Actual practices in nephropathology: a survey and comparison with best practices

Two-Week Protocol Biopsy in Renal Allograft: Feasibility, Safety, and Outcomes

Background: Protocol biopsy in renal allograft helps to early detect subclinical rejection (SCR) in patients who have no abnormal clinical and laboratory findings. Still, there are rare reports about the techniques and outcomes of two-week protocol biopsy. The aim of this study was to assess two-week protocol biopsy regarding the technical feasibility, procedure safety, and clinical outcomes. Methods: A total of 894 protocol biopsies were performed in adult recipients between 2012 and 2019. Two-week and one-year protocol biopsies were guided with ultrasound in 842 and 399 patients by one of four radiologists with wide range of biopsy experience, respectively. These protocol biopsies were compared in terms of feasibility and safety. Standard references were clinico-laboratory findings and biopsy examinations. Results: The median period of two-week and one-year protocol biopsies were 12 days (10–20 days) and 383 days (302–420 days), respectively. All protocol biopsies were technically successful and there was no difference between radiologists regarding technical success and complications (p = 0.453). Major complication (Clavien–Dindo grading II–IV) rates of two-week and one-year protocol biopsies were 0.3% (3/842) and 0.2% (1/399), respectively (p = 1.000). However, univariate analysis demonstrated that platelet count < 100 K/mL and blood urea nitrogen ≥ 40 mg/dL were associated with major complications in two-week protocol biopsy. The SCRs of these protocol biopsies were 15.4% (130/842) and 33.6% (134/399), respectively (p < 0.001). Conclusion: Two-week protocol biopsy is technically feasible and safe. It contributes to early detecting a substantial number of SCRs. Prior to the biopsy, platelet count and blood urea nitrogen should be carefully checked to predict major complications.

Low-vacuum scanning electron microscopy may allow early diagnosis of human renal transplant antibody-mediated rejection

Antibody-mediated rejection (ABMR) is an important cause of both short- and long-term injury to renal allografts. Transplant glomerulopathy (TG) is strongly associated with ABMR and reduced graft survival. Ultrastructural changes in early-stage ABMR include TG as a duplication of the glomerular basement membrane (GBM), which can be observed only by transmission electron microscopy (TEM). Low-vacuum scanning electron microscopy (LVSEM) is a new technique that allows comparatively inexpensive, rapid, and convenient observations with high magnification. We analyzed human renal transplants using LVSEM and evaluated the ultrastructural changes representing TG in ABMR. GBM duplication was more clearly visible in the LVSEM images than in the light microscopy (LM) images. In the ABMR group, the cg score of the Banff classification was higher in 54% (7/13) of specimens for LVSEM images than for LM images. And 4 specimens exhibited duplication of the GBM analyzed by LVSEM, but not by LM. In addition, three-dimensional ultrastructural changes, such as coarse meshwork structures of GBM, were observed in ABMR specimens. The ABMR group also exhibited ultrastructural changes in the peritubular capillary basement membranes. In conclusion, analyses of renal transplant tissues using LVSEM allows the identification of GBM duplication and ultrastructural changes of basement membranes at the electron microscopic level, and is useful for early-stage diagnosis of ABMR.

Characteristics of patients with coexisting DNAJB9-associated fibrillary glomerulonephritis and IgA nephropathy

Background

Coexistence of fibrillary glomerulonephritis (FGN) and immunoglobulin A (IgA) nephropathy (IgAN) in the same kidney biopsy (FGN–IgAN) is rare, and the clinicopathologic characteristics and outcome of this dual glomerulopathy are unknown.

Methods

In this study, 20 patients with FGN–IgAN were studied and their characteristics were compared with 40 FGN and 40 IgAN control patients.

