Histopathological findings in transplanted kidneys

Color Doppler Guided in Early Renal Allograft Biopsy: A Safer and Non-Inferior Technique

BACKGROUND

This study compared a novel technique for renal allograft biopsy, color Doppler ultrasound-guided biopsy (CDUS-Bx), with routine ultrasound-guided biopsy (RUS-Bx).

METHODS

A retrospective review was conducted on 111 patients, with 42 undergoing CDUS-Bx and 69 undergoing RUS-Bx. Urologists used an 18-gauge automatic spring-loaded biopsy needle for all procedures. CDUS-Bx tissue collection was guided by identifying renal vessels with color Doppler mode.

RESULTS

Overall, the adequacy rate was 90.1%, with a higher number of glomeruli obtained in the CDUS-Bx group (25.6 ± 10.3 vs. 20.6 ± 11.3, P = .008). Acute tubular necrosis was the most frequent pathological diagnosis, with a higher prevalence in the CDUS-Bx group (69% vs 40.6%). T cell-mediated rejection had a lower incidence in the CDUS-Bx group (4.8% vs 21.7%), and antibody-mediated rejection was comparable between the 2 groups. The most common complication was microscopic hematuria, which was significantly less frequent in the CDUS-Bx group (48.7% vs 70.1%, P = .028), but there was no significant difference in the rate of gross hematuria between CDUS-Bx and RUS-Bx (11.9% vs 11.6%, P = .961). The number of cores was the only predictor of adequate biopsy, with a 93.2% adequacy rate after 3 cores of allograft biopsy. Multivariate analysis revealed that only the guiding type, CDUS-Bx, was associated with less microscopic hematuria (adjusted odds ratio 0.325, P = .018).

CONCLUSIONS

Color Doppler ultrasound-guided biopsy had comparable tissue adequacy to RUS-Bx, with a lower incidence of microscopic hematuria. These findings suggest that CDUS-Bx may be a safe and effective alternative to RUS-Bx for allograft biopsy.

Clinical and Pathological Significance of Mesangial C1q Deposition in Kidney Transplant Recipients with Recurrent IgA Nephropathy and Patients with Native IgA Nephropathy

INTRODUCTION

In kidney transplant recipients (KTRs) whose primary disease is IgA nephropathy (IgAN), IgAN recurrence occurs in approximately half of patients by 5 years postoperatively and is associated with graft survival. Although the alternative and lectin pathways are important in the primary pathogenesis of IgAN, the significance of mesangial C1q deposition, which triggers the classical pathway, is unknown. We investigated the clinicopathological significance of mesangial C1q deposition in both recurrent IgAN in KTRs and native IgAN.

METHODS

Between 2000 and 2021, we conducted a 1:2 matched case-control study of 18 KTRs diagnosed with recurrent IgAN, with a group of native IgAN patients as the control. We evaluated the rate and presence/absence of mesangial C1q deposition in terms of pathological findings and kidney outcomes in each group.

RESULTS

The rate of mesangial C1q deposition was significantly higher in the recurrent IgAN patients in KTRs than in native IgAN patients (11/18 [61.1%] vs. 5/36 [13.9%], p = 0.001). In the former group, the incidence of glomerular crescents was relatively higher in C1q-positive patients. There was no significant difference in the annual rate of estimated glomerular filtration rate decline between C1q-positive and C1q-negative patients in either group.

CONCLUSION

Mesangial C1q deposition was more frequent in KTRs with recurrent IgAN than in patients with native IgAN, but we found no difference in kidney outcomes with respect to mesangial C1q deposition. Further large-scale investigations of the importance of mesangial C1q deposition are needed in both KTRs with recurrent IgAN and patients with native IgAN.

