75% (44/59) of patients. Clinical risk prediction tools tended to operate better using interval biopsy data.

CONCLUSION

Interval kidney biopsy is useful for determining treatment-response and subsequent disease management in AAV. It may provide better prognostic information than initial kidney biopsy and should be considered for inclusion into future clinical trials and treatment protocols for patients with AAV.

Biopsy findings after detection of de novo donor-specific antibodies in renal transplant recipients: a single center experience

Background

De novo donor-specific antibodies (DSA) are associated with an increased risk of antibody-mediated rejection and a substantial reduction of allograft survival. We hypothesized that detection of DSA should prompt a biopsy even in the absence of proteinuria and loss of estimated glomerular filtration rate (eGFR). However, data on a population without proteinuria or loss of kidney function is scant, and this is the main novelty of our study design.

Methods

Single center retrospective analysis on biopsy findings after detection of de novo DSA. One-hundred-thirty-two kidney and pancreas-kidney transplant recipients were included. Eighty-four of these patients (63.6%) underwent allograft biopsy. At the time of biopsy n = 50 (59.5%) had a protein/creatinine ratio (PCR) > 300 mg/g creatinine and/or a loss of eGFR ≥ 10 ml/min in the previous 12 months, whereas 40.5% did not. Diagnosis of rejection was performed according to Banff criteria.

Results

Seventy-seven (91.7%) of the biopsies had signs of rejection (47.6% antibody mediated rejection (ABMR), 13.1% cellular, 20.2% combined, 10.7% borderline). Among subjects without proteinuria or loss of eGFR ≥ 10 ml/min/a (n = 34), 29 patients (85.3%) showed signs of rejection (44.1% antibody mediated (ABMR), 14.7% cellular, 11.8% combined, 14.7% borderline).

Conclusion

The majority of subjects with de novo DSA have histological signs of rejection, even in the absence of proteinuria and deterioration of graft function. Thus, it appears reasonable to routinely perform an allograft biopsy after the detection of de novo DSA.

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s40620-021-01040-y.

Pathology of the kidney allograft

The kidney biopsy still represents the best approach to diagnose renal transplant complications. It is considered the gold standard in the diagnosis of rejection and non-rejection complications. Although invasive, it is a safe procedure with a very low complication rate. With adequate sampling, changes related to antibody-mediated rejection (ABMR) and T-cell mediated rejection (TCMR) can be identified. However, the pathologist needs to be aware of the many other complications, not related to rejection, that can affect the allograft function. Examples include viral infections, drug toxicity, systemic diseases such as hypertension and diabetes, and recurrent or de novo glomerulopathy, among others. In this article, we review the recent classification of pathology of the kidney allograft, with reference to recent consensus reached at the most recent Banff renal allograft classification meetings, and also highlight common non-rejection complications of the kidney transplant.

A label-free approach by infrared spectroscopic imaging for interrogating the biochemistry of diabetic nephropathy progression

Routine histology, the current gold standard, involves staining for specific biomolecules. However, untapped biochemical information in tissue can be gathered using biochemical imaging. Infrared spectroscopy is an emerging modality that allows label-free chemical imaging to derive biochemical information (such as protein, lipids, DNA, collagen) from tissues. Here we employed this technology in order to better predict the development of diabetic nephropathy. Using human primary kidney biopsies or nephrectomies, we obtained tissue from 4 histologically normal kidneys, 4 histologically normal kidneys from diabetic subjects, and 5 kidneys with evidence of diabetic nephropathy. A biochemical signature of diabetic nephropathy was derived that enabled prediction of nephropathy based on the ratio of only 2 spectral frequencies. Nonetheless, using the entire spectrum of biochemical information, we were able to detect renal disease with near-perfect accuracy. Additionally, study of sequential protocol biopsies from 3 transplanted kidneys showed biochemical changes even prior to clinical manifestation of diabetic nephropathy. Thus, infrared imaging can identify critical biochemical alterations that precede morphologic changes, potentially allowing for earlier intervention.