Results

Concurrent IgAN was present in 1.8% of 847 consecutive FGN cases and was the second most common concurrent glomerulopathy after diabetic nephropathy. FGN–IgAN patients were overwhelmingly White (94%) and contrary to FGN patients were predominantly (60%) males. Compared with IgAN patients, FGN–IgAN patients were older, had higher proteinuria, a higher incidence of renal insufficiency, and a lower incidence of microhematuria and gross hematuria at diagnosis. Six (30%) patients had malignancy, autoimmune disease or hepatitis C infection, but none had a secondary cause of IgAN or clinical features of Henoch–Schonlein purpura. Histologically, all cases exhibited smudgy glomerular staining for immunoglobulin G and DnaJ homolog subfamily B member 9 (DNAJB9) with corresponding fibrillary deposits and granular mesangial staining for IgA with corresponding mesangial granular electron-dense deposits. On follow-up (median 27 months), 10 of 18 (56%) FGN–IgAN patients progressed to end-stage kidney disease (ESKD), including 5 who subsequently died. Serum creatinine at diagnosis was a poor predictor of renal survival. The proportion of patients reaching ESKD or died was higher in FGN–IgAN than in IgAN. The median Kaplan–Meier ESKD-free survival time was 44 months for FGN–IgAN, which was shorter than IgAN (unable to compute, P = 0.013) and FGN (107 months, P = 0.048).

Conclusions

FGN–IgAN is very rare, with clinical presentation and demographics closer to FGN than IgAN. Prognosis is guarded with a median renal survival of 3.6 years. The diagnosis of this dual glomerulopathy requires careful evaluation of immunofluorescence findings, and electron microscopy or DNAJB9 immunohistochemistry.

A retrospective analysis of complication and adequacy rates of ultrasound-guided native and transplant non-focal renal biopsies

PURPOSE

To assess non-focal ultrasound (US)-guided renal biopsy complication and adequacy rates at our institution.

METHODS

A retrospective analysis of 1067 non-focal renal biopsy cases between 2012 and 2015. Information collected including type of US-guided procedure (US-localized by nephrology vs. real-time US-guided by radiology), sample adequacy, complications, blood work, and histologic data.

RESULTS

602 biopsies were performed by radiology (56.4%) and 465 (43.6%) by nephrology. The overall adequacy rate was 96.1%, with an US-localized rate of 95.7% and real-time US-guided rate of 96.3% (p = 0.58). A lower adequacy rate was noted for 1 biopsy core but there were no differences between 2 and 6 cores (p = 0.001). A lower adequacy rate was found for transplant biopsies vs. native biopsies (p = 0.03). Complication rates were as follows-minor 5.9%, major 4.3%, and life-threatening 0.8%. There were no differences in complication rates between the US-localized and real-time US-guided techniques (p = 0.63). Complications were more likely in patients with a lower hemoglobin, higher serum creatinine, and lower albumin (p < 0.05). No differences were found between the number of cores performed and the complication rates. The complication rate was similar between transplant biopsies vs. native biopsies (p = 0.2). The adequacy rate was lower in trainees (p = 0.01) than experienced radiologists.

CONCLUSIONS

No significant differences were found between US-localized vs. real-time US-guided techniques. A lower adequacy rate was found for trainee radiologists and for transplant biopsies. A lower adequacy rate was also observed when only 1 biopsy pass was performed.

