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Volume: 15 Issue: 1 February 2017 - Supplement - 1

FULL TEXT

Evaluation of Indication Biopsies ≥ 5 Years After Kidney Transplant: A Single-Center Experience

Objectives: Rejection is a common cause of late graft dysfunction seen on biopsy studies. The aim of this study was to evaluate indication biopsy findings ≥ 5 years after kidney transplant and to assess the effectiveness of applied treatments.

Materials and Methods: Between January 2013 and December 2015, 30 patients who underwent renal transplant indication biopsies and were followed up for ≥ 6 months were evaluated retrospectively. A > 30% increase in serum creatinine and/or develop­ment of > 1 g/day proteinuria was considered an acceptable indication for biopsy.

Results: Of the 156 indication biopsies obtained within a 3-year period, 30 of them were indication biopsies performed ≥ 5 years after transplant. Twenty patients (67%) demonstrated late graft rejection, 6 patients (20%) had recurrent or de novo glo­merulonephritis, and 4 patients (13%) were diagnosed with idiopathic chronic allograft nephropathy. The mean total histologic score was 6.2 ± 2.6, and the chronicity rate was 70%. For patients with late rejection, treatment consisted of pulse steroids in 11, intravenous immuno­globulin in 5, plasmapheresis in 4, antithymocyte globulin in 3, and rituximab in 2 cases. Five patients with glomerulonephritis received pulse steroids, 1 received rituximab therapy, and 3 were treated with cyclophosphamide. The mean follow-up after indi­cation biopsy was 16 ± 11 months. Eleven patients (37%) had a progressive disease course and 7 patients (23%) resumed hemodialysis. Of the 30 patients, the 15 whose glomerular filtration rate was < 30 mL/min/1.72 m2 at biopsy were more likely to have a progressive disease course (53% vs. 20%; P = .05) and more com­monly resumed dialysis (40% vs. 7%; P = .03).

Conclusions: Rejection was the most common cause of graft dysfunction long term. Chronic histologic changes predominated in indication biopsies ≥ 5 years posttransplant. Regardless of diagnosis, a low glo­merular filtration rate at biopsy was closely associated with poor renal outcomes.


Key words : Chronic rejection, Graft failure, Kidney biopsy, Kidney transplantation, Late graft dysfunction, Recurrent glomerulonephritis

Introduction

Developments in transplant immunology and immunosuppressive drugs have greatly improved graft and patient outcomes in the early stages following kidney transplant. However, this effect on survival does not persist in the long term. In large-scale data from Europe, the first-year graft survival rate was up to 90% but gradually diminished to 70% and 50% in years 5 and 10 after transplant.1 As indicated by kidney biopsy studies, chronic graft rejection is the most common cause of graft loss in the long term, and the effectiveness of any given treatment during this period is controversial.2-5 Similarly, de novo or recurrent glomerulonephritis that occurs early or late after kidney transplant plays a significant role in graft loss.5,6 Today, there is still no consensus as to the optimal follow-up and treatment strategies for these patients. The aim of this study was to evaluate indication biopsy (IB) findings 5 years after kidney transplant and to investigate the effectiveness of the treatments applied.

Materials and Methods

Between January 2013 and December 2015, kidney transplant patients who had completed their fifth year posttransplant and who had a current IB and postbiopsy follow-up lasting ≥ 6 months were evaluated retrospectively. The IB was performed on all patients who presented with a > 30% increase in serum creatinine and/or developed > 1 g/day proteinuria. According to the Banff classification system, a total biopsy score ≥ 5 was interpreted to signify chronic allograft nephropathy (CAN). Early response to treatment after IB was defined as a ≥ 30% decrease in serum creatinine and/or a ≥ 50% reduction in daily proteinuria. Gradual and persistent increases in serum creatinine level after IB were interpreted as a progressive disease course. Estimated glomerular filtration rate (eGFR) was calculated using the Modification of Diet in Renal Disease formula.

Renal histology
Protocol biopsies and IBs are routine practices in our unit. To perform them, specimens were fixed in 4% formalin and then processed. Paraffin sections were stained with hematoxylin and eosin stain, periodic acid-Schiff stain, Mason’s trichrome stain, Jones methenamine silver, and if necessary, Van Gieson’s stain for visualizing elastic fibers and Congo red. Each specimen was examined using light microscopy and direct immunofluorescence (for bound immuno­globulin IgG, IgA, IgM, complement C3, C1q, fibrinogen, and kappa and lambda light chains). Specimens having > 10 glomeruli and an artery were considered sufficient for evaluation and were assessed by a single nephropathologist. The existence of global glomerular sclerosis (ggs), interstitial fibrosis (ci) and tubular atrophy (ct), interstitial inflammation (i), vascular intimal fibrosis (cv), and arteriolar hyalinosis (ah) were recorded.