Current Status and Perspectives on Recurrent IgA Nephropathy after Kidney Transplantation

IgA nephropathy (IgAN) is the most common form of glomerulonephritis worldwide. IgAN progresses to end-stage kidney disease in 20-40% of patients within 20 years of diagnosis. Kidney transplantation is the most effective option for patients with end-stage kidney disease caused by IgAN, but recurrence can occur in the transplanted kidney. The IgAN recurrence rate varies from 1% to 10% per year and varies according to the follow-up period, diagnostic modality, and biopsy criteria. Of note, studies based on protocol biopsies have reported a higher incidence of recurrence, which also occurred earlier after transplantation. In addition, recent data show that recurrence of IgAN is a more significant cause of allograft failure than previously believed. Little is known about the pathophysiology of IgAN recurrence, but several potential biomarkers have been investigated. Among them, galactose-deficient IgA1 (Gd-IgA1), IgG anti-Gd-IgA1 antibodies, and soluble CD89 could play a pivotal role in disease activity. This review aims to describe the current status of recurrent IgAN, including the incidence, clinical characteristics, risk factors, and future perspectives, with a focus on the available therapeutic approaches.

Challenges Posed by the Banff Classification: Diagnosis and Treatment of Chronic Active T-Cell-Mediated Rejection

The three primary sites of acute T-cell-mediated rejection (TCMR) in transplanted kidneys are the tubular epithelial cells, interstitium, and the vascular endothelial cells. The pathology of acute lesions is characterized by inflammatory cell infiltration; the final diagnosis suggested by the Banff 2019 classification is guided by grading of tubulitis (the t score), interstitial inflammation (the i score), and endarteritis (the v score). Consistent major issues when using the Banff classification are the etiological classifications of interstitial fibrosis and tubular atrophy (IFTA). From 2015 to 2019, technological advances (i.e., genetic analysis in paraffin sections) increased our understanding of IFTA status in patients with smoldering acute TCMR and the roles played by inflammatory cell infiltration (the i-IFTA score) and tubulitis (the t-IFTA score) in IFTA. These two scores were introduced when establishing the diagnostic criteria for chronic active TCMR. Despite the increase in complexity and the lack of a consensus treatment for chronic active TCMR, the Banff classification may evolve as new techniques (i.e., genetic analysis in paraffin sections and deep learning of renal pathology) are introduced. The Banff conference proceeded as follows. First, lesions were defined. Next, working groups were established to better understand the lesions and to derive better classification methods. Finally, the new Banff classification was developed. This approach will continue to evolve; the Banff classification will become a very useful diagnostic standard. This paper overviews the history of TCMR diagnosis using the Banff classification, and the clinical importance, treatment, and prospects for acute and chronic active TCMR.

Outcomes of paediatric kidney transplant recipients using the updated 2013/2017 Banff histopathological classification for antibody-mediated rejection

BACKGROUND

After the major changes with regard to acute and chronic ABMR in the Banff classification initiated in 2013, there has been an improvement in diagnosing antibody-mediated rejection (ABMR) in adult studies but no data have been published in the paediatric population.

METHODS

We assessed 56 paediatric kidney transplant biopsies due to kidney dysfunction in patients with donor-specific antibodies (DSA) in a retrospective single-centre study between January 2006 and March 2012. The results were compared with 2003/2007 Banff classification noting the subsequent 2017 and 2019 modifications do not change the 2013 Banff classification with regard to acute antibody-mediated rejection (apart from the addition of gene transcripts/classifiers that do not affect our analysis).

RESULTS

Following the 2013 Banff classification, there were seven cases (12.5%) diagnosed with ABMR that would have been misclassified when applying the 2003/2007 classification. Evaluating the histological features of all ABMR-related cases, we report the importance of v- (intimal arteritis) and t- (tubulitis) lesions: absence of v- and t- lesions in the biopsy is related to significantly higher kidney allograft survival (OR 7.3, 95%CI 1.1-48.8, p = 0.03 and OR 5.3, 95%CI 1.2-25.5, p = 0.04 respectively). Moreover, absence of t- lesions was associated with significantly fewer rejection episodes the year after the initial biopsy (OR 5.1, 95%CI 1.4-19.8, p = 0.01).

CONCLUSIONS

Our study supports that the updated 2013 Banff classification shows superior clinicopathological correlation in identifying ABMR in paediatric kidney transplant recipients. Our results can be extrapolated to the recently updated 2019 Banff classification.

Histopathological features of kidney and renal prognosis in patients with preeclampsia

OBJECTIVE

Understanding the long-term prognosis of preeclampsia (PE) is important. Proteinuria and poor renal function persist in some PE patients, but the relationship between their histopathological findings of kidney and renal prognosis is unknown. Our objective was to clarify the relationship between clinicopathological features and renal prognosis in PE patients.