Paraffin Immunofluorescence: A Valuable Ancillary Technique in Renal Pathology

Immunofluorescence on frozen tissue is the gold standard immunohistochemical technique for evaluation of immune deposits in the kidney. When frozen tissue is not available or lacks glomeruli, immunofluorescence can be performed on paraffin tissue after antigen retrieval (paraffin immunofluorescence). Excellent results can be obtained by paraffin immunofluorescence in most immune complex-mediated glomerulonephritides and dysproteinemia-associated kidney lesions, and thus this technique has become a valuable salvage technique in renal pathology. Furthermore, new data have emerged suggesting that paraffin immunofluorescence can be used as an unmasking technique, as it is more sensitive than frozen tissue immunofluorescence in some kidney lesions, such as crystalline light chain proximal tubulopathy and is needed to establish the diagnosis of certain unique lesions, such as membranous-like glomerulopathy with masked IgG kappa deposits and membranoproliferative glomerulonephritis with masked monotypic Ig deposits. However, it is important to recognize and be aware of the limitations and pitfalls associated with paraffin immunofluorescence. These include poor sensitivity for detection of C3 deposits and for the diagnosis of primary membranous nephropathy. Here, we summarize the available techniques of paraffin immunofluorescence, review its role and performance as a salvage and unmasking technique in renal pathology, address its limitations and pitfalls, and highlight unusual forms of glomerulopathy that require paraffin immunofluorescence for diagnosis.

DNAJB9 Is a Specific Immunohistochemical Marker for Fibrillary Glomerulonephritis

INTRODUCTION

Fibrillary glomerulonephritis (FGN) is a rare disease with unknown pathogenesis and a poor prognosis. Until now, the diagnosis of this disease has required demonstration of glomerular deposition of randomly oriented fibrils by electron microscopy that are Congo red negative and stain with antisera to Igs. We recently discovered a novel proteomic tissue biomarker for FGN, namely, DNAJB9.

METHODS

In this work, we developed DNAJB9 immunohistochemistry and tested its sensitivity and specificity for the diagnosis of FGN. This testing was performed on renal biopsy samples from patients with FGN (n = 84), amyloidosis (n = 21), a wide variety of non-FGN glomerular diseases (n = 98), and healthy subjects (n = 11). We also performed immunoelectron microscopy to determine whether DNAJB9 is localized to FGN fibrils.

RESULTS

Strong, homogeneous, smudgy DNAJB9 staining of glomerular deposits was seen in all but 2 cases of FGN. The 2 cases that did not stain for DNAJB9 were unique, as they had glomerular staining for IgG only (without κ or λ) on immunofluorescence. DNAJB9 staining was not observed in cases of amyloidosis, in healthy subjects, or in non-FGN glomerular diseases (with the exception of very focal staining in 1 case of smoking-related glomerulopathy), indicating 98% sensitivity and > 99% specificity. Immunoelectron microscopy showed localization of DNAJB9 to FGN fibrils but not to amyloid fibrils or immunotactoid glomerulopathy microtubules.

CONCLUSION

DNAJB9 immunohistochemistry is sensitive and specific for FGN. Incorporation of this novel immunohistochemical biomarker into clinical practice will now allow more rapid and accurate diagnosis of this disease.

Refinement of the criteria for ultrastructural peritubular capillary basement membrane multilayering in the diagnosis of chronic active/acute antibody-mediated rejection

Chronic active/acute antibody-mediated rejection (cABMR) is the main cause of late renal allograft loss. Severe peritubular capillary basement membrane multilayering (PTCML) assessed on electron microscopy is one diagnostic feature of cABMR according to the Banff 2013 classification. We aimed to refine the PTCML criteria for an earlier diagnosis of cABMR. We retrospectively investigated ultrastructural features of 159 consecutive renal allografts and 44 nonallografts. The presence of serum donor-specific antibodies at the time of biopsy of allografts was also examined. Forty-three patients (27.0%) fulfilled the criteria of cABMR, regardless of PTCML, and comprised the cABMR group. Forty-one patients (25.8%) did not exhibit cABMR features and comprised the non-cABMR allograft control group. In addition, 15 zero-day wedge resections and 29 native kidney biopsies comprised the nonallograft control group. When the diagnostic accuracies of various PTCML features were assessed using the cABMR and non-cABMR allograft control groups, ≥4 PTCML, either circumferential or partial, in ≥2 peritubular capillaries of the three most affected capillaries exhibited the highest AUC value (0.885), greater than the Banff 2013 classification (0.640). None of the nonallograft control groups exhibited PTCML features. We suggest that ≥4 PTCML in ≥2 peritubular capillaries of the three most affected cortical capillaries represents the proper cutoff for cABMR.

Lack of electron microscopy hinders correct renal biopsy diagnosis: A study from India

Electron microscopy (EM) is performed routinely on all native kidney biopsies in the western world. However, in India, it is not regularly performed due to non-availability and financial constraints. The aim of this prospective study was to evaluate the usefulness of routinely performing EM on native kidney biopsies. In order to eliminate selection bias, all consecutive native kidney biopsies were included in this study, provided they had adequate tissue for light, immunofluorescence (IF), and EM. The biopsies were reported on the basis of light and IF microscopy. EM was performed on each case by another pathologist who also independently reviewed the light microscopic slides and IF images. The findings were then reviewed to assess how the ultrastructural features contributed to the primary diagnosis and assigned to one of the following categories: 1. Crucial for diagnosis, 2. Important contribution, or 3. Not required. Of the 115 cases evaluated, EM was crucial in 12% of the cases. In 20% of the cases, it provided important confirmatory information and in the remaining 68% cases, EM was not considered required. This study supports the use of EM as a routine diagnostic tool in the evaluation of native kidney biopsies. There is an urgent need for availability and accessibility of EM in our country.

Factors Contributing to the Success of Ultrasound-Guided Native Renal Biopsy

OBJECTIVES

The purpose of this study was to evaluate factors contributing to the success of ultrasound-guided native renal biopsy.

METHODS

We retrospectively identified patients who had ultrasound-guided native renal biopsy at our institution over a 10-year period. We reviewed the imaging and electronic medical records to collect demographic information and clinical data, including pathologic results. Biopsy samples were categorized and compared on the basis of the number of glomeruli (optimal [≥20] versus suboptimal [<20]) and the pathologist's reported diagnostic confidence (high confidence versus limited confidence). Procedure details, including the operator and the use of the cortical tangential approach, were also obtained.

RESULTS

For 282 patients with biopsies using 18-gauge needles, the number of passes made was significantly higher for optimal (P < .001) and high-confidence (P < .001) specimens than for suboptimal and limited-confidence specimens. The cortical tangential approach was used more frequently for optimal (P< .001) and high-confidence (P = .01) specimens than for suboptimal and limited-confidence specimens. Radiologists routinely doing ultrasound-guided procedures of all types had significantly more optimal (P= .01) and high-confidence (P= .001) specimens than radiologists with limited ultrasound experience. The distance to the kidney, cortical thickness, glomerular filtration rate, and body mass index were not significant factors.

CONCLUSIONS

The ultrasound-guided procedural experience of the operator, taking more than 1 specimen, and the use of the cortical tangential approach significantly improved the pathologic material obtained during native renal biopsies.

Paraffin immunofluorescence in the renal pathology laboratory: more than a salvage technique

Immunofluorescence studies on paraffin-embedded tissue after Pronase digestion (paraffin immunofluorescence) is used as a salvage technique in renal pathology, when frozen tissue for routine immunofluorescence is inadequate. We have recently found that it is also useful in rare cases in which the immune deposits are 'masked' on routine immunofluorescence, giving false-negative staining by routine immunofluorescence and positive staining by paraffin immunofluorescence. This study aims to evaluate the role of paraffin immunofluorescence in clinical practice with emphasis on its utility to avoid misdiagnosis of cases with masked immune complex deposits. Paraffin immunofluorescence was used in 304 (6.1%) of 4969 native biopsies reviewed from our files. In 207 (68.1%) cases, paraffin immunofluorescence was used as a salvage technique. It was necessary for diagnosis in 24 (11.6%) and had a significant contribution in 63 (30.4%) of these cases. Paraffin immunofluorescence was used to evaluate masked deposits in 97 (31.9%) cases. In 61 (62.9%) of these cases it was used to evaluate masked immune complex glomerular deposits, and in 36 cases (37.1%) it was used to evaluate masked paraproteins. Of the cases where immune complex deposits were sought, paraffin immunofluorescence was necessary for diagnosis in 16 (26.2%) cases and had a significant contribution in 4 (6.6%) cases. Fourteen of the 20 cases with masked deposits had C3 dominant stain by routine immunofluorescence, which could have been misdiagnosed as C3 glomerulopathy. Overall, paraffin immunofluorescence was necessary or had a significant contribution to diagnosis in >1/3 of the cases and is a valuable technique in renal pathology.

Membranous-like glomerulopathy with masked IgG kappa deposits

The diagnostic classification of glomerulonephritis is determined by the interplay of changes seen using light, immunofluorescence, and electron microscopy of the renal biopsy. Routine direct immunofluorescence on fresh tissue is currently considered the gold standard for the detection and characterization of immune deposits. We recently found a peculiar form of glomerular immune complex deposition in which masked deposits required an antigen-retrieval step to be visualized. Over a 2-year period, 14 cases were characterized by numerous, large subepithelial deposits visualized by electron microscopy and C3-predominant staining by routine immunofluorescence on fresh tissue with weak to negative immunoglobulin staining. Repeat immunofluorescence after digestion of the formalin-fixed paraffin-embedded tissue with pronase elicited strong IgG-κ staining restricted within the deposits. The patients were often young with a mean age of 26 years and commonly had clinical evidence of vague autoimmune phenomenon. The clinicopathologic findings in this unusual form of glomerulopathy do not fit neatly into any currently existing diagnostic category. We have termed this unique form of glomerulopathy membranous-like glomerulopathy with masked IgG-κ deposits.

The renal biopsy in the genomic era

Renal biopsy was introduced in the 1950s. By 1980 the pathologic diagnostic criteria for the majority of medical kidney diseases known today, including pediatric diseases, were established using light, electron microscopy and immunohistochemistry. However, it has become clear that there are limitations in the morphologic evaluation, mainly because a given pattern of injury can be caused by different aetiologies and, conversely, a single aetiology may present with more than one histological pattern. An explosion in kidney disease research in the last 20-30 years has brought new knowledge from bench to bedside rapidly and resulted in new molecular and genetic tools that enhance the diagnostic and prognostic power of the renal biopsy. Genomic technologies such as polymerase chain reaction (PCR), in situ hybridization and oligonucleotide microarrays, collectively known as genomics, detect single or multiple genes underscoring the pathologic changes and revealing specific causes of injury that may require different treatment. The aims of this review are to (1) summarize current recommendations for diagnostic renal biopsies encompassing light microscopy, immunofluorescence or immunohistochemistry and electron microscopy; (2) address the limitations of morphology; (3) show current contributions of genomic technologies adjunct to the renal biopsy, and provide examples of how these may transform pathologic interpretation into molecular disease phenotypes.

Sometimes when you hear hoof beats, it could be a zebra: consider the diagnosis of Fabry disease

BACKGROUND

Fabry disease is an X-linked lysosomal storage disorder that results from a deficiency of the enzyme α-galactosidase A. Fabry disease is present in 4-5% of men with unexplained left ventricular hypertrophy or cryptogenic stroke. As enzyme replacement therapy is now more widely available, it is important to recognise the signs and symptoms of the disease and establish the diagnosis so that early treatment can be started before irreversible organ damage occurs.

CASE PRESENTATION

A previously fit and well 32-year-old Caucasian male presented with multisystem dysfunction including renal impairment. Although he had no suggestive symptoms, a diagnosis of Fabry disease was first established on a native renal biopsy. This was confirmed by enzymatic testing and subsequent genetic analysis that revealed a potentially new pathogenic variant.

CONCLUSIONS

This case highlights the importance both of Fabry disease as a differential diagnosis in patients with renal impairment in the context of multi-system disease and also of adequate tissue sampling for electron microscopy when performing native renal biopsies.