Findings were semiquantitatively graded on a scale of 0 to 3 according to severity. Glomerulo­sclerosis scores were denominated as 0, 1 (≤ 20%), 2 (20%-59%), and 3 (> 59%) according to the percentage of ggs and ci, ct, cv, i, and ah, defined according to the Banff 2009 meeting report standards.7 The chronicity index was calculated from the sum of these scores (gss+ci+ct+i+cv+ah) and a value of ≥ 5 was interpreted as indicating CAN.

Statistical analyses
Data were expressed as means ± standard deviation. Proportions were compared using chi-square analysis. The mean values of 2 groups were compared using the t test or a nonparametric test if the data were not normally distributed. A P value < .05 was considered significant. All statistical analyses were performed using SPSS software for Windows (version 15.0, SPSS Inc., Chicago, IL, USA).

Results

Of the 156 IBs obtained within a 3-year period, 30 of them were IBs performed ≥ 5 years after transplant in 30 patients. These cases constituted the study group. The average time to posttransplant IB was 98 ± 31 months (range, 60-154 mo). The mean age of patients was 35 ± 11 years, and the female-to-male ratio was 1:2. At baseline, year 1, year 3, and at biopsy time mean serum creatinine levels were 1.1 ± 0.2 mg/dL, 1.3 ± 0.4 mg/dL, 1.4 ± 0.4 mg/dL, and 2.5 ± 1.1 mg/dL respectively. The amount of proteinuria at biopsy averaged 1.7 ± 1.6 g/day. At year 1 posttransplant, 16% of the patients had a history of graft rejection.

Renal biopsy was performed because of graft dysfunction in 11 (36.7%), proteinuria in 5 (16.6%), and graft dysfunction accompanied by proteinuria in 14 cases (46.7%). Twenty patients (66.7%) de­monstrated late graft rejection, 6 (20%) had recurrent or de novo glomerulonephritis and 4 patients (13.3%) were diagnosed with idiopathic CAN. Of the 20 patients with graft rejection, 10 patients (50%) had features of acute type rejection, 3 patients (15%) had mixed rejection, and 16 patients (80%) had C4d positivity. Histologic features indicating CAN were present in 20 of the biopsies (66.7%).

Outcome of patients with graft rejection
Of the 20 patients with graft rejection, treatment consisted of pulse steroids (prednol L) in 11, intra­venous immunoglobulin with a cumulative dose of 1 to 2 g/kg in 5, plasmapheresis in 4, antithymocyte globulin in 3, and rituximab in 2 cases. Maintenance immunosuppressive therapy invariably consisted of tacrolimus plus mycophenolic acid in this group.

The mean serum creatinine levels of these patients during IB, at discharge, at month 6, and at last follow-up (range, 16 ± 11 mo) were 2.6 ±1.2 mg/dL (range, 1.1-6.3), 2.4 ± 0.8 mg/dL (range, 1.1-4.9), 2.7 ± 1.5 mg/dL (range, 1.1-7.3), and 3.0 ± 2.5 mg/dL (range, 0.9-11.0). Total histologic score was high (chronicity index ≥ 5) in 13 patients (65%). Thus, antirejection treatment was not administered to 8 of them; instead, the maintenance dose of immuno­suppressive therapy was increased or the immuno­suppressive protocol was converted to a regimen of tacrolimus plus mycophenolic acid. The remaining 5 patients received only pulse steroid treatment. Seven patients received intensive therapy that comprised intravenous immunoglobulin (1-2 g/weight/total) ± plasmapheresis (3-5 times) ± rituximab (375 mg/ weight/total) ± antithymocyte globulin. Of these patients, 3 (43%) had an immediate response to treatment, but 4 (57%) had progressive disease, 3 of whom experienced graft loss during the follow-up. Of the 12 patients whose GFR was < 30 mL/min/1.73 m2 at biopsy, 6 (50%) had progressive kidney failure, whereas of the 8 patients whose GFR was ≥ 30 mL/ min/1.73 m2 at biopsy, only 1 (12.5%) had progressive kidney failure (P = .06).

Outcome of patients with glomerulonephritis
Of the 6 patients with glomerulonephritis, 2 had IgA nephritis, 2 had membranoproliferative glomerulo­nephritis, 1 had membranous nephropathy, and 1 had pauci-immune crescentic glomerulonephritis. Total histologic score was high (chronicity index ≥ 5) in 5 patients (83.3%). The mean total histologic score (chronicity index) averaged 6.2 ± 2.6. One patient did not receive any specific treatment owing to diffuse chronic histologic changes. Five patients received pulse steroids, 1 patient received rituximab therapy, and 3 patients were treated with cyclophosphamide (1.5 mg/weight/day at 3-5 mo). One patient had an immediate, positive response to treatment; however, 3 patients (50%) with glomerulonephritis had progressive disease and 1 experienced graft loss during follow-up.

The mean serum creatinine levels of patients with glomerulonephritis were 2.5 ± 1.0 mg/dL (range, 1.6-4.5) at IB, 2.7 ± 1.7 mg/dL (range, 1.6-6.1) at discharge, 2.9 ± 1.7 mg/dL (range, 1.4-6.1) at month 6, and 2.9 ± 1.6 mg/dL (range, 1.4-6.1) at last follow-up (range, 16 ± 11 mo).

Of the 4 patients with idiopathic CAN, 1 had a progressive disease course and the other 3 had stable disease. None of them experienced graft loss during follow-up.

The mean follow-up after IB was 16 ±11 months (range, 6-41 mo). During this period, 11 patients (37%) had a progressive disease course and 7 patients (23%) resumed dialysis. The mean serum creatinine and proteinuria values for these patients at last follow-up were 2.9 ± 2.2 mg/dL and 2.3 ± 4.3 g/day. Of the 30 patients studied, those with a GFR of < 30 mL/min/1.72 m2 at IB (n = 15, 50%) were more likely to have a progressive disease course (53% vs 20%; P = .05) and more commonly needed to resume dialysis (40% vs 7%; P =.03). Compared with patients without CAN, patients with features of CAN seen on kidney biopsies presented with lower average GFR (38 ± 9.0 vs 52.7 ± 13.0 mL/min/1.72 m2; P = .03). Table 1 compares the demographic and laboratory data of patients with and without kidney disease progression after IB.

Discussion

In this study, the most frequently detected pathology in late-stage IBs of kidney transplant patients was acute graft rejection with a preponderance of significant chronic histologic changes. This finding was present in 20 of the cases (66.7%) in our series. Of the 7 patients who received intensive treatment for graft rejection, 4 (57%) experienced a progressive disease course and/or graft loss. In patients with chronic rejection, increasing maintenance immuno­suppressive drug dosages or switching to a low-dose, tacrolimus-based regimen decelerated disease progression.

Today, the most common cause of chronic allograft dysfunction is chronic antibody-mediated rejection. Several studies have found the incidence of chronic antibody-mediated rejection to be almost 25% in year 1 posttransplant and to reach 90% in year 10.2,4,8 Sellarés and colleagues evaluated allograft dysfunction in 315 consecutive patients in whom IBs were performed between 6 days and 32 years (median, 17 mo) after kidney transplant. They determined that rejection was responsible for 64% of all early and late graft dysfunction and that antibody-mediated rejection constituted 40% of all cases of allograft dysfunction, especially those occurring 5 years after transplant.4 Similarly, in our study, acute rejection was identified in 20 (67%) late-stage IBs, and of those, 16 (80%) showed complement component (C4d-mediated) acute rejection. In addition, chronic histologic changes were prominent in the majority of these cases. Moreover, a low GFR (< 30 mL/min/1.73 m2) at IB was an important determinant of progressive disease in this study. Clayton and associates recently analyzed the Australia and New Zealand Dialysis and Transplant Registry, which included 7949 patients. They reported a 2.2-fold increase in mortality and a 5.14-fold increase in death-censored graft failure in patients whose eGFR decreased ≥ 30% between years 1 and 3 after transplant.9 In our series, loss of GFR became evident after year 3 posttransplant and continued during and after IB in patients with a progressive disease course (Table 1). Therefore, along with histology, GFR changes in the preceding year can be a significant predictor of late graft dysfunction and aid in decision making.

Conclusions

As in the literature, in our study, glomerulonephritis was the second most common cause of graft dysfunction.6 The diagnosis of glomerulonephritis late after transplant was associated with chronic histologic changes in ≥ 80% of our patients, and disease progression persisted despite targeted treatment. There is an unmet need for novel biologic and immunologic markers for the early diagnosis and development of effective treatments in these cases.

In this study, rejection was the most common cause of graft dysfunction in the long term. Features of chronic histologic changes predominated in IBs taken ≥ 5 years after transplant. Regardless of the diagnosis, low GFR levels at biopsy were closely associated with poor renal outcomes.


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Volume : 15
Issue : 1
Pages : 265 - 268
DOI : 10.6002/ect.mesot2016.P132


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From the 1Department of Nephrology, the 2Department of General Surgery, and the 3Department of Pathology, Izmir Bozyaka Education and Research Hospital, Izmir, Turkey
Acknowledgements: The authors declare that they have no sources of funding for this study, and they have no conflicts of interest to declare.
Corresponding author: Erhan Tatar, Division of Nephrology, Izmir Bozyaka Education and Research Hospital, 35170, Karabaglar, Izmir, Turkey
Phone: +90 232 250 5050
E-mail: etatar@hotmail.com