STUDY DESIGN

Retrospective observational study.

MAIN OUTCOME MEASURES

Seventy patients who had been referred to the Niigata University Hospital between 1977 and 2014 and were diagnosed with PE were classified into unimproved and improved groups. The unimproved group included patients whose serum creatinine level had doubled and/or whose proteinuria had persisted until the end of observation, which included three patients with end-stage kidney disease (ESKD). The improved group included patients whose serum creatinine level did not double and whose proteinuria had disappeared until the last observation. We examined and compared these patients' characteristics, clinical and laboratory findings, and renal histopathological findings from percutaneous kidney biopsies.

RESULTS

There were no significant differences in the clinical backgrounds and clinical findings between the two groups during pregnancy. However, light microscopy findings of their kidney biopsies were able to identify significantly more severe duplications of the capillary loop, interstitial cell infiltration, and interstitial fibrosis in the unimproved group.

CONCLUSIONS

Histopathological examination of the kidney may be a valid method for predicting the long-term prognosis of renal function and for histological a risk assessment of poor renal recovery in PE patients.

Evaluation of Early Renal Allograft Dysfunction from Living Donors among Egyptian Patients (Histopathological and Immunohistochemical Study)

BACKGROUND: Early renal graft dysfunction is a major problem in the early post-transplantation period and is considered a major cause of graft loss. Clinical diagnosis based on the clinical criteria alone is unreliable; therefore, biopsy remains the gold standard to differentiate between rejection and non-rejection causes. AIM: This study was designed to identify and differentiate between causes of early graft dysfunction during the first post-transplantation month and to correlate between histological lesions and immunohistochemistry (IHC) for accurate diagnosis and a better outcome. MATERIALS AND METHODS: A total of 163 renal allograft biopsies, performed in the first post-transplantation month over 6 years, were included in the study. New sections were prepared from the paraffin blocks and stained with conventional stains. Additional sections were prepared and treated by complement fragment 4d (C4d) and cluster differentiation 3 (CD3) antibodies for IHC evaluation. RESULTS: All the studied cases were from living donors. The mean patient age was 39 years with predominant males. The clinical indication for most biopsies (94.5%) was impaired graft function. Acute rejection (AR) was the main diagnostic category observed in (98/163, 60.1%); out of which, T cell-mediated rejection (TCMR) was observed in (62/98, 63.2%). Drug toxicity was suspected in (53/163, 32.5%), acute tubular injury (ATI) not otherwise specified (nos) in (21/163, 12.9%), and other lesions including thrombotic microangiopathy were observed in the remaining biopsies. The most common cause of graft dysfunction in the 1st and 2nd weeks was AR representing. A significant correlation was seen between mild glomerulitis (g1) and mild peritubular capillaritis (PTC) 1, on the one side, and negative C4d staining, on the other side. No significant correlation was seen between moderate glomerulitis (g2) and moderate ptc2 at one side and positive C4d staining at the other side reflecting the poor association between the microvascular inflammation (“g” and “ptc” scores) and C4d positivity (r = 0.2). Missed mild tubulitis (t1) was found in a single case and missed moderate tubulitis (t2) was found in a single case detected by CD3 IHC. CONCLUSION: AR and drug toxicity account for the majority of early graft dysfunction, however, other pathological lesions, per se or coincide with them may be the cause. The significance of g2 per se as a marker for diagnosis of antibody-mediated rejection requires further study. Considering C4d score 1 (by IHC) positive; also requires further study with follow-up.

A Role for Human Renal Tubular Epithelial Cells in Direct Allo-Recognition by CD4+ T-Cells and the Effect of Ischemia-Reperfusion

Direct allorecognition is the earliest and most potent immune response against a kidney allograft. Currently, it is thought that passenger donor professional antigen-presenting cells (APCs) are responsible. Further, many studies support that graft ischemia-reperfusion injury increases the probability of acute rejection. We evaluated the possible role of primary human proximal renal tubular epithelial cells (RPTECs) in direct allorecognition by CD4+ T-cells and the effect of anoxia-reoxygenation. In cell culture, we detected that RPTECs express all the required molecules for CD4+ T-cell activation (HLA-DR, CD80, and ICAM-1). Anoxia-reoxygenation decreased HLA-DR and CD80 but increased ICAM-1. Following this, RPTECs were co-cultured with alloreactive CD4+ T-cells. In T-cells, zeta chain phosphorylation and c-Myc increased, indicating activation of T-cell receptor and co-stimulation signal transduction pathways, respectively. T-cell proliferation assessed with bromodeoxyuridine assay and with the marker Ki-67 increased. Previous culture of RPTECs under anoxia raised all the above parameters in T-cells. FOXP3 remained unaffected in all cases, signifying that proliferating T-cells were not differentiated towards a regulatory phenotype. Our results support that direct allorecognition may be mediated by RPTECs even in the absence of donor-derived professional APCs. Also, ischemia-reperfusion injury of the graft may enhance the above capacity of RPTECs, increasing the possibility of acute rejection.

Molecular Analysis of Renal Allograft Biopsies: Where Do We Stand and Where Are We Going?

A renal core biopsy for histological evaluation is the gold standard for diagnosing renal transplant pathology. However, renal biopsy interpretation is subjective and can render insufficient precision, making it difficult to apply a targeted therapeutic regimen for the individual patient. This warrants a need for additional methods assessing disease state in the renal transplant. Significant research activity has been focused on the role of molecular analysis in the diagnosis of renal allograft rejection. The identification of specific molecular expression patterns in allograft biopsies related to different types of allograft injury could provide valuable information about the processes underlying renal transplant dysfunction and can be used for the development of molecular classifier scores, which could improve our diagnostic and prognostic ability and could guide treatment. Molecular profiling has the potential to be more precise and objective than histological evaluation and may identify injury even before it becomes visible on histology, making it possible to start treatment at the earliest time possible. Combining conventional diagnostics (histology, serology, and clinical data) and molecular evaluation will most likely offer the best diagnostic approach. We believe that the use of state-of-the-art molecular analysis will have a significant impact in diagnostics after renal transplantation. In this review, we elaborate on the molecular phenotype of both acute and chronic T cell-mediated rejection and antibody-mediated rejection and discuss the additive value of molecular profiling in the setting of diagnosing renal allograft rejection and how this will improve transplant patient care.

Renal Transplant Pathology: Demographic Features and Histopathological Analysis of the Causes of Graft Dysfunction

Background

Renal transplant has emerged as a preferred treatment modality in cases of end-stage renal disease; however, a small percentage of cases suffer from graft dysfunction.

Aim

To evaluate the renal transplant biopsies and analyze the various causes of graft dysfunction.

Materials and Methods

163 renal transplant biopsies, reported between 2014 and 2019 and who fulfilled the inclusion criteria, were evaluated with respect to demographics, clinical, histological, and immunohistochemical features.

Results

Of 163 patients, 26 (16%) were females and 137 (84%) were males with a mean age of 34 ± 7 years. 53 (32.5%) cases were of rejection (ABMR and TCMR), 1 (0.6%) was borderline, 15 were of IFTA, and rest of 94 cases (57.7%) belonged to the others category. SCr (serum creatinine) in cases of rejection was 3.85 ± 0.55 mg/dl. Causes of early graft dysfunction included active ABMR (7.1 ± 4.7 months), acute TCMR (5.5 months), and acute tubular necrosis (after 6 ± 2.2 months of transplant) while the causes of late rejection were CNIT and IFTA (34 ± 4.7 and 35 ± 7.8 months, respectively).

Conclusion

Renal graft dysfunction still remains a concerning area for both clinicians and patients. Biopsy remains the gold standard for diagnosing the exact cause of graft dysfunction and in planning further management.

High levels of dd-cfDNA identify patients with TCMR 1A and borderline allograft rejection at elevated risk of graft injury

The clinical importance of subclinical, early T cell-mediated rejection (Banff TCMR 1A and borderline lesions) remains unclear, due, in part to the fact that histologic lesions used to characterize early TCMR can be nonspecific. Donor-derived cell-free DNA (dd-cfDNA) is an important molecular marker of active graft injury. Over a study period from June 2017 to May 2019, we assessed clinical outcomes in 79 patients diagnosed with TCMR 1A/borderline rejection across 11 US centers with a simultaneous measurement of dd-cfDNA. Forty-two patients had elevated dd-cfDNA (≥0.5%) and 37 patients had low levels (<0.5%). Elevated levels of dd-cfDNA predicted adverse clinical outcomes: among patients with elevated cfDNA, estimated glomerular filtration rate declined by 8.5% (interquartile rate [IQR] -16.22% to -1.39%) (-3.50 mL/min/1.73 m2 IQR -8.00 to -1.00) vs 0% (-4.92%, 4.76%) in low dd-cfDNA patients (P = .004), de novo donor-specific antibody formation was seen in 40% (17/42) vs 2.7% (P < .0001), and future or persistent rejection occurred in 9 of 42 patients (21.4%) vs 0% (P = .003). The use of dd-cfDNA may complement the Banff classification and to risk stratify patients with borderline/TCMR 1A identified on biopsy.

Impact of primary diabetic nephropathy on arteriolar hyalinosis lesions in patients following kidney transplantation

AIM

Arteriolar hyalinosis (AH) is a common lesion in allograft biopsies taken following kidney transplantation. Recent studies have shown that severe AH may predict transplant outcomes and provide information about previous exposure to certain drugs, such as calcineurin inhibitors (CNI). However, the incidence of AH as a direct result of diabetic nephropathy (DN) after kidney transplantation has not been fully evaluated. This study aimed to assess the impact of primary DN on the development of AH lesions in patients who underwent kidney transplantation.

METHODS

Eighty-three patients who underwent living-donor kidney transplantation between April 2005 and June 2015 were enrolled in this study. A total of 33 patients had DN prior to transplantation. Allograft biopsies were scored according to the Banff classification, and the relationship between the individual histological lesions and clinical baseline data was assessed.

RESULTS

At early biopsy (3-12 months), there were no differences in the rates of AH lesions between the DN group and the non-DN group (ah ≥ 1: 37% vs. 41.3%, P = 0.719; aah ≥ 1: 14.8% vs. 6.5%; P = 0.453). However, there were significant differences between the groups in biopsies taken more than 3 years after the transplant (ah ≥ 2: 83.3% vs. 36.8%, P = 0.013; aah ≥ 2: 66.7% vs. 21.1%, P = 0.011). Multivariable analysis showed that both the length of time after transplantation and the presence of DN were independent risk factors for ah ≥ 2 (odds ratio [OR]: 2.55, 95% confidence interval [CI]: 1.47-19.54, P = 0.011) and aah ≥ 2 (OR: 7.55, 95% CI: 1.49-38.33, P = 0.015).

CONCLUSION

This is the first report showing that the presence of primary DN disease contributes to the development of severe AH late in the course after kidney allografts.

Cell mediated rejection revisited: Past, current, and future directions

The Banff histopathology classification system is the gold standard for assessing the causes of kidney allograft dysfunction triggered by antibody-mediated and T-cell-mediated immune reactions, thereby providing mechanistic insight and guiding therapeutic decisions. The original Banff classification (1993) consisted of four histological categories representing cell-mediated rejection: interstitial inflammation (i), tubulitis (t), endoarteritis (v), and transplant glomerulitis (g). The revised Banff 2007 classification added total inflammation score (ti) from both scarred and unscarred areas based on evolving interpretations of interstitial infiltrates. Further reappraisal of cell-mediated interstitial inflammation led to the introduction of a new inflammation score specific for areas of interstitial fibrosis and tubular atrophy, termed i-IF/TA, in the Banff 2015 scheme, establishment of a new Banff working group on T-cell-mediated rejection (TCMR), and revised criteria of chronic active TCMR in Banff 2017 classification. These Banff scheme updates reflect the general recognition that chronic interstitial inflammation is a common denominator of poor kidney allograft outcome. However, revised theories on the pathogenic importance of interstitial infiltrates have created difficulties in interpretation of chronic tubulointerstitial inflammation, as there are currently no histological criteria to discriminate immune-mediated tissue injury from 'non-specific' injury. Evolving theories on vascular lesions, both active and chronic, have also complicated histological assessment by obscuring the distinction between antibody-mediated and T-cell-mediated tissue injury. This review provides an overview of recent ideas on interstitial inflammation and vascular lesions based on emerging concepts of T-cell-mediated rejection.