The significance of histological diagnosis in renal allograft biopsies in 2014

In 2014, the renal allograft biopsy still represents the best available diagnostic 'gold' standard to assess reasons for allograft dysfunction. However, it is well recognized that histological lesion observed in the biopsy is of limited diagnostic specificity and that the Banff classification as the international diagnostic standard represents mere expert consensus. Here, we review the role of the renal allograft biopsy in different clinical and diagnostic settings. To increase diagnostic accuracy and to compensate for lack of specificity, the interpretation of biopsy pathology needs to be within the clinical context, primarily defined by time post-transplantation and patient-specific risk profile. With this in mind, similar histopathological patterns will lead to different conclusions with regard to diagnosis, disease grading and staging and thus to patient-specific clinical decision-making. Consensus generation for such integrated diagnostic approach, preferably including new molecular tools, represents the next challenge to the transplant community on its way to precision medicine in transplantation.

Urinary cell mRNA profiles and differential diagnosis of acute kidney graft dysfunction

Noninvasive tests to differentiate the basis for acute dysfunction of the kidney allograft are preferable to invasive allograft biopsies. We measured absolute levels of 26 prespecified mRNAs in urine samples collected from kidney graft recipients at the time of for-cause biopsy for acute allograft dysfunction and investigated whether differential diagnosis of acute graft dysfunction is feasible using urinary cell mRNA profiles. We profiled 52 urine samples from 52 patients with biopsy specimens indicating acute rejection (26 acute T cell-mediated rejection and 26 acute antibody-mediated rejection) and 32 urine samples from 32 patients with acute tubular injury without acute rejection. A stepwise quadratic discriminant analysis of mRNA measures identified a linear combination of mRNAs for CD3ε, CD105, TLR4, CD14, complement factor B, and vimentin that distinguishes acute rejection from acute tubular injury; 10-fold cross-validation of the six-gene signature yielded an estimate of the area under the curve of 0.92 (95% confidence interval, 0.86 to 0.98). In a decision analysis, the six-gene signature yielded the highest net benefit across a range of reasonable threshold probabilities for biopsy. Next, among patients diagnosed with acute rejection, a similar statistical approach identified a linear combination of mRNAs for CD3ε, CD105, CD14, CD46, and 18S rRNA that distinguishes T cell-mediated rejection from antibody-mediated rejection, with a cross-validated estimate of the area under the curve of 0.81 (95% confidence interval, 0.68 to 0.93). Incorporation of these urinary cell mRNA signatures in clinical decisions may reduce the number of biopsies in patients with acute dysfunction of the kidney allograft.

Utility of renal biopsy in the clinical management of renal disease

Characterizing chronic kidney disease (CKD) at all stages is an essential part of rational management and the renal biopsy plays a key role in defining the processes involved. There remain no global guidelines available to the renal community on indications for this important diagnostic, prognostic, and relatively safe test. Although most nephrologists recognize several clear indications for a renal biopsy, it is still underutilized. It not only helps the clinician to manage the patient with CKD, but it can also help clarify the epidemiology of CKD, and aid research into the pathobiology of disease with the aim of discovering new therapies. It may be useful for instance in elderly patients with CKD, those with diabetes and presumed 'hypertensive nephropathy', and in some patients with advanced CKD as part of the pretransplant work-up. In some populations (for example, immunoglobulin A nephropathy and ANCA vasculitis), renal biopsy allows disease classification that may predict CKD progression and response to therapy. For the individual, interval renal biopsy may be of use in providing ongoing therapeutic and prognostic information. Molecular advances will change the landscape of renal pathology and add a new dimension to the diagnostic precision of kidney biopsy. Organizing the multiplicity of information available in a renal biopsy to maximize benefits to the patient, as well as to the epidemiologist and researcher, is one of the challenges that face the nephrology community.

Electron microscopy in determining the etiology of kidney allograft dysfunction

BACKGROUND

Biopsy of the transplanted kidney serves a definitive role in elucidating the possible causes of allograft dysfunction. At our transplant clinic we have observed that electron microscopy (EM) does not usually refine the findings initially disclosed by light microscopy with direct immunofluorescence (LM).

METHODS

We studied whether EM results differ from or add to LM results. We compared the reports of 65 allograft biopsies performed on 60 patients over 82 consecutive weeks. We classified biopsy interpretations by 15 possible diagnoses and categorically by glomerular versus nonglomerular disease. We determined agreement between LM and EM reports by Cohen's kappa statistic, and applied the McNemar test to determine whether EM interpretation yielded significantly more glomerular diagnoses on the same biopsy samples.

RESULTS

There was strong agreement (kappa, 0.94: 95% confidence interval [CI], 0.88-1.00), between the EM- and LM-based interpretations. EM did not detect more glomerular disease than LM (discordance rate, 4.6%: 95% CI, -1.92% to 4.62%: P = .25). EM did not add to the diagnosis of rejection. EM described 3 additional cases of transplant glomerulopathy, but did not lead in a change in management of kidney allograft dysfunction.

CONCLUSION

Electron microscopy, used routinely, does not add to light microscopy in the evaluation of kidney transplant dysfunction.

Clinical role of the renal transplant biopsy

Percutaneous needle core biopsy is the definitive procedure by which essential diagnostic and prognostic information on acute and chronic renal allograft dysfunction is obtained. The diagnostic value of the information so obtained has endured for over three decades and has proven crucially important in shaping strategies for therapeutic intervention. This Review provides a broad outline of the utility of performing kidney graft biopsies after transplantation, highlighting the relevance of biopsy findings in the immediate and early post-transplant period (from days to weeks after implantation), the first post-transplant year, and the late period (beyond the first year). We focus on how biopsy findings change over time, and the wide variety of pathological features that characterize the major clinical diagnoses facing the clinician. This article also includes a discussion of acute cellular and humoral rejection, the toxic effects of calcineurin inhibitors, and the widely varying etiologies and characteristics of chronic lesions. Emerging technologies based on gene expression analyses and proteomics, the in situ detection of functionally relevant molecules, and new bioinformatic approaches that hold the promise of improving diagnostic precision and developing new, refined molecular pathways for therapeutic intervention are also presented.

MicroRNA profiles in allograft tissues and paired urines associate with chronic allograft dysfunction with IF/TA

Despite the advances in immunosuppression, renal allograft attrition over time remains unabated due to chronic allograft dysfunction (CAD) with interstitial fibrosis (IF) and tubular atrophy (TA). We aimed to evaluate microRNA (miRNA) signatures in CAD with IF/TA and appraise correlation with paired urine samples and potential utility in prospective evaluation of graft function. MiRNA signatures were established between CAD with IF/TA versus normal allografts by microarray. Validation of the microarray results and prospective evaluation of urine samples was performed using real-time quantitative-PCR (RT-qPCR). Fifty-six miRNAs were identified in samples with CAD-IF/TA. Five miRNAs were selected for further validation based on array fold change, p-value and in silico predicted mRNA targets. We confirmed the differential expression of these five miRNAs by RT-qPCR using an independent set of samples. Differential expression was detected for miR-142-3p, miR-204, miR-107 and miR-211 (p < 0.001) and miR-32 (p < 0.05). Furthermore, differential expression of miR-142-3p (p < 0.01), miR-204 (p < 0.01) and miR-211 (p < 0.05) was also observed between patient groups in urine samples. A characteristic miRNA signature for IF/TA that correlates with paired urine samples was identified. These results support the potential use of miRNAs as noninvasive markers of IF/TA and for monitoring graft function.

Identification of lesions indicating rejection in kidney transplant biopsies: tubulitis is severely under-detected by conventional microscopy

BACKGROUND

In the current international Banff classification of kidney transplant rejection, tubulitis and intimal arteritis are regarded as the key histological features of acute rejection. Grade 1 tubulitis can sometimes be seen in biopsies that do not represent acute rejection; but in the case of intimal arteritis, just one lymphocyte can justify anti-rejection treatment. Our aim was to audit reliability and accuracy of recognizing tubulitis and intimal arteritis using the approach recommended by the Banff classification and correlate any discrepancies with subsequent graft function.

METHODS

This is a retrospective review of all kidney transplant biopsies reported as negative for rejection from 1 January 2009 to 31 December 2009 to assess the presence or absence of occult tubulitis and arteritis. Lymphocytes were immunostained with CD3, using Periodic Acid Schiff as a counterstain. Sections were reviewed to detect missed intimal arteritis and tubulitis. Discrepancies between the report and the immunostain results were analysed by biopsy type and broken down by the reporting pathologist. The graft function of any patient with missed lesions was checked to test for adverse impact on the patient.

RESULTS

'Missed' tubulitis was found in 68% of biopsies, but only two such cases subsequently developed biopsy-proven acute rejection. Only one case of missed intimal arteritis was found (1%) and the subsequent clinical course suggested that this was probably early rejection. There was no significant difference between the reporting pathologists.

CONCLUSIONS

We conclude that tubulitis is missed very frequently, but the Banff classification seems to be 'calibrated' to allow for this and it does not seriously affect the identification of clinically significant acute rejection. Immunostaining is therefore not indicated in routine practice because (by Banff criteria) it would result in over-diagnosis of rejection. Intimal arteritis can indicate acute rejection even if extremely mild.

Identifying biomarkers as diagnostic tools in kidney transplantation

There is a critical need for biomarkers for early diagnosis, treatment response, and surrogate end point and outcome prediction in organ transplantation, leading to a tailored and individualized treatment. Genomic and proteomic platforms have provided multiple promising new biomarkers during the last few years. However, there is still no routine application of any of these markers in clinical transplantation. This article will discuss the existing gap between biomarker discovery and clinical application in the kidney transplant setting. Approaches to implementing biomarker monitoring into clinical practice will also be discussed.

Biomarkers for early and late stage chronic allograft nephropathy by proteogenomic profiling of peripheral blood

Background

Despite significant improvements in life expectancy of kidney transplant patients due to advances in surgery and immunosuppression, Chronic Allograft Nephropathy (CAN) remains a daunting problem. A complex network of cellular mechanisms in both graft and peripheral immune compartments complicates the non-invasive diagnosis of CAN, which still requires biopsy histology. This is compounded by non-immunological factors contributing to graft injury. There is a pressing need to identify and validate minimally invasive biomarkers for CAN to serve as early predictors of graft loss and as metrics for managing long-term immunosuppression.

Methods

We used DNA microarrays, tandem mass spectroscopy proteomics and bioinformatics to identify genomic and proteomic markers of mild and moderate/severe CAN in peripheral blood of two distinct cohorts (n = 77 total) of kidney transplant patients with biopsy-documented histology.

Findings

Gene expression profiles reveal over 2400 genes for mild CAN, and over 700 for moderate/severe CAN. A consensus analysis reveals 393 (mild) and 63 (moderate/severe) final candidates as CAN markers with predictive accuracy of 80% (mild) and 92% (moderate/severe). Proteomic profiles show over 500 candidates each, for both stages of CAN including 302 proteins unique to mild and 509 unique to moderate/severe CAN.

Conclusions

This study identifies several unique signatures of transcript and protein biomarkers with high predictive accuracies for mild and moderate/severe CAN, the most common cause of late allograft failure. These biomarkers are the necessary first step to a proteogenomic classification of CAN based on peripheral blood profiling and will be the targets of a prospective clinical validation study.

Neutrophilic tubulitis as a marker for urinary tract infection in renal allograft biopsies with C4d deposition

BACKGROUND

Neutrophilic tubulitis accompanied by intratubular neutrophil clusters in the renal allograft is a surrogate marker for urinary tract infection (UTI). Overlapping histologic findings can occur in antibody-mediated rejection, which is characterized by peritubular capillary (PTC) deposition of C4d. This study evaluated the incidence of UTI in biopsies with concurrent neutrophilic tubulitis and PTC C4d staining.

METHODS

Thirty-three allograft biopsies from 27 patients selected for the presence of simultaneous C4d staining and neutrophilic tubulitis were correlated with urine culture (U/C) results.

RESULTS

U/C obtained on the same day as the biopsy confirmed UTI in 13 of 33 (39%) biopsies. Among 20 patients with negative U/C; prior culture results within 10 days of the biopsy were available for nine patients, and 5 of 9 (55%) were positive. Thus, UTI was confirmed in 18 of 33 (54%) biopsies. Biopsy interpretation and clinical management was confounded by changes of concurrent acute cellular rejection and antibody-mediated rejection confirmed by demonstration of donor-specific antibodies. Combined therapy with antibiotics and antirejection medications (ART) was administered to 12 of 18 (67%) patients.

CONCLUSIONS

Neutrophilic tubulitis accompanied by neutrophil clusters in the tubular lumen is a useful marker of UTI, even in the presence of PTC C4d deposition. Therapeutic response to antibiotics is limited by co-existent T-cell or antibody-mediated rejection and underlying chronic allograft nephropathy.

Choice of test for association in small sample unordered r x c tables

Pearson's chi-squared, the likelihood-ratio, and Fisher-Freeman-Halton's test statistics are often used to test the association of unordered r x c tables. Asymptotical, exact conditional, or exact conditional with mid-p adjustment methods are commonly used to compute the p-value. We have compared test power and significance level for these test statistics and p-value calculations in small sample r x c tables, mostly 3 x 2 and some with both r and c are greater than 2. After extensive simulations, in general we recommend using an exact conditional mid-p test with Pearson's chi-squared or Fisher-Freeman-Halton's statistic, which usually is the most powerful test yet preserve the approximate significance level. Moreover, we recommend that the asymptotic Pearson's chi-squared or other asymptotic tests not be used for small sample r x c tables.

Evaluation of hepatocyte growth factor as a sensitive marker for early detection of acute renal allograft rejection

BACKGROUND

It has been shown that hepatocyte growth factor (HGF), besides its well-established hepatotrophic effect in liver regeneration, is involved in the regeneration of the kidney after injury. In the present study we investigated whether HGF can serve as a marker for detection of acute rejection in the early posttransplantation period.

METHODS

HGF levels were determined in pre- and posttransplant sera (up to day 21) of 26 recipients with biopsy-proven acute rejection, 30 recipients with acute tubular necrosis (ATN), and 32 recipients without posttransplant complications.

RESULTS

Although no association was found between pretransplant HGF and death-censored functional graft survival, receiver operating characteristic (ROC) curves demonstrated that HGF measured during the entire posttransplant study period, and especially on days 3 to 5, was a good marker for differentiating recipients who subsequently developed acute rejection from recipients with an uncomplicated course (P<0.0001, specificity 87%, sensitivity 84%). HGF measured from day 3 until day 21 posttransplantation, and especially on days 7 to 9, was also a sensitive marker for differentiating recipients with ATN from recipients with an uncomplicated course (P<0.0001). If considered in combination with sCD30, the diagnostic value of HGF was further improved. While 73% of samples from patients with impending rejection were positive for both HGF and sCD30, 94% of samples from nonrejecting patients were double-negative and none of the samples from this group fell into the double-positive category (P<0.0001).

CONCLUSIONS

Our data suggest that HGF measured during the early posttransplant period might be a useful parameter for early detection of acute renal allograft rejection.

Biomarkers and surrogate endpoints in renal transplantation: present status and considerations for clinical trial design

Of major importance in clinical trials is the ability to predict individual patient outcome or endpoints using biomarkers, also known as variables or predictors, in as safe, efficient, and accurate a manner as possible. This review addresses the concepts and possible strategies for use of predictor and surrogate biomarkers in the design of clinical trials in renal transplantation. The statistical concepts apply equally well to other organ grafts.

Advances in pre- and posttransplant immunologic testing in kidney transplantation

Pre- and posttransplant risk estimation in kidney transplantation is important for the selection of appropriate treatment strategies. Recently, using new immunologic tests, we made observations within the framework of the Collaborative Transplant Study that may influence clinical practice. Complement-dependent lymphocytotoxic panel reactivity as a measure of anti-HLA sensitization, although criticized for its low sensitivity, is a useful indicator of an increased risk of rejection. Using the more sensitive complement-independent ELISA methodology, which utilizes solubilized HLA molecules instead of lymphocytes, we found that recipients with preformed complement-dependent anti-HLA antibodies showed a decreased graft survival only if their antibodies were directed against both HLA class I and class II, whereas isolated reactivity only against HLA class I or class II was of no clinical consequence. Pretransplant serum-soluble CD30 (sCD30) was found to be an independent and highly predictive factor of immunologic risk. The effects of sCD30 and anti-HLA antibodies were additive. Importantly, even patients without anti-HLA antibodies showed a strong HLA matching effect if their pretransplant serum contained high levels of sCD30. Although the role of anti-HLA antibody formation after transplantation remains uncertain, ELISA-detected sCD30 was shown to indicate impending graft rejection as early as on posttransplant days 3 to 5. Another very sensitive indicator of impending rejection is provided by posttransplant monitoring of the cytotoxic T-lymphocyte effector genes, perforin and granzyme B, in peripheral blood using real-time PCR.

Impact of acute rejection episodes on long-term graft survival following simultaneous kidney-pancreas transplantation

Although it is well established that acute rejection is one of the major risk factors for chronic graft loss following kidney transplantation, its effect on long-term graft survival following simultaneous kidney-pancreas transplants (SKPTs) is less well known. We analyzed a large cohort of SKPTs and cadaver kidney transplants reported to the United Network for Organ Sharing database during 1988-97, to determine the impact of acute rejection episodes on long-term kidney and pancreas graft survival. Only patients whose kidney and pancreas grafts had survived for at least 1 year were included. Other potential risk factors influencing long-term graft survival were included in the analysis. Of the 4251 SKPTs, 45% had no acute rejection, 36% had kidney only rejection, 3% had pancreas only rejection, and 16% had both kidney and pancreas rejection within the 1st year post transplant. The 5-year kidney and pancreas graft survival rates adjusted for other risk factors were 91% and 85%, respectively; for those with no acute rejection episodes, 88% and 84%, respectively; for those with kidney only rejection, 94% and 83%, respectively; for those with pancreas only rejection; and 86% and 78%, respectively, for those with both kidney and pancreas rejection. The relative risk (RR) of kidney graft failure was 1.32 when acute rejection involved the kidney graft only, while the RR was 1.53 when the rejection involved both organs. We conclude that acute rejection episodes have a negative impact on the long-term kidney graft survival in the SKPT population similar to that in the cadaver kidney transplant population. Patients who had acute rejection episodes of both kidney and pancreas have the worst long-term graft survival.

Occurrence of urinary tract infection in patients with renal allograft biopsies showing neutrophilic tubulitis

Lymphocytic tubulitis is a well-accepted criterion for acute cellular rejection in renal allograft biopsies. Neutrophilic tubulitis has been used as a surrogate marker for urinary tract infection, but it is not clear how reliably this lesion can be used to make this diagnosis. Biopsy findings were correlated with clinical features in 26 renal allograft biopsies with interstitial polymorphonuclear infiltrates associated with neutrophilic tubulitis. The grade of neutrophilic tubulitis exceeded the grade of lymphocytic tubulitis in 7 (44%) of 16 patients with, but in only 0 patients without, a positive urine culture. Culture confirmed urinary tract infection in 16 (62%) of 26 patients. It is possible that prior antibiotic therapy led to a false-negative culture and masked the diagnosis in two additional patients. Lymphocytic tubulitis made it difficult to exclude concurrent acute cellular rejection in all biopsies studied. In 6 (23%) of 26 patients, negative cultures and response to steroid treatment confirmed that neutrophilic tubulitis can occur in biopsies without urinary tract infection. The relative contributions of infection and rejection could not be determined in patients treated with both steroids and antibiotics. Neutrophilic tubulitis in a renal allograft biopsy should alert the clinician to the possibility of urinary tract infection, even if concurrent lymphocytic tubulitis is present. Confirmation by urine culture is needed because biopsies with ischemic injury and acute cellular or antibody-mediated rejection can show overlapping histology.

Evaluation of posttransplantation soluble CD30 for diagnosis of acute renal allograft rejection

BACKGROUND

Posttransplantation measurement of soluble CD30 (sCD30) may be useful for identifying kidney graft recipients at risk of impending graft rejection in the early posttransplantation period.

METHODS

We measured plasma sCD30 levels and evaluated the levels in relation to the diagnosis of rejection.

RESULTS

Receiver operating characteristic curves demonstrated that on posttransplantation days 3 to 5, sCD30 allowed a differentiation of recipients who subsequently developed acute allograft rejection (n=25) from recipients with an uncomplicated course (n=20, P<0.0001) (area under the receiver operating characteristic curve 0.96, specificity 100%, sensitivity 88%) and recipients with acute tubular necrosis in the absence of rejection (n=11, P=0.001) (area under the receiver operating characteristic curve 0.85, specificity 91%, sensitivity 72%).

CONCLUSIONS

sCD30 measured on posttransplantation days 3 to 5 offers a noninvasive means for differentiating patients with impending acute allograft rejection from patients with an uncomplicated course or with acute tubular necrosis.

The impact of late acute rejection after cadaveric kidney transplantation

BACKGROUND

Acute graft rejection (AR) following renal transplantation results in reduced graft survival. However, there is uncertainty regarding the definition, aetiology and long-term graft and patient outcome of AR occurring late in the post-transplant period.

AIM

To determine if rejection episodes can be classified by time from transplantation by their impact on graft survival into early acute rejection (EAR) and late acute rejection (LAR).

MATERIALS AND METHODS

687 consecutive adult renal transplant recipients who received their first cadaveric renal transplant at a single centre. All received cyclosporine (CyA)-based immunosuppression, from 1984 to 1996, with a median follow-up of 6.9 yr. Details were abstracted from clinical records, with emphasis on age, sex, co-morbid conditions, HLA matching, rejection episodes, patient and graft survival.

ANALYSIS

Patients were classified by the presence and time to AR from the date of transplantation. Using those patients who had no AR (NAR) as a baseline, we determined the relative risk of graft failure by time to rejection. The characteristics of patients who had no rejection, EAR and LAR were compared.

RESULTS

Compared with NAR, the risk of graft failure was higher for those patients who suffered a rejection episode. A much higher risk of graft failure was seen when the first rejection episode occurred after 90 d. Thus, a period of 90 d was taken to separate EAR and LAR (relative risk of 3.06 and 5.27 compared with NAR as baseline, p<0.001). Seventy-eight patients (11.4%) had LAR, 271 (39.4%) had EAR and 338 (49.2%) had NAR. The mean age for each of these groups differed (LAR 39.6 yr, EAR 40.8 yr compared with NAR 44 yr, p<0.003). The 5-yr graft survival for those who had LAR was 45% and 10-yr survival was 28%. HLA mismatches were more frequent in those with EAR vs. NAR (zero mismatches in HLA-A: 36 vs. 24%, HLA-B: 35 vs. 23% and HLA-DR: 63 vs. 41%, p<0.003). There was no difference in mismatching frequency between NAR and LAR.

CONCLUSIONS

AR had a deleterious impact on graft survival, particularly if occurring after 90 d. AR episodes should therefore be divided into early and late phases. In view of the very poor graft survival associated with LAR, it is important to gain further insight into the main aetiological factors. Those such as suboptimal CyA blood levels and non-compliance with medication should be further investigated with the aim of developing more effective immunosuppressive regimens in order to reduce the incidence of LAR.

Histopathology of a human allografted kidney with clinically sufficient function

To clarify the clinico-pathological significance of protocol biopsy and clinically silent rejection in the management of renal graft recipients, we selected a total of 139 (23%) from 604 biopsy specimens according to the following criteria: 1) less than 1.4 mg/dL of serum creatinine and 2) more than 1,500 mL/d of urine volume at time of biopsy. Clinical indications for the biopsy were classified into five categories: i) protocol biopsy (73 specimens), including 69 cases at discharge post-transplantation; ii) slight increase in serum creatinine (32); iii) proteinuria (20); iv) evaluation of pulse-therapy (13); and v) fever elevation (1). Except for the last category, the specimens were histopathologically diagnosed as being normal in 50 (68%), 6 (17%), 1 (5%), and 5 (38%) specimens, respectively. Even borderline changes, and mild acute rejection, as well as drug-induced nephropathy were included, implying the existence of clinically silent rejection or drug-induced nephropathy. Obvious diversity in the histopathological diagnosis was noted in category iii) showing proteinuria, which was mainly caused by chronic rejection, drug-induced nephropathy and glomerulonephritis. The graft survival rate was no different among the four categories, except for category v). These results indicate that biopsies obtained from functionally sufficient renal grafts could provide useful information in the management of the recipients. The clinical significance of protocol biopsy awaits further clarification by the analysis of a large number of cases.

Pharmacoeconomics of therapeutic drug monitoring in transplantation

Immunosuppressive drugs have contributed significantly to the success of organ transplantation. Therapeutic drug monitoring is an integral part of transplant protocols. However, there is little information concerning its positive contribution to pharmacoeconomics. Before developing studies to demonstrate the potential benefits of TDM, consideration must be given to the type of TDM to be evaluated. It is argued that, given that the lymphocyte in the central compartment is the target for immunosuppressants, Area-Under-the-Curve monitoring may be a better reflection of control and toxicity than traditional trough monitoring.

Diagnostic techniques in the work-up of renal allograft dysfunction--an update

After renal transplantation, acute allograft dysfunction secondary to acute rejection occurs in around 30-40% of patients. Although in the majority of patients these episodes are reversible, acute rejection remains a major risk factor for the development of chronic rejection. Remarkably, prior episodes of acute allograft rejection are associated with decreased allograft survival. Histologic examination of the percutaneous core needle transplant biopsy remains the gold standard for the diagnosis of acute rejection. It does, however, have a number of shortcomings, and less invasive procedures that could diagnose incipient rejection and simultaneously provide mechanistic information on the rejection process (allowing delivery of more tailored therapy) are being sought. To address these problems a number of alternative diagnostic procedures have been suggested, including duplex Doppler ultrasound assessment, fine-needle aspiration biopsy, urine cytology, urine cytokine analysis, serum cytokine analysis, and cytokine analysis of biopsy material.