Renal biopsy practice: What is the gold standard?

Development and validation of multi-center serum creatinine-based models for noninvasive prediction of kidney fibrosis in chronic kidney disease

OBJECTIVE

Kidney fibrosis is a key pathological feature in the progression of chronic kidney disease (CKD), traditionally diagnosed through invasive kidney biopsy. This study aimed to develop and validate a noninvasive, multi-center predictive model incorporating machine learning (ML) for assessing kidney fibrosis severity using biochemical markers.

METHODS

This multi-center retrospective study included 598 patients with kidney fibrosis from four hospitals. A training cohort of 360 patients from Shanghai Tongji Hospital was used to develop a predictive nomogram and ML model, with fibrosis severity classified as mild or moderate-to-severe based on Banff scores. Logistic regression identified key predictors, which were incorporated into a nomogram and ML model. An external validation cohort of 238 patients from three additional hospitals was used for model evaluation.

RESULTS

Serum creatinine (Scr), estimated glomerular filtration rate (eGFR), parathyroid hormone (PTH), brain natriuretic peptide (BNP), and sex were identified as independent predictors of kidney fibrosis severity. The nomogram demonstrated superior discriminative ability in the training cohort (AUC: 0.89, 95% CI: 0.85-0.92) compared to eGFR (AUC: 0.83, 95% CI: 0.78-0.87) and Scr (AUC: 0.87, 95% CI: 0.83-0.91). Among ML models, the Random Forest (RF) model achieved the highest AUC (0.98). In external validation, the nomogram and RF models maintained robust performance with AUCs of 0.86 and 0.79, respectively.

CONCLUSION

This study presents a validated, noninvasive, multi-center Scr-based machine learning model for assessing kidney fibrosis severity in CKD. The integration of a clinical nomogram and ML approach offers a novel, practical alternative to biopsy for dynamic fibrosis evaluation.

Advances in kidney biopsy lesion assessment through dense instance segmentation

Renal biopsies are the gold standard for the diagnosis of kidney diseases. Lesion scores made by renal pathologists are semi-quantitative and exhibit high inter-observer variability. Automating lesion classification within segmented anatomical structures can provide decision support in quantification analysis, thereby reducing inter-observer variability. Nevertheless, classifying lesions in regions-of-interest (ROIs) is clinically challenging due to (a) a large amount of densely packed anatomical objects, (b) class imbalance across different compartments (at least 3), (c) significant variation in size and shape of anatomical objects and (d) the presence of multi-label lesions per anatomical structure. Existing models cannot address these complexities in an efficient and generic manner. This paper presents an analysis for a generalized solution to datasets from various sources (pathology departments) with different types of lesions. Our approach utilizes two sub-networks: dense instance segmentation and lesion classification. We introduce DiffRegFormer, an end-to-end dense instance segmentation sub-network designed for multi-class, multi-scale objects within ROIs. Combining diffusion models, transformers, and RCNNs, DiffRegFormer is a computational-friendly framework that can efficiently recognize over 500 objects across three anatomical classes, i.e., glomeruli, tubuli, and arteries, within ROIs. In a dataset of 303 ROIs from 148 Jones' silver-stained renal Whole Slide Images (WSIs), our approach outperforms previous methods, achieving an Average Precision of 52.1% (detection) and 46.8% (segmentation). Moreover, our lesion classification sub-network achieves 89.2% precision and 64.6% recall on 21889 object patches out of the 303 ROIs. Lastly, our model demonstrates direct domain transfer to PAS-stained renal WSIs without fine-tuning.

Technical and Institutional Factors Affecting Specimen Adequacy and Complications in Ultrasound-guided Kidney Biopsy: A Retrospective Cohort Study

Background

Percutaneous ultrasound-guided kidney biopsy is a critical diagnostic tool with a higher rate of complications than most other biopsies. Our prior research identified technical factors that might improve outcomes.

Objective

The objective was to measure the impact of these technical and institutional interventions on specimen adequacy and complication rates in kidney biopsies.

Design

This is a retrospective cohort study comparing outcomes before and after intervention implementation.

Setting

Two hospitals within a single health region in Saskatchewan serving a population of approximately 1 million.

Patients

All adult percutaneous ultrasound-guided kidney biopsies performed on adult patients between 2012 to 2016 (n = 242, pre-implementation) and 2017 to 2021 (n = 338, post-implementation). Both native and transplant biopsies were included, while patients under 18, open biopsies, and biopsies of kidney masses were excluded.

Measurements

Primary outcomes included specimen adequacy and biopsy complications (hematoma, hemoglobin drop, infection, and arteriovenous fistula formation).

Methods

Technical recommendations included introducing the biopsy needle at a 60° angle, targeting a pole, and avoiding the vascular medulla. Institutional recommendations included microscopic screening for all biopsies, limiting the number of radiologists performing procedures, using a checklist, and restricting computed tomography (CT)-guided biopsies to exceptional cases. Multivariate regression analysis assessed biopsy outcomes before and after the recommendations, controlling for known confounders while at the same time refining factors associated with fewer complications and greater diagnostic yield.

Results

The rate of non-diagnostic specimens decreased from 10.3% to 4.4% (P = .005), and complications decreased from 35.5% to 14.2% (P < .0001). Two or three passes yielded excellent diagnostic success, while 4 passes increased the risk of a complication. Multivariate analysis, after accounting for the collinearity of certain technical factors revealed that medulla avoidance and biopsies done after the implementation of the 2016 recommendations significantly reduced the risk of complications (odds ratio [OR] = 0.37, P < .001) and non-diagnostic biopsies (OR = 0.31, P = .002).

Limitations

Retrospective design and novelty bias may be a cause of bias in this study. Because the institutional recommendations were followed for all biopsies, it was not possible to distinguish which recommendation was most associated with the improvements. Because our study was done in a single health region, it is not clear if they are generalizable to other programs.

Conclusions

The technical and institutional interventions implemented significantly improved specimen adequacy and reduced complication rates in ultrasound-guided kidney biopsies. We have added to these recommendations in that we have refined the requirement for angling the biopsy needle for ease of use and suggest limiting the number of passes to 2 or 3 whenever possible.

Urinary V-Set Ig Domain-Containing Protein 4 and Immune Complexes for Tracking Lupus Nephritis and Renal Pathology

OBJECTIVE

This study aims to investigate whether V-set Ig domain-containing protein 4 (VSIG4; also known as complement receptor of the Ig superfamily [CRIg]) forms immune complexes (ICxs) with IgG and complement component 3 (C3) in the kidneys of patients with lupus nephritis (LN) and to assess the potential of urinary VSIG4 and VSIG4-ICx as noninvasive biