Utility of renal biopsy in the clinical management of renal disease

Demographic distribution analysis of different glomerular diseases in Southwest China from 2008 to 2022

BACKGROUND

Environmental and lifestyle factors play an etiological role in the pathogenesis of different glomerular diseases. Thus, exploring the epidemic characteristics of renal disease in different nationalities and regions is important.

MATERIALS AND METHODS

Patients who underwent renal biopsy from October 2008 to October 2022 were included. The proportion and change tendency of glomerular diseases and the differences between the sexes and different ages and races were analyzed.

RESULTS

There were 15,146 cases of glomerular diseases (98.5%), involving 7538 males (49.8%) and 7608 females (50.2%). The mean age was 37.0 years (range 0-80 years). The proportion of membranous nephropathy (MN) and diabetic nephropathy (DN) showed an increased trend. The most common primary glomerulonephritis (PGN) was IgA nephropathy (IgAN, 44.6%), followed by minimal-change disease (MCD, 24.3%) and MN (15.4%). Lupus nephritis (LN, 30%) accounted for the largest proportion of SGNs, followed by Henoch-Schonlein purpura nephritis (HSPN, 20.9%) and DN (19.8%). Compared with adults aged 18-60 years old, MCD and HSPN were more common in children and MN and DN in elderly individuals, statistically significant differences. Additionally, the sex and age distribution of PGN and SGN between the Tibetan and Han populations differed significantly, whereby LN was higher in the Han population and HSPN in the Tibetan population.

CONCLUSION

The distribution of glomerular diseases showed age, sex and race differences. This research will be beneficial for providing epidemiological evidence for clinical diagnosis, disease prevention and public health decision-making.

Integrin-linked kinase mRNA expression in circulating mononuclear cells as a biomarker of kidney and vascular damage in experimental chronic kidney disease

BACKGROUND

Traditional biomarkers of chronic kidney disease (CKD) detect the disease in its late stages and hardly predict associated vascular damage. Integrin-linked kinase (ILK) is a scaffolding protein and a serine/threonine protein kinase that plays multiple roles in several pathophysiological processes during renal damage. However, the involvement of ILK as a biomarker of CKD and its associated vascular problems remains to be fully elucidated.

METHODS

CKD was induced by an adenine-rich diet for 6 weeks in mice. We used an inducible ILK knockdown mice (cKD-ILK) model to decrease ILK expression. ILK content in mice's peripheral blood mononuclear cells (PBMCs) was determined and correlated with renal function parameters and with the expression of ILK and fibrosis and inflammation markers in renal and aortic tissues. Also, the expression of five miRNAs that target ILK was analyzed in whole blood of mice.

RESULTS

The adenine diet increased ILK expression in PBMCs, renal cortex, and aortas, and creatinine and urea nitrogen concentrations in the plasma of WT mice, while these increases were not observed in cKD-ILK mice. Furthermore, ILK content in PBMCs directly correlated with renal function parameters and with the expression of renal and vascular ILK and fibrosis and inflammation markers. Finally, the expression of the five miRNAs increased in the whole blood of adenine-fed mice, although only four correlated with plasma urea nitrogen, and of those, three were downregulated in cKD-ILK mice.

CONCLUSIONS

ILK, in circulating mononuclear cells, could be a potential biomarker of CKD and CKD-associated renal and vascular damage.

Assessment of the Added Value of Intravoxel Incoherent Motion Diffusion-Weighted MR Imaging in Identifying Non-Diabetic Renal Disease in Patients With Type 2 Diabetes Mellitus

BACKGROUND

Identification of non-diabetic renal disease (NDRD) in patients with type 2 diabetes mellitus (T2DM) may help tailor treatment. Intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI) is a promising tool to evaluate renal function but its potential role in the clinical differentiation between diabetic nephropathy (DN) and NDRD remains unclear.

PURPOSE

To investigate the added role of IVIM-DWI in the differential diagnosis between DN and NDRD in patients with T2DM.

STUDY TYPE

Prospective.

POPULATION

Sixty-three patients with T2DM (ages: 22-69 years, 17 females) confirmed by renal biopsy divided into two subgroups (28 DN and 35 NDRD).

FIELD STRENGTH/SEQUENCE

3 T/ T2 weighted imaging (T2WI), and intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI).

ASSESSMENT

The parameters derived from IVIM-DWI (true diffusion coefficient [D], pseudo-diffusion coefficient [D*], and pseudo-diffusion fraction [f]) were calculated for the cortex and medulla, respectively. The clinical indexes related to renal function (eg cystatin C, etc.) and diabetes (eg diabetic retinopathy [DR], fasting blood glucose, etc.) were measured and calculated within 1 week before MRI scanning. The clinical model based on clinical indexes and the IVIM-based model based on IVIM parameters and clinical indexes were established and evaluated, respectively.

STATISTICAL TESTS

Student's t-test; Mann-Whitney U test; Fisher's exact test; Chi-squared test; Intraclass correlation coefficient; Receiver operating characteristic analysis; Hosmer-Lemeshow test; DeLong's test. P < 0.05 was considered statistically significant.

RESULTS

The cortex D*, DR, and cystatin C values were identified as independent predictors of NDRD in multivariable analysis. The IVIM-based model, comprising DR, cystatin C, and cortex D*, significantly outperformed the clinical model containing only DR, and cystatin C (AUC = 0.934, 0.845, respectively).

DATA CONCLUSION

The IVIM parameters, especially the renal cortex D* value, might serve as novel indicators in the differential diagnosis between DN and NDRD in patients with T2DM.

EVIDENCE LEVEL

2 TECHNICAL EFFICACY: Stage 2.

Radiomics Machine Learning Analysis of Clear Cell Renal Cell Carcinoma for Tumour Grade Prediction Based on Intra-Tumoural Sub-Region Heterogeneity

BACKGROUND

Renal cancers are among the top ten causes of cancer-specific mortality, of which the ccRCC subtype is responsible for most cases. The grading of ccRCC is important in determining tumour aggressiveness and clinical management.

OBJECTIVES

The objectives of this research were to predict the WHO/ISUP grade of ccRCC pre-operatively and characterise the heterogeneity of tumour sub-regions using radiomics and ML models, including comparison with pre-operative biopsy-determined grading in a sub-group.

METHODS

Data were obtained from multiple institutions across two countries, including 391 patients with pathologically proven ccRCC. For analysis, the data were separated into four cohorts. Cohorts 1 and 2 included data from the respective institutions from the two countries, cohort 3 was the combined data from both cohort 1 and 2, and cohort 4 was a subset of cohort 1, for which both the biopsy and subsequent histology from resection (partial or total nephrectomy) were available. 3D image segmentation was carried out to derive a voxel of interest (VOI) mask. Radiomics features were then extracted from the contrast-enhanced images, and the data were normalised. The Pearson correlation coefficient and the XGBoost model were used to reduce the dimensionality of the features. Thereafter, 11 ML algorithms were implemented for the purpose of predicting the ccRCC grade and characterising the heterogeneity of sub-regions in the tumours.

RESULTS

For cohort 1, the 50% tumour core and 25% tumour periphery exhibited the best performance, with an average AUC of 77.9% and 78.6%, respectively. The 50% tumour core presented the highest performance in cohorts 2 and 3, with average AUC values of 87.6% and 76.9%, respectively. With the 25% periphery, cohort 4 showed AUC values of 95.0% and 80.0% for grade prediction when using internal and external validation, respectively, while biopsy histology had an AUC of 31.0% for the classification with the final grade of resection histology as a reference standard. The CatBoost classifier was the best for each of the four cohorts with an average AUC of 80.0%, 86.5%, 77.0% and 90.3% for cohorts 1, 2, 3 and 4 respectively.

CONCLUSIONS

Radiomics signatures combined with ML have the potential to predict the WHO/ISUP grade of ccRCC with superior performance, when compared to pre-operative biopsy. Moreover, tumour sub-regions contain useful information that should be analysed independently when determining the tumour grade. Therefore, it is possible to distinguish the grade of ccRCC pre-operatively to improve patient care and management.

Enhancement of Classifier Performance with Adam and RanAdam Hyper-Parameter Tuning for Lung Cancer Detection from Microarray Data-In Pursuit of Precision

Microarray gene expression analysis is a powerful technique used in cancer classification and research to identify and understand gene expression patterns that can differentiate between different cancer types, subtypes, and stages. However, microarray databases are highly redundant, inherently nonlinear, and noisy. Therefore, extracting meaningful information from such a huge database is a challenging one. The paper adopts the Fast Fourier Transform (FFT) and Mixture Model (MM) for dimensionality reduction and utilises the Dragonfly optimisation algorithm as the feature selection technique. The classifiers employed in this research are Nonlinear Regression, Naïve Bayes, Decision Tree, Random Forest and SVM (RBF). The classifiers' performances are analysed with and without feature selection methods. Finally, Adaptive Moment Estimation (Adam) and Random Adaptive Moment Estimation (RanAdam) hyper-parameter tuning techniques are used as improvisation techniques for classifiers. The SVM (RBF) classifier with the Fast Fourier Transform Dimensionality Reduction method and Dragonfly feature selection achieved the highest accuracy of 98.343% with RanAdam hyper-parameter tuning compared to other classifiers.

Shear wave elastography in chronic kidney disease - the physics and clinical application

Chronic kidney disease is a leading public health problem worldwide. The global prevalence of chronic kidney disease is nearly five hundred million people, with almost one million deaths worldwide. Estimated glomerular filtration rate, imaging such as conventional ultrasound, and histopathological findings are necessary as each technique provides specific information which, when taken together, may help to detect and arrest the development of chronic kidney disease, besides managing its adverse outcomes. However, estimated glomerular filtration rate measurements are hampered by substantial error margins while conventional ultrasound involves subjective assessment. Although histopathological assessment is the best tool for evaluating the severity of the renal pathology, it may lead to renal insufficiency and haemorrhage if complications occurred. Ultrasound shear wave elastography, an emerging imaging that quantifies tissue stiffness non-invasively has gained interest recently. This method applies acoustic force pulses to generate shear wave within the tissue that propagate perpendicular to the main ultrasound beam. By measuring the speed of shear wave propagation, the tissue stiffness is estimated. This paper reviews the literature and presents our combined experience and knowledge in renal shear wave elastography research. It discusses and highlights the confounding factors on shear wave elastography, current and future possibilities in ultrasound renal imaging and is not limited to new sophisticated techniques.

A web-based tool for real-time adequacy assessment of kidney biopsies

The escalating incidence of kidney biopsies providing insufficient tissue for diagnosis poses a dual challenge, straining the healthcare system and jeopardizing patients who may require rebiopsy or face the prospect of an inaccurate diagnosis due to an unsampled disease. Here, we introduce a web-based tool that can provide real-time, quantitative assessment of kidney biopsy adequacy directly from photographs taken with a smartphone camera. The software tool was developed using a deep learning-driven automated segmentation technique, trained on a dataset comprising nephropathologist-confirmed annotations of the kidney cortex on digital biopsy images. Our framework demonstrated favorable performance in segmenting the cortex via 5-fold cross-validation (Dice coefficient: 0.788±0.130) (n=100). Offering a bedside tool for kidney biopsy adequacy assessment has the potential to provide real-time guidance to the physicians performing medical kidney biopsies, reducing the necessity for re-biopsies. Our tool can be accessed through our web-based platform: http://www.biopsyadequacy.org.

Diagnostic performance of renal cortical elasticity by supersonic shear wave imaging in pediatric glomerular disease

PURPOSE

To explore the diagnostic performance of renal cortical elasticity expressed by Young's modulus (YM) using the supersonic shear wave imaging (SSI) technique in pediatric glomerular disease.

MATERIALS AND METHODS

Seventy-one children with glomerular disease confirmed by renal biopsy and sixty healthy volunteers were enrolled in this study. Conventional and SSI ultrasound examinations were performed in all individuals for both kidneys. We measured renal length, renal width, renal thickness, parenchyma thickness, interlobar arterial resistive index (RI) and the YM of the middle and lower pole.

RESULTS

Regardless of which pole and which side of the kidney, the YM in the disease group was significantly higher than that in the control group (P < 0.001). The YM of the middle pole in the left kidney demonstrated the largest AUC (0.936, P < 0.001), and the corresponding cut-off value was 15.48 kPa with a sensitivity of 87.3% and a specificity of 86.7%. There was no significant difference in the YM among different pathological types of pediatric glomerular disease in the disease group, and the same in different grades of patients with Immunoglobulin A (IgA) nephropathy by Lee classification and the Oxford Classification as well as Henoch-Schonlein purpura nephritis (HSPN) by International Study of Kidney Disease in Children (ISKDC) classification (P > 0.05). We found positive but weak correlations between the YM and renal length (r = 0.299, P = 0.001), renal width (r = 0.408, P < 0.001), renal thickness (r = 0.299, P = 0.001), and parenchyma thickness (r = 0.212, P = 0.015), whereas the YM had no significant correlations with age, sex, BMI, interlobar arterial RI, and laboratory findings (P > 0.05).

CONCLUSIONS

SSI technology is a non-invasive and feasible method for the diagnosis of pediatric glomerular disease. However, SSI did not show good performance in distinguishing different pathological types and disease grades in our study.

A Brief Review of Diagnostic Techniques and Clinical Management in Chronic Kidney Disease

Given its increasing incidence and detrimental effects on life expectancy and quality of life, chronic kidney disease (CKD) is a significant worldwide health concern. This review article provides a complete summary of current information on the diagnosis and management of CKD, focusing on recent advances and innovative approaches. The article discusses the most current findings on CKD risk assessment, emphasizing the need for early diagnosis utilizing better biomarkers and predictive models. A rigorous examination of diagnostic tools such as albumin-to-creatinine ratio (ACR) in urine and glomerular filtration rate (GFR) highlights their importance in determining CKD phases and etiologies. In terms of therapy, the study explores evidence-based techniques to reduce the development of CKD, such as enhanced blood pressure control, glycemic management in diabetic patients, dietary changes, and renin-angiotensin-aldosterone system (RAAS) blocking. Novel therapeutic approaches, including antifibrotic and precision medicine, are evaluated regarding their potential to revolutionize CKD treatment. The study also underlines the need for multidisciplinary therapy and patient education to achieve the best possible CKD patient outcomes. It also highlights the financial and social effects of CKD, highlighting the importance of early treatment to lower medical expenses and enhance the patient's standard of living. Finally, this review article provides a comprehensive update on CKD diagnosis and treatment, highlighting present successes alongside future potential. It is a valuable resource for healthcare professionals, academics, and policymakers who want to improve CKD treatment methods and patient outcomes.

Performance and Advancement of the Kidney Solid Organ Response Test

BACKGROUND

The kidney solid organ response test (kSORT) has been investigated for the prediction of acute rejection in kidney transplant recipients with conflicting results. We aimed to investigate if the kSORT assay score is associated with rejection or immune quiescence.

METHODS

The blinded association between rejection and kSORT > 9 were investigated. Optimization of kSORT prediction was evaluated after unblinding to determine the optimal prediction cutoff value of kSORT score. Additionally, the predictive capability of the kSORT gene set was assessed using blinded normalized gene expression data from microarray (Affymetrix) and qPCR assays.

RESULTS

Of the 95 blood samples analyzed, 18 patients had blood samples before transplant, 77 patients after transplant and 71 had clinically indicated biopsies of which 15 biopsies showed acute rejection and 16 showed chronic active antibody-mediated rejection. When 31 patients with rejection were compared to the remaining 64 patients, positive predictive value (PPV) was 54.29% and negative predictive value (NPV) was 75% when stratified using a kSORT score > 9, and PPV was 57.89% and NPV was 78.95% when stratified using a kSORT score > 5. Using the kSORT assay for detection of rejection showed an area under the curve value of 0.71. Microarray data improved prediction accuracy with PPV of 53% and NPV of 84% compared to qPCR results (PPV and NPV were 36% and 66%), respectively.

CONCLUSIONS

The kSORT assay has the potential to be used as a predictive tool for active rejection and/or immune quiescence, but additional studies will be useful in improving and refining the kSORT assay, in particular the prediction algorithm.

Efficacy and Safety of CT-Guided Kidney Biopsy for the Diagnosis of Glomerular Diseases in Complicated Patients

INTRODUCTION

Kidney biopsy is the cornerstone for the diagnosis of glomerular diseases and to guide treatment. Percutaneous ultrasound-guided kidney biopsy is currently the gold standard to obtain cortical specimens. However, in cases where ultrasound-guided kidney biopsy is not deemed safe (obese patients, deep kidneys, or kidneys with a complicated anatomy), CT-guided kidney biopsy could be a convenient alternative to obtain renal tissue samples. The aim of this study was to describe the diagnostic yield and complications of CT-guided kidney biopsies in patients with glomerular diseases that were previously discarded for ultrasound-guided kidney biopsy.

MATERIAL AND METHODS

We performed a retrospective, single-center, observational study including patients who underwent CT-guided native kidney biopsies in our center after being contraindicated for ultrasound-guided biopsy. Patients' records were reviewed retrieving baseline characteristics and pre-biopsy clinical, laboratory parameters and concomitant medication. The biopsy needle gauge, site of puncture, and number of needle passes were recorded. The diagnostic yield was evaluated by the number of glomeruli obtained, the rate of specimens that were adequate to reach diagnosis, and the number of biopsies that had to be repeated. Complications were defined as minor (hypotension, hematoma) and major (arteriovenous fistulae, major bleeding requiring embolization, or nephrectomy). The diagnostic yield and complications were compared to ultrasound-guided native kidney biopsies performed during the same period.

RESULTS

56 CT-guided native kidney biopsies were performed during the study period. The number of glomeruli obtained per patient was 11.5 ± 6.3, which was inferior to that obtained from ultrasound-guided biopsies (14.08 ± 8.47, p < 0.05). However, the rate of specimens that were adequate to reach a diagnosis was similar (92.9% vs. 90.8%, p = 0.437). The number of needle passes was higher in CT-guided kidney biopsies (2.0 ± 0.7 vs. 1.7 ± 0.5, p < 0.05), as well as the incidence of post-biopsy perirenal asymptomatic hematomas (66.1% vs. 24.5%, p < 0.01). There were no significant differences in other post-biopsy minor complications (1.8% vs. 2.5%, p = 0.621). There were no major complications after CT-guided kidney biopsies.

CONCLUSIONS

CT-guided percutaneous kidney biopsy is a valid alternative for the diagnosis of glomerular diseases in patients with special characteristics such as obesity or deep kidneys that contraindicate ultrasound-guided biopsy. In this population, CT-guided kidney biopsies are safe and provide a high diagnostic yield, reaching a diagnosis in >90% of patients that had been previously discarded for ultrasound-guided biopsy.

Ultrasound elastography in chronic kidney disease: a systematic review and meta-analysis

Ultrasound elastography (USE) is a noninvasive technique for assessing tissue elasticity, and its application in nephrology has aroused growing interest in recent years. The purpose of this article is to systematically review the clinical application of USE in patients with chronic kidney disease (CKD), including native and transplanted kidneys, and quantitatively investigate differences in elasticity values between healthy individuals and CKD patients. Furthermore, we provide a qualitative analysis of the studies included, discussing the potential interplay between renal stiffness, estimated glomerular filtration rate, and fibrosis. In January 2022, a systematic search was carried out on the MEDLINE (PubMed) database, concerning studies on the application of USE in patients with CKD, including patients with transplanted kidneys. The results of the included studies were extracted by two independent researchers and presented mainly through a formal narrative summary. A meta-analysis of nine study parts from six studies was performed. A total of 647 studies were screened for eligibility and, after applying the exclusion and inclusion criteria, 69 studies were included, for a total of 6728 patients. The studies proved very heterogeneous in terms of design and results. The shear wave velocity difference of - 0.82 m/s (95% CI: - 1.72-0.07) between CKD patients and controls was not significant. This result agrees with the qualitative evaluation of included studies that found controversial results for the relationship between renal stiffness and glomerular filtration rate. On the contrary, a clear relationship seems to emerge between USE values and the degree of fibrosis. At present, due to the heterogeneity of results and technical challenges, large-scale application in the monitoring of CKD patients remains controversial.

Molecular MR Imaging of Renal Fibrogenesis in Mice

BACKGROUND

In most CKDs, lysyl oxidase oxidation of collagen forms allysine side chains, which then form stable crosslinks. We hypothesized that MRI with the allysine-targeted probe Gd-oxyamine (OA) could be used to measure this process and noninvasively detect renal fibrosis.

METHODS

Two mouse models were used: hereditary nephritis in Col4a3-deficient mice (Alport model) and a glomerulonephritis model, nephrotoxic nephritis (NTN). MRI measured the difference in kidney relaxation rate, ΔR1, after intravenous Gd-OA administration. Renal tissue was collected for biochemical and histological analysis.

RESULTS

ΔR1 was increased in the renal cortex of NTN mice and in both the cortex and the medulla of Alport mice. Ex vivo tissue analyses showed increased collagen and Gd-OA levels in fibrotic renal tissues and a high correlation between tissue collagen and ΔR1.

CONCLUSIONS

Magnetic resonance imaging using Gd-OA is potentially a valuable tool for detecting and staging renal fibrogenesis.

Assessment of Renal Fibrosis in Patients With Chronic Kidney Disease Using Shear Wave Elastography and Clinical Features: A Random Forest Approach

OBJECTIVE

Renal fibrosis is the common pathological hallmark of chronic kidney disease (CKD) progression. In this study, a random forest (RF) classifier based on 2-D shear wave elastography (SWE) and clinical features for the differential severity of renal fibrosis in patients with CKD is proposed.

METHODS

A total of 162 patients diagnosed with CKD who underwent 2-D SWE and renal biopsy were prospectively enrolled from April 2019 to December 2021 and then randomized into training (n = 114) and validation (n = 48) cohorts at a ratio of 7:3. The least absolute shrinkage and selection operator (LASSO) regression and recursive feature elimination for support vector machines (SVM-RFE) algorithm were employed to select renal fibrosis-related features from clinical information and elastosonographic findings. An RF model was subsequently constructed using the aforementioned informative parameters in the training cohort and evaluated in terms of discrimination, calibration and clinical utility in both cohorts.

RESULTS

The LASSO and SVM-RFE analyses revealed that age, sex, blood urea nitrogen, renal resistive index, hypertension and the 2D-SWE value were independent risk variables associated with renal fibrosis severity. The established RF model incorporating these six variables exhibited fine discrimination in both the derivation (area under the curve [AUC]: 0.84, 95% confidence interval [CI]: 0.76-0.91) and validation (AUC: 0.88, 95% CI: 0.77-0.98) cohorts. Moreover, the calibration curve revealed satisfactory predictive accuracy, and the decision curve analysis revealed a significant clinical net benefit.

CONCLUSION

The developed RF model, via a combination of the 2-D SWE value and clinical information, indicated satisfactory diagnostic performance and clinical practicality toward differentiating moderate-severe from mild renal fibrosis, which may provide critical insight into risk stratification for patients with CKD.

Factors Associated with Glomerular Yield in Percutaneous Kidney Biopsy

Percutaneous kidney biopsy is essential for diagnosing various kidney diseases. However, insufficient glomerular yield leads to misdiagnosis, a critical problem. We retrospectively investigated the risk of insufficient glomerular yield in percutaneous kidney biopsies. We included 236 patients who underwent percutaneous kidney biopsies between April 2017 and September 2020. We retrospectively analyzed the relationship between glomerular yield and patient characteristics. After the biopsy, 31 patients produced insufficient glomerular yields (cases with yielded glomeruli <10). Glomerular yield correlated negatively with hypertension (β = -0.13, p = 0.04), and positively with glomerular density (β = 0.59, p < 0.0001) and the volume of the biopsy core (number of punctures, number of biopsy cores, total length of biopsy core, length of core collected by one puncture, and cortical length). Patients yielding <10 glomeruli had lower glomerular densities (14.4 ± 1.6 vs. 22.9 ± 0.6/cm; p < 0.0001). These results suggest that glomerular density is crucial to glomerular yield. Furthermore, glomerular density was negatively correlated with hypertension, diabetes, and age. Hypertension was independently associated with low glomerular density (β = -0.16, p = 0.02). Thus, the glomerular yield was associated with glomerular density and biopsy core length, and hypertension might be related to glomerular yield via low glomerular density.

Ex vivo confocal microscopy detects basic patterns of acute and chronic lesions using fresh kidney samples

BACKGROUND

Ex vivo confocal microscopy is a real-time technique that provides high-resolution images of fresh, non-fixed tissues, with an optical resolution comparable to conventional pathology. The objective of this study was to investigate the feasibility of using ex vivo confocal microscopy in fusion mode (FuCM) and the haematoxylin and eosin (H&E)-like digital staining that results for the analysis of basic patterns of lesion in nephropathology.

METHODS

Forty-eight renal samples were scanned in a fourth-generation ex vivo confocal microscopy device. Samples were subjected to confocal microscopy imaging and were then processed using conventional pathology techniques. Concordance between the techniques was evaluated by means of the percentage of agreement and the κ index.

RESULTS

Agreement between conventional microscopy and H&E-like digital staining was strong (κ = 0.88) in the evaluation of acute tubular damage and was substantial (κ = 0.79) in the evaluation of interstitial fibrosis, interstitial inflammation, arterial and arteriolar lesions. H&E-like digital staining also allows rapid identification of extracapillary proliferation (κ = 0.88), necrosis and segmental sclerosis (κ = .88) in the glomerular compartment, but the results reported here are limited because of the small number of cases with these glomerular findings.

CONCLUSIONS

FuCM proved to be as effective as conventional techniques in evaluating the presence of acute tubular necrosis and interstitial fibrosis changes, but in fresh tissue. The ease of acquisition of ex vivo confocal microscopy images suggests that FuCM may be useful for rapid evaluation of kidney biopsies and to restructure the clinical workflow in renal histopathology.

Targeted MRM Quantification of Urinary Proteins in Chronic Kidney Disease Caused by Glomerulopathies

Glomerulopathies with nephrotic syndrome that are resistant to therapy often progress to end-stage chronic kidney disease (CKD) and require timely and accurate diagnosis. Targeted quantitative urine proteome analysis by mass spectrometry (MS) with multiple-reaction monitoring (MRM) is a promising tool for early CKD diagnostics that could replace the invasive biopsy procedure. However, there are few studies regarding the development of highly multiplexed MRM assays for urine proteome analysis, and the two MRM assays for urine proteomics described so far demonstrate very low consistency. Thus, the further development of targeted urine proteome assays for CKD is actual task. Herein, a BAK270 MRM assay previously validated for blood plasma protein analysis was adapted for urine-targeted proteomics. Because proteinuria associated with renal impairment is usually associated with an increased diversity of plasma proteins being present in urine, the use of this panel was appropriate. Another advantage of the BAK270 MRM assay is that it includes 35 potential CKD markers described previously. Targeted LC-MRM MS analysis was performed for 69 urine samples from 46 CKD patients and 23 healthy controls, revealing 138 proteins that were found in ≥2/3 of the samples from at least one of the groups. The results obtained confirm 31 previously proposed CKD markers. Combination of MRM analysis with machine learning for data processing was performed. As a result, a highly accurate classifier was developed (AUC = 0.99) that enables distinguishing between mild and severe glomerulopathies based on the assessment of only three urine proteins (GPX3, PLMN, and A1AT or SHBG).

Diagnostic challenges of renal medullary carcinoma and the role for cytologic assessment: Case report and literature review

BACKGROUND

Renal medullary carcinoma (RMC) is a diagnostically challenging, aggressive primary renal malignancy associated with abysmal survival. Delays in diagnosis contribute to most patients having diffusely metastatic disease at the time of initial presentation.

METHODS

We present the case of a 13-year-old African American male with sickle cell trait who presented with a renal mass and hematuria. Evaluation included imaging, fluid cultures, and cytologic assessment.

RESULTS

Patient was diagnosed with RMC based on cytologic assessment of sub-centimeter fluid collections aspirated from the left kidney at the time of cortical biopsy for suspected renal mass. The additional fluid aspiration in conjunction with renal biopsy was an atypical but crucial step in early diagnosis.

CONCLUSION

Cytomorphologic evaluation of fluid biospecimens is not currently part of the standard work-up for patients with renal masses but, when available, can provide crucial information that reduces time to diagnosis. Prompt symptom recognition and treatment initiation may improve patient outcomes.

Effects of receiving renal biopsy on the prognosis of chronic kidney disease patients with impaired renal function

BACKGROUND

Impaired renal function was not a recognized indication for renal biopsy. The effects of receiving renal biopsy on the renal functional prognosis for chronic kidney disease (CKD) patients with impaired renal function need to be explored.

METHODS

This study retrospectively enrolled 300 renal function impaired CKD patients in Renji Hospital from January 2015 to December 2017, 150 of them received percutaneous renal biopsy while the others did not. The endpoint was ≥ 50% estimated glomerular filtration rate (eGFR) decline from baseline or development of end-stage renal disease (ESRD). Kaplan-Meier analysis with log-rank test was performed to compare the renal survival probability between patients receiving renal biopsy or not. Univariate and multivariate analysis with Cox regression were conducted with predictors of poor renal outcomes in the study cohort.

RESULTS

The median follow-up period was 37.6 months. During the follow-up period, the eGFR of the biopsy group increased from 52.2 ± 14.4 to 67.4 ± 37.8 ml/min/1.73 m², but decreased from 55.3 ± 17.1 to 29.8 ± 19.1 ml/min/1.73 m² in the non-biopsy group. Patients who received renal biopsy had significantly higher renal survival probability (P < 0.001). Cox regression analysis revealed that 24-hour urine protein excretion (24 h UPE) more than 1 g/d was an independent predictor for poor renal outcomes in the non-biopsy group but not in the renal biopsy group (HR = 1.719, P = 0.040).

CONCLUSION

CKD patients with impaired renal function are recommended to receive renal biopsy to make pathological diagnoses, especially for those with the 24-hour urine protein excretion more than 1 g/d.

The impact of blood pressure on the risk of postbiopsy bleeding during the whole procedure of percutaneous kidney biopsy

PURPOSE

To investigate whether BP is related to postbiopsy bleeding in patients undergoing native percutaneous kidney biopsy (PKB) and to evaluate the dynamic changes in blood pressure (BP) pre- and post-kidney biopsy.

METHODS

A retrospective cross-sectional study was conducted. The whole-procedural systolic (SBP) and diastolic (DBP) BP for patients undergoing ultrasound-guided native PKB from October 2017 to December 2020 were recorded in the study. Propensity score matching was used to minimize selection bias. SBP and DBP were analyzed as the main risk factors for bleeding complications. Receiver operating characteristic (ROC) curves were employed to explore the optimal BP thresholds to differentiate between bleeding and nonbleeding. The rates of major bleeding complications were analyzed according to BP thresholds through logistic analysis.

RESULTS

Of 1146 biopsies, 432 (37.7%) patients suffered from postbiopsy bleeding, 88 (7.7%) patients had major bleeding complications, and 344 (30.0%) patients had minor bleeding complications. In the original data, for patients with SBP ≥ 160 mmHg before PKB, the rate of major bleeding complications was 17.6% (7.5% for SBP < 160 mmHg), and the rate of major bleeding complications was 19.0% in patients with DBP ≥ 100 mmHg (7.5% for DBP < 100 mmHg). For patients with DBP ≥ 85 mmHg to 100 mmHg after PKB, the rate of major bleeding complications ranged from 9.5 to 17.5%. The rate of major bleeding complications was lower (6.6-7.3%) in patients with DBP < 100 mmHg to 85 mmHg.

CONCLUSION

Patients who have high-level BP during the native PKB perioperative period are at higher risk for postbiopsy bleeding. High-level BP here does not refer to traditional hypertension according to the guidelines for the diagnosis and treatment of hypertension, but rather BP above a certain threshold related to bleeding risk.

Urinary T Cells Identify Renal ANCA-Associated Vasculitis and Predict Prognosis: a proof of concept study

Introduction

Necrotizing crescentic glomerulonephritis is a major contributor to morbidity and mortality in Antineutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV). Because therapy relies on immunosuppressive agents with potentially severe adverse effects, a reliable noninvasive biomarker of disease activity is needed to guide treatment.

Methods

We used flow cytometry to quantify T cell subsets in blood and urine samples from 95 patients with AAV and 8 controls to evaluate their biomarker characteristics. These were compared to soluble markers, monocyte chemoattractant protein-1 (MCP-1), soluble CD163 (sCD163), soluble CD25 (sCD25), and complement C5a (C5a), measured using multiplex analysis. Available kidney biopsies (n = 21) were classified according to Berden.

Results

Patients with active renal AAV (rAAV) showed significantly higher urinary cell counts than those in remission, or those with extrarenal manifestation, or healthy controls. Urinary T cells showed robust discrimination of disease activity with superior performance compared to MCP-1 and sCD163. Patients whose kidney biopsies had been classified as "crescentic" according to Berden classification showed higher urinary T cell counts. Discordant regulatory T cells (T_reg) proportions and CD4⁺/CD8⁺ ratio in blood and urine suggested that urinary cells reflect tissue migration rather than mere micro-bleeding. Furthermore, urinary T_reg and T helper cells (T_H17) patterns were associated with clinical response and risk of renal relapse.

Conclusion

Urinary T cells reflect the renal inflammatory milieu in AAV and provide further insights into the pathogenesis of this chronic condition. Their promising potential as noninvasive diagnostic and prognostic biomarkers deserves further exploitation.

Determination of Anti-Phospholipase A2 and Anti-Thrombospondin Type 1 Domain-Containing Protein 7A in Latin Patients with Membranous Nephropathy

Primary membranous nephropathy (MN) is caused by antibodies against podocyte antigens, especially the type M receptor of phospholipase A2 (PLA2R) and thrombospondin type-1 domain containing 7 A (THSD7A). This study's aim was the determination of anti-PLA2R, anti-THSD7A serum antibodies, and anti-PLA2R renal tissue staining prevalence in a Latin population with MN, as well as evaluating their role as biomarkers for disease activity. The performance of the two anti-PLA2R serum diagnostic methods-ELISA and indirect immunofluorescence (IFI)-was evaluated for the diagnosis of MN. Fifty-nine patients, including 29 with MN, 18 with lupus membranous nephropathy (LMN) and 12 with focal and segmental glomerulosclerosis (FSGS), were evaluated for serum antibodies. Renal biopsies were also evaluated for the presence of anti-PLA2R staining. Twenty-one patients with MN were followed for 1 year. Patients with LMN and FSGS were negative for both antibodies. All 29 MN patients were negative for anti-THSD7A; 16 MN patients were positive for anti-PLA2R by ELISA and/or IFI, and 3 MN patients were positive for anti-PLA2R only by IFI. Thus, the anti-PLA2R ELISA test demonstrated 45% sensitivity and 97% specificity, while the IFI test showed, respectively, 55% and 100% in our MN patients. Among the 28 MN renal biopsies, 20 presented anti-PLA2R positive staining, corresponding to a 72% sensitivity. Positive correlations were observed between the anti-PLA2R ELISA titer and proteinuria. In conclusion, determination of anti-PLA2R antibodies in the MN Latin population showed similar rates to those reported for other populations. The anti-PLA2R serum levels correlated with MN disease activity.

Identifying stable reference genes in polyethene glycol precipitated urinary extracellular vesicles for RT-qPCR-based gene expression studies in renal graft dysfunction patients

BACKGROUND

Urinary extracellular vesicles (UEVs) hold RNA in their cargo and are potential sources of biomarkers for gene expression studies. The most used technique for gene-expression studies is quantitative polymerase chain reaction (qPCR). It is critical to use stable reference genes (RGs) as internal controls for normalising gene expression data, which aren't currently available for UEVs.

METHODS

UEVs were precipitated from urine of graft dysfunction patients and healthy controls by Polyethylene glycol, Mn6000 (PEG6K). Vesicular characterisation confirmed the presence of UEVs. Gene expression levels of five commonly used RGs, i.e., Beta-2-Microglobulin (B2M), ribosomal-protein-L13a (RPL13A), Peptidylprolyl-Isomerase-A (PPIA), hydroxymethylbilane synthase (HMBS), and glyceraldehyde-3-phosphate-dehydrogenase (GAPDH) were quantified, and their stability was established through the RefFinder. The stability of identified RGs was validated by quantification of Perforin and granzyme B, signature molecules of renal graft dysfunction.

RESULTS

Urine precipitated with 12% 6 K PEG yielded round and double-membraned UEVs of size ranging from 30 to 100 nm, as confirmed through transmission electron microscopy. Nanoparticle tracking analysis (59 ± 22 nm) and Dynamic-light-scattering (78 ± 56.5 nm) confirmed their size profile. Semi-quantitative Exocheck antibody array demonstrated the presence of EV protein markers in UEV. Using the comparative ΔCт method and RefFinder analysis, B2M (1.6) and RPL13A (1.8) genes emerged as the most stable reference genes. Validation of target gene expression in renal graft dysfunction patients confirmed the efficiency of B2M and RPL13A through significant upregulation compared to other RGs.

CONCLUSIONS

Our study identified and validated B2M and RPL13A as optimal RGs for mRNA quantification studies in the UEVs of patients with renal graft dysfunction.

Efficacy and safety of percutaneous renal biopsy performed using 18G needle versus 16G needle: a single-center retrospective study

Background

At present, both 16G and 18G needles are used for percutaneous renal biopsy in China. This study aimed to compare the efficacy and safety of biopsy performed with the 18G needle vs. the 16G needle.

Methods

The data of patients who underwent percutaneous renal biopsy at our hospital between January 2015 and December 2019 were retrospectively analyzed. The number of glomeruli obtained by puncture and postoperative complications were compared between patients undergoing biopsy with the 16G and 18G needles. Continuous variables were compared by the t test or the Mann–Whitney U test, and categorical variables by the chi-square test. Correlation analysis was used to examine the relationship of different variables with hematoma size.

Results

Of the total 3138 kidney biopsies, 2526 were performed with the18G needle and 612 with the 16G needle. The number of glomeruli obtained was not significantly different between the two groups (P = 0.078). Large hematomas were significantly more common the 16G group than in the 18G group (9.31% vs. 5.98%, P = 0.003). Arteriovenous fistula was also more common in the 16G group (1.14% vs. 0.23%, P = 0.005). Other complications were rare, with similar incidence in the two groups.

Conclusion

The 18G needle is as effective as the 16G needle for percutaneous renal biopsy. The risk of large hematoma and arteriovenous fistula appear to be lower with the 18G needle.

Congestive Nephropathy

The complex interaction between cardiac and renal functions is known. However, when these functions are disrupted, many intricate and sensitive interactions between these organs are failed by several pathophysiological ways. As a result, this malfunction is clinically evident by sign and symptoms associated to intravascular and interstitial congestion. In this sense, the adverse impact of venous congestion on renal function has long been recognized. Currently, the presence of a specific subtype of nephropathy associated to congestion has been suggested. Even though no diagnosis criteria has been clearly stablished, and no renal specific histological pattern were reported; studies regarding this issue may help to improve the handling and therapeutic principles in affected patients.

Kidney tissue elastography and interstitial fibrosis observed in kidney biopsy

Introduction

Kidney interstitial fibrosis is an important risk factor for the progression of chronic kidney disease. Kidney elastography is a noninvasive imaging modality that might be used to assess tissue fibrosis. In this study, we aimed to investigate the relationship between tissue stiffness detected in kidney elastography and interstitial fibrosis observed in kidney biopsy.

Materials and methods

Patients who were hospitalized in a tertiary care university hospital with a kidney biopsy indication were included in this study. In all patients, the transverse and sagittal elastography measurements were made using a sonoelastography device before the biopsy. The total histological score was calculated.

Results

Fifty-seven native kidney patients with proteinuria were included in the study. Patients were divided into two groups according to the presence (n = 6) and absence of fibrosis (n = 51) as detected by kidney biopsy. A significant correlation was found between the presence of fibrosis detected by biopsy and elastography outcomes (p = .046, r = .192). A significant correlation was found between the urea and creatinine levels and transverse elastography measurements (p = .036, r = .240). No correlation was observed between the transverse elastography measurements and total histological score consisting of glomerular, vascular, and tubular scores (r = .006, p = .967)

Conclusion

The findings of our study suggest a significant relationship between the elastography measurements and interstitial fibrosis. Because of the high negative predictive value (91%), we suggest that elastography should mainly be used as an exclusion test for the presence of fibrosis. We also believe that elastography may be useful to evaluate the fibrosis status in kidney diseases.

Evaluation of renal fibrosis in patients with chronic kidney disease by shear wave elastography: a comparative analysis with pathological findings

PURPOSE

To explore the elastic values obtained by shear wave elastography (SWE) in assessing renal fibrosis in chronic kidney disease (CKD).

METHODS

One hundred and twenty-four patients with CKD who underwent renal biopsy were prospectively enrolled between April 2019 and June 2021. SWE was performed to measure the renal cortex stiffness, presented as SWE parameters, including the minimum, mean, and maximum elasticity (namely Emin, Emean, and Emax). Then, the patients with different kidney pathological impairment (mild, moderate, and severe groups) were compared in SWE elasticity and the discriminative capacity was also analyzed.

RESULTS

For the pathology impaired grade, SWE parameter was significantly reduced in the moderately and severely impaired group than the mild one. Emax parameter achieved the best discriminative ability toward differentiating moderate-severe impairment from mild one, yielding an area under the curve (AUC) of 0.764 (95%CI: 0.681-0.848). Regarding interstitial fibrosis/tubular atrophy and global glomerular sclerosis, the Emax values were significantly reduced across the group of patients with moderate grade compared to those with mild grade. Patients in severe group were also with reduced elastic value than those in mild one, while the difference was non-significant in interstitial fibrosis/tubular atrophy but a borderline statistical significance was achieved in global glomerular sclerosis. For grade of vessel wall thickening, patients in moderate (33.04 ± 9.86 kPa, P = 0.009) and severe (31.42 ± 9.16 kPa, P < 0.001) group were with significantly lower elastic value compared with those in the mild one (39.58 ± 9.67 kPa). The SWE parameter was linearly reduced as grade of vessel wall thickening elevated (P for trend: < 0.001).

CONCLUSION

SWE derived elastic values reduced as pathology grade of renal fibrosis or grade of vessel wall thickening progresses in patients with CKD, which may be attributed to renal hypo-perfusion rather than tubulo-interstitial fibrosis progression.

Association Between Diabetes and Major Bleeding Complications of Renal Biopsy

Introduction

Nephrologists have recently recognized the heterogeneity of kidney diseases among patients with diabetes and begun to actively perform percutaneous renal biopsies (PRBs). Nevertheless, the association between diabetes and major bleeding complications of PRB remains unclear.

Methods

In this retrospective cohort study using the Diagnosis Procedure Combination database in Japan, we identified patients who underwent an elective PRB from July 2010 to March 2018. The primary outcome was the occurrence of major bleeding complications, defined as red blood cell transfusion within 7 days after PRB or invasive hemostasis after PRB. Multivariable regression analysis was performed to analyze the association between diabetes and major bleeding complications with adjustment for patient and hospital characteristics.

Results

We identified 76,302 patients, including 8245 with diabetes. The proportion of PRBs performed for patients with diabetes continuously increased over time. Major bleeding complications occurred in 678 patients (0.9%), including 622 (0.8%) with red blood cell (RBC) transfusion and 109 (0.1%) with invasive hemostasis. Diabetes was significantly associated with major bleeding complications (relative risk [RR] = 2.41; 95% CI 2.00–2.90). Among patients with diabetes, multiagent or insulin treatment had significant association with major bleeding complications (RR = 1.57; 95% CI 1.18–2.10), compared with single-agent diabetes treatment.

Conclusion

Diabetes is significantly associated with major bleeding complications of PRBs. Moreover, severity of diabetes has association with increases in major bleeding complications. Thus, nephrologists should carefully judge whether the anticipated benefits outweigh the relatively high risk of major bleeding complications when considering PRB for patients with diabetes.

Quantitative Mass Spectrometry Normalization in Urine Biomarker Analysis in Nephrotic Syndrome

Chronic kidney disease (CKD) affects 30 million adults, costs ~$79 billion dollars (2016) in Medicare expenditures, and is the ninth leading cause of death in the United States. The disease is silent or undiagnosed in almost half of people with severely reduced kidney function. Urine provides an ideal biofluid that is accessible to high-sensitivity mass spectrometry-based proteomic interrogation and is an indicator of renal homeostasis. While the accurate and precise diagnosis and better disease management of CKD can be aided using urine biomarkers, their discovery in excessive protein or nephrotic urine samples can present challenges. In this work we present a mass spectrometry-based method utilizing multiplex tandem mass tag (TMT) quantification and improved protein quantification using reporter ion normalization to urinary creatinine to analyze urinary proteins from patients with a form of nephrotic syndrome (FSGS). A comparative analysis was performed for urine from patients in remission versus active disease flare. Two-dimensional LC-MS/MS TMT quantitative analysis identified over 1058 urine proteins, 580 proteins with 2 peptides or greater and quantifiable. Normalization of TMT abundance values to creatinine per ml of urine concentrated reduced variability in 2D-TMT-LC-MS/MS experiments. Univariate and multivariate analyses showed that 27 proteins were significantly increased in proteinuric disease flare. Hierarchical heatmap clustering showed that SERPINA1 and ORM1 were >1.5 fold increased in active disease versus remission urine samples. ELISA validation of SERPINA1 and ORM1 abundance agreed with our quantitative TMT proteomics analysis. These findings provide support for the utility of this method for identification of novel diagnostic markers of CKD and identify SERPINA1 and ORM1 as promising candidate diagnostic markers for FSGS.

Prevention of bleeding after percutaneous biopsy with a small intestinal submucosa hemostatic plug

Percutaneous biopsies (PBs) are the gold standard diagnostic procedures indicated for renal and hepatic disorders. Nevertheless, they can cause hemorrhages and are contraindicated for coagulopathic patients. In this study we designed, fabricated, and evaluated a small intestinal submucosa (SIS) plug to reduce, and potentially cease, bleeding to decrease death risk after percutaneous hepatic and renal biopsies in healthy and coagulopathic in vivo models. First, the plug's blocking capacity was determined with an increase in its diameter of 24 ± 11% after immersion in human blood, and the capacity to induce clotting on its surface. The plug's in vivo performance was evaluated in a healthy porcine model, which showed minimal inflammatory reaction without side effects confirmed by histological results after 30 days. The plug's response in the coagulopathic model was assessed using heparinized swine for 2 days, which revealed localized microhemorrhages and mild inflammatory response without any lesions to the surrounding tissue. No major adverse events nor macroscopic hemorrhages were detected in the animal models. Furthermore, we assessed the plug's efficacy to reduce and stop bleeding using a transplant-discarded human liver model (n = 14). In this case, the mass of blood lost was 43.8 ± 21.8% lower in plugged transplant-discarded human liver biopsies compared to control biopsies without a plug. The bleeding was stopped within three minutes in 92% of plugged cases, but only in 8% of non-plugged cases. We demonstrated the feasibility of making a hemostatic SIS plug, which does not induce major inflammatory reaction and can effectively reduce and stop bleeding after PBs in non-coagulopathic and coagulopathic in vivo models, and in a transplant-discarded human liver model. STATEMENT OF SIGNIFICANCE: Percutaneous biopsy (PB) is a gold standard diagnostic procedure, but it can provoke life-threatening complications and is contraindicated for patients with coagulopathic disorders. This study demonstrates that small intestinal submucosa (SIS) can be manufactured into a biocompatible thrombogenic plug, insertable through a commercial Tru-Cut needle sheath. This device takes advantage of the collagen-rich composition of SIS to stop and reduce bleeding more effectively than the traditional PB, indicating that it could be routinely employed in a traditional biopsy to increase safety, or as a cost and time-reducing alternative to transjugular biopsy for coagulopathic patients.

Nephrologists' Attitudes Toward Native Kidney Biopsy: A Qualitative Study

Rationale & Objective

Although kidney biopsy is a useful tool, nephrologists' approach toward biopsies is inconsistent for reasons incompletely understood, including lack of established clinical guidelines. We examined contemporary clinical decision-making patterns among nephrologists to perform native kidney biopsy.

Study Design

Qualitative study using semistructured interviews.

Setting & Participants

Purposive sampling was used to select nephrologists from different regions in the United States. Semistructured interviews were continued until thematic saturation.

Analytical Approach

A modified grounded theory was used to identify dominant themes reflecting the nephrologists' decision-making styles about kidney biopsy.

Results

Twenty nephrologists were interviewed: 16 (80%) were from academic centers, 3 (15%) performed their own biopsies, and 7 (35%) had been in practice for less than 10 years. The median time of practice was 14 years. We found substantial variability among the nephrologists in their attitude toward using kidney biopsy, which reflected individual differences in weighing the risks and benefits of the procedure for an individual patient. Five overarching themes were identified: operator comfort with biopsy and availability of interventional radiologist, exposure to biopsy during training and years of experience, concerns about the invasiveness of biopsy and inflicting harm, perception of evidence base and limited treatment options, and patient characteristics and preference.

Limitations

Generalizability was limited because the nephrologists sampled may not have been broadly representative.

Conclusions

Multiple factors influence nephrologists' decision to pursue kidney biopsy, with substantial variability among nephrologists that can have meaningful clinical implications. This suggests the need to establish consensus guidelines to make biopsy practice more standardized.

Urinary Protein and Peptide Markers in Chronic Kidney Disease

Chronic kidney disease (CKD) is a non-specific type of kidney disease that causes a gradual decline in kidney function (from months to years). CKD is a significant risk factor for death, cardiovascular disease, and end-stage renal disease. CKDs of different origins may have the same clinical and laboratory manifestations but different progression rates, which requires early diagnosis to determine. This review focuses on protein/peptide biomarkers of the leading causes of CKD: diabetic nephropathy, IgA nephropathy, lupus nephritis, focal segmental glomerulosclerosis, and membranous nephropathy. Mass spectrometry (MS) approaches provided the most information about urinary peptide and protein contents in different nephropathies. New analytical approaches allow urinary proteomic-peptide profiles to be used as early non-invasive diagnostic tools for specific morphological forms of kidney disease and may become a safe alternative to renal biopsy. MS studies of the key pathogenetic mechanisms of renal disease progression may also contribute to developing new approaches for targeted therapy.

Kidney biopsy in very elderly patients: indications, therapeutic impact and complications

BACKGROUND

Few data is available on the risk/benefit balance of native kidney biopsy (KB) in very elderly patients.

METHODS

Multicenter retrospective cohort study in the Aix-Marseille area: the results of KB and medical charts of all patients over 85 years biopsied between January 2010 and December 2018 were reviewed.

RESULTS

104 patients were included. Median age was 87 years. Indications for KB were: acute kidney injury (AKI) in 69.2% of patients, nephrotic syndrome (NS) with AKI in 13.5%, NS without AKI in 12.5%, and proteinuria in 4.8%. Median serum creatinine was 262 μmol/L, 21% of patients required dialysis at the time of KB. Significant bleeding occurred in 7 (6.7%) patients, requiring blood cell transfusion in 4 (3.8%), and radiological embolization in 1 (1%). The most frequent pathological diagnoses were: non-diabetic glomerular diseases (29.8%, including pauci-immune crescentic glomerulonephritis in 9.6%), hypertensive nephropathy (27.9%), acute interstitial nephritis (16.3%), renal involvement of hematological malignancy (8.7%), and acute tubular necrosis (6.7%). After KB, 51 (49%) patients received a specific treatment: corticosteroids (41.3%), cyclophosphamide (6.7%), rituximab (6.7%), bortezomib (3.8%), other chemotherapies (3.8%). Median overall survival was 31 months.

CONCLUSIONS

KB can reveal a diagnosis with therapeutic impact even in very elderly patients. Severe bleeding was not frequent in this cohort, but KB may have not been performed in more vulnerable patients.

Cost-Effectiveness of Targeted Exome Analysis as a Diagnostic Test in Glomerular Diseases

BACKGROUND

Despite the emergence of diagnostic and clinical utility evidence in nephrology, publicly funded access to genomic testing is restricted in most health care systems. To establish genomic sequencing as a clinical test, an evaluation of cost-effectiveness is urgently required.

METHODS

An economic evaluation, informed by a primary clinical study and available clinical evidence and guidelines in nephrology, was performed to evaluate the cost-effectiveness and optimal timing of exome sequencing (ES) in adults and children with suspected monogenic glomerular diseases compared with nongenomic investigations (NGIs). Six diagnostic strategies reflecting current practice and recommended models of care in Australia were modeled: (i) NGIs, (ii) late gene panel followed by ES, (iii) late ES, (iv) early gene panel, (v) early gene panel followed by ES, and (vi) early ES.

RESULTS

ES with targeted analysis achieved a diagnosis in 23 of 63 (36.5%) adults and 10 of 24 (41.6%) children. NGIs were estimated to diagnose 4.0% of children, with an average estimated cost of AU$6120 per child. Integrating ES as a first-line test in children was cost saving, with an incremental cost saving of AU$3230 per additional diagnosis compared with NGIs. In adults, NGIs was estimated to diagnose 8% of patients, with an average estimated cost of AU$1830 per person. In adults, integrating ES early resulted in an incremental cost per additional diagnosis of AU$5460 relative to NGIs.

CONCLUSIONS

Early ES with targeted analysis was effective for diagnosing monogenic kidney disease, with substantial cost savings in children.

A Case of Cast Nephropathy Found as the Cause of Severe Renal Failure

Cast nephropathy is rare kidney disease with slow progression. It is associated with multiple myeloma (MM). In this study, we report a case of cast nephropathy in an 86-year-old woman who was previously independent in her activities of daily living (ADLs). However, she was found to have severe renal impairment after vomiting and a decrease in her ADLs. Blood and urine tests revealed the renal disorder. The patient was immediately treated with hemodiafiltration. IgG, IgA, and IgM levels were decreased by immunoelectrophoresis. A kidney biopsy showed crystals and periodic acid-Schiff stain (PAS)-negative urinary casts in the tubules. Bence Jones protein-lambda type M protein was detected in the urine. The patient was diagnosed with cast nephropathy due to MM. Hemodialysis was continued. The patient's family and the patient did not wish to initiate chemotherapy. The decision was made to follow the patient's progress. In this case, a patient who was originally independent in her ADLs developed severe renal failure with an acute course. This case suggests the importance of differentiating MM based on renal failure, even if the presentation is not typical, as elderly patients may have an atypical presentation of the disease, which can avoid invasive procedures such as renal biopsy.

A Systematic Literature Review of the Epidemiology, Health-Related Quality of Life Impact, and Economic Burden of Immunoglobulin A Nephropathy

Introduction: This systematic literature review analyzed published evidence on IgA nephropathy (IgAN), focusing on US epidemiology, health-related quality of life (HRQoL), and economic burden of illness. Methods: Using Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, Embase®, MEDLINE®, Cochrane, and Econlit (January 2010 to June 2020) were searched, along with relevant congresses (2017-2020). Results: Of 123 epidemiologic studies selected for data extraction, 24 reported IgAN diagnosis rates ranging from 6.3% to 29.7% among adult and pediatric patients undergoing renal biopsy, with all reported US rates <15%. No US studies reported IgAN prevalence. A meta-analysis of US studies calculated an annual incidence of 1.29/100 000 people, translating to an annual US incidence of 4236 adults and children. Relative to Europe, the United States had more patients diagnosed with IgAN in later chronic kidney disease stages. US rates of transition to end-stage renal disease (ESRD) ranged from 12.5% to 23% during 3-3.9 years of observation, rising to 53% during 19 years of observation. Across 8 studies reporting HRQoL, pain and fatigue were the most reported symptoms, and patients consistently ranked kidney function and mortality as the most important treatment outcomes. Patients with glomerulopathy reported worse mental health than healthy controls or hemodialysis patients; proteinuria was significantly associated with poorer HRQoL and depression. Conclusion: While economic evidence in IgAN remains sparse, management of ESRD is a major cost driver. IgAN is a rare disease where disease progression causes increasing patient burden, underscoring the need for therapies that prevent kidney function decline and HRQoL deterioration while reducing mortality.

Biopsy-proven Renal Pathologies: Experience from Multan Institute of Kidney Diseases

In this part of world, nephrology data lack as there is no renal registry, and nephrology is still in its primitive stage. Multan Institute of kidney diseases started tertiary care renal services. We carried out an analysis of our renal biopsies performed here from August 2017 to May 2019. This was carried out to see the spectrum of renal diseases in this area. This is a retrospective analysis of renal biopsies performed at the Multan Institute of Kidney Diseases from August 2017 to May 2019. Renal biopsy was performed using real-time ultrasound. One hundred and seventy-five native renal biopsies were performed during this study period. One hundred and three male (59%) and 72 female (41%) patients underwent renal biopsy. The average age was 36 years, with a range of 16-70 years. Results from our study showed membranous glomerulo- nephritis (36%) as a leading cause of primary glomerular disease in this region. Lupus nephritis (30.3%) was a leading cause in secondary glomerular disease. Reviewing our study and published literature it's pellucid that lupus nephritis is a leading cause of secondary glomerulonephritis worldwide. In terms of primary glomerular disease, spectrum is different globally. This study sets alight to explore membranous nephropathy, which is the leading primary glomerular disease in our studied population.

Epidemiology of biopsy-proven glomerulonephritis in the past 25 years in the North-Eastern area of Romania

PURPOSE

The aim of this retrospective study was: to analyze the epidemiological patterns of the kidney disease based on clinical and histological features in a single-center in the N-E region of Romania, between 2011 and 2019 and to compare the biopsy results with the others periods, as well as the results from other countries.

METHODS

We studied 442 renal biopsies. The indications for renal biopsy were represented by the clinical features: nephrotic syndrome, nephritic syndrome, asymptomatic urinary abnormalities, acute kidney injury, and chronic kidney disease of unknown etiology.

RESULTS

During the past 8 years, the annual incidence of renal biopsies was constant, albeit this incidence remained lower than in other countries. Nephrotic syndrome was the most common indication for renal biopsy (47.6%). Primary glomerulonephritis (GN) was the most common diagnosis in each of the three periods, followed by secondary GN. Vascular nephropathy and TIN were constant as a proportion from the overall biopsies in each of the three periods. The membranoproliferative GN (24.4%) and membranous nephropathy (MN) (21.9%) were the most prevalent primary GN, while lupus nephritis (LN) was the most common secondary glomerular disease in young female patients (7.5%). Compared to 1994-2004 period, we observed a significant decrease of incidence of focal segmental glomerulosclerosis (FSGS) and mesangial proliferative GN, and a significant increases in the frequency of MN.

CONCLUSION

The results of this study show that the GN distribution model was constant in N-E Romania and became similar to that observed in many countries with high socio-economic status.

Understanding glomerular diseases through proteomics

INTRODUCTION

Chronic kidney disease is avery common and complex chronic disease. Uncovering the pathological patterns of CKD on the molecular level of bio-fluids and tissue appears to be both vital and promising for a more favorable outcome. We reviewed recently discovered proteomics biomarkers for CKD to provide new insight into disease pathology.

AREAS COVERED

We review the application of proteome analysis in the context of CKD with various etiologies within the last 5 years. Proteins and peptides associated with CKD as derived from multiple sources (urine, blood and tissue) are reported along with their various biological pathways.

EXPERT OPINION

A systematic and theoretical comprehension of the CKD pathology is essential for its successful management. The underlying complexity of the disease further requires specific conditions for reliable and interpretable results. In this context, clinical proteomics has resulted in first encouraging findings in CKD. A more complete understanding of the biological pathways related to the disease, based on the scope of a holistic proteomic approach, could improve substantially the management of CKD, especially when in conjunction with the current trend of personalized medicine.

Diabetic retinopathy in the Eastern Morocco: Different stage frequencies and associated risk factors

Diabetes is a major cause of morbidity and mortality worldwide. It can affect many organs and, over time, leads to serious complications. Diabetic retinopathy (DR), a specific ocular complication of diabetes, remains the leading cause of vision loss and vision impairment in adults. This work is the first in Eastern Morocco aimed at identifying the different stages of DR and to determine their frequencies and associated risk factors. It is a case-control study conducted from December 2018 to July 2019 at the ophthalmology department of Al-Irfane Clinic (Oujda). Data were obtained from a specific questionnaire involving 244 diabetic patients (122 cases with retinopathy vs 122 controls without retinopathy). All results were analyzed by the EPI-Info software. This study shows a predominance of proliferative diabetic retinopathy (PDR) with 57.4% of cases (uncomplicated proliferative diabetic retinopathy (UPDR): 23.8%; complicated proliferative diabetic retinopathy (CPDR): 33.6%). The non-proliferative diabetic retinopathy (NPDR) represents 42.6% (minimal NPDR: 8.2%; moderate NPDR: 26.2%; severe NPDR: 8.2%). The determinants of DR were insulin therapy, high blood pressure, poor glycemic control and duration of diabetes. Regarding the chronological evolution, retinopathy precedes nephropathy. Diabetic nephropathy (DN) was present in 10.6% of cases especially in patients with PDR. In summary, the frequency of PDR was higher than that of NPDR. DR appears before DN with a high frequency of DN in patients with PDR. Good glycemic control and blood pressure control, as well as early diagnosis are the major preventive measures against DR.

A Systematic Literature Review of the Epidemiology, Health-Related Quality of Life Impact, and Economic Burden of Immunoglobulin A Nephropathy

Introduction: This systematic literature review analyzed published evidence on IgA nephropathy (IgAN), focusing on US epidemiology, health-related quality of life (HRQoL), and economic burden of illness. Methods: Using Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, Embase®, MEDLINE®, Cochrane, and Econlit (January 2010 to June 2020) were searched, along with relevant congresses (2017-2020). Results: Of 123 epidemiologic studies selected for data extraction, 24 reported IgAN diagnosis rates ranging from 6.3% to 29.7% among adult and pediatric patients undergoing renal biopsy, with all reported US rates <15%. No US studies reported IgAN prevalence. A meta-analysis of US studies calculated an annual incidence of 1.29/100 000 people, translating to an annual US incidence of 4236 adults and children. Relative to Europe, the United States had more patients diagnosed with IgAN in later chronic kidney disease stages. US rates of transition to end-stage renal disease (ESRD) ranged from 12.5% to 23% during 3-3.9 years of observation, rising to 53% during 19 years of observation. Across 8 studies reporting HRQoL, pain and fatigue were the most reported symptoms, and patients consistently ranked kidney function and mortality as the most important treatment outcomes. Patients with glomerulopathy reported worse mental health than healthy controls or hemodialysis patients; proteinuria was significantly associated with poorer HRQoL and depression. Conclusion: While economic evidence in IgAN remains sparse, management of ESRD is a major cost driver. IgAN is a rare disease where disease progression causes increasing patient burden, underscoring the need for therapies that prevent kidney function decline and HRQoL deterioration while reducing mortality.

Pattern of kidney diseases in Northern India: an overview through histopathological findings in biopsy-proven cases

Background

A kidney biopsy is being increasingly performed for the diagnosis of renal diseases. It is a reasonably safe procedure that helps not only to reach the correct diagnosis based on histopathological findings but also helps in predicting the clinical course and outcome. The pattern of kidney diseases varies not only in far apart geographical regions but also in the same country. This study was done to evaluate the demographic pattern and spectrum of kidney diseases in renal biopsy-proven cases in an admitted patient of a tertiary care hospital of northern India.

Results

The mean age of patients was 41.3 years ± 18.39 years, and the male-to-female ratio was 1.7:1. The most common indication for biopsy in this study was nephrotic syndrome (40.5%). The primary glomerular disease was most common, accounting for 57.5% of cases. Membranous nephropathy (MN) was the most frequently observed histopathological diagnosis not only in the primary glomerular disease category (22.9%) but of all cases (13.2%) as well. Among secondary cases, diabetic nephropathy was most frequent, constituting 43.4% cases. Interstitial and vascular diseases accounted for 18.8% and 1.8% of total cases, respectively. While minimal change disease (MCD) was the most common diagnosis in < 18-year age group, membranous nephropathy was most common above this age. Regarding the gender factor, membranoproliferative glomerulonephritis had an equal distribution among both genders, while MCD had a female preponderance.

Conclusions

Primary glomerular disease is the predominant kidney disease in northern India with MN being the most common histopathological diagnosis. The spectrum of kidney diseases varied with patient’s age and gender.

Integration of genetic and histopathology data in interpretation of kidney disease

For many years renal biopsy has been the gold standard for diagnosis in many forms of kidney disease. It provides rapid, accurate and clinically useful information in most individuals with kidney disease. However, in recent years, other diagnostic modalities have become available that may provide more detailed and specific diagnostic information in addition to, or instead of, renal biopsy. Genomics is one of these modalities. Previously prohibitively expensive and time consuming, it is now increasingly available and practical in a clinical setting for the diagnosis of inherited kidney disease. Inherited kidney disease is a significant cause of kidney disease, in both the adult and paediatric populations. While individual inherited kidney diseases are rare, together they represent a significant burden of disease. Because of the heterogenicity of inherited kidney disease, diagnosis and management can be a challenge and often multiple diagnostic modalities are needed to arrive at a diagnosis. We present updates in genomic medicine for renal disease, how genetic testing integrates with our knowledge of renal histopathology and how the two modalities may interact to enhance patient care.

Congestive nephropathy: a neglected entity? Proposal for diagnostic criteria and future perspectives

Venous congestion has emerged as an important cause of renal dysfunction in patients with cardiorenal syndrome. However, only limited progress has been made in differentiating this haemodynamic phenotype of renal dysfunction, because of a significant overlap with pre-existing renal impairment due to long-term hypertension, diabetes, and renovascular disease. We propose congestive nephropathy (CN) as this neglected clinical entity. CN is a potentially reversible subtype of renal dysfunction associated with declining renal venous outflow and progressively increasing renal interstitial pressure. Venous congestion may lead to a vicious cycle of hormonal activation, increased intra-abdominal pressure, excessive renal tubular sodium reabsorption, and volume overload, leading to further right ventricular (RV) stress. Ultimately, renal replacement therapy may be required to relieve diuretic-resistant congestion. Effective decongestion could preserve or improve renal function. Congestive acute kidney injury may not be associated with cellular damage, and complete renal function restoration may be a confirmatory diagnostic criterion. In contrast, a persistently low renal perfusion pressure might induce renal dysfunction and histopathological lesions with time. Thus, urinary markers may differ. CN is mostly seen in biventricular heart failure but may also occur secondary to pulmonary arterial hypertension and elevated intra-abdominal pressure. An increase in central venous pressure to >6 mmHg is associated with a steep decrease in glomerular filtration rate. However, the central venous pressure range that can provide an optimal balance of RV and renal function remains to be determined. We propose criteria to identify cardiorenal syndrome subgroups likely to benefit from decongestive or pulmonary hypertension-specific therapies and suggest areas for future research.

Shear wave elastography accurately detects chronic changes in renal histopathology

AIM

Renal biopsy is the gold standard for the histological characterization of chronic kidney disease (CKD), of which renal fibrosis is a dominant component, affecting its stiffness. The aim of this study was to investigate the correlation between kidney stiffness obtained by shear wave elastography (SWE) and renal histological fibrosis.

METHODS

Shear wave elastography assessments were performed in 75 CKD patients who underwent renal biopsy. The SWE-derived estimates of the tissue Young's modulus (YM), given as kilopascals (kPa), were measured. YM was correlated to patients' renal histological scores, broadly categorized into glomerular, tubulointerstitial and vascular scores.

RESULTS

Young's modulus correlates significantly with tubulointerstitial score (ρ = 0.442, P < .001) and glomerular score (ρ = 0.375, P = .001). Patients with no glomerular sclerosis showed lower mean YM measurements compared to those with glomerular sclerosis. The mean YM increased as the percentage of interstitial fibrosis and tubular atrophy increased. The area under the receiver operating characteristic curve (ROC) for SWE in differentiating between mildly and moderately impaired kidneys was 0.702.

CONCLUSION

Shear wave elastography accurately detects chronic renal damage resulting from glomerular sclerosis, interstitial fibrosis and tubular atrophy, using the optimal cut-off YM value of ≥5.81 kPa.

Current findings of kidney biopsy including nephropathy associated with hypertension and diabetes mellitus in Korea

BACKGROUND/AIMS

This study aimed to investigate long-term temporal trends and outcomes of biopsy-proven kidney diseases in a multicenter kidney biopsy cohort, focusing on hypertension and diabetes, the leading causes of end-stage kidney disease (ESKD).

METHODS

The study included a total of 21,426 patients who underwent kidney biopsy from 1979 to 2018 in 18 hospitals in Korea. We selected subgroups of adults with diabetes (n = 2,813) or clinically presumed hypertensive nephrosclerosis (HT-N, n = 2,917). Clinical, demographic, and laboratory data were collected in conjunction with pathologic findings. The prevalence of pathologically confirmed kidney diseases over time and their associations with clinical outcomes were evaluated.

RESULTS

The prevalence of biopsy-proven diabetic nephropathy (DN) has increased significantly from 2.5% to 6.0% in the total cohort in the recent 30 years with an increase in the prevalence of diabetes. Approximately 68% of total diabetic patients had non-diabetic renal disease (NDRD); the proportion was retained since 2000s. DN showed a significantly higher risk of ESKD than NDRD (hazard ratio [HR], 1.59; 95% confidence interval [CI], 1.35 to 1.88). The prevalence of biopsy-proven HT-N remained < 2% in the total cohort for several decades. There was no difference in risks of ESKD between patients with or without biopsy-proven HT-N (HR, 0.93; 95% CI, 0.54 to 1.59).

CONCLUSION

In recent decades, the prevalence of diabetes and DN has significantly increased in the kidney biopsy cohort, showing an increased risk of ESKD. Despite the large numbers of patients meeting the clinical criteria of HT-N, most of those were diagnosed with pathologic diagnoses other than HT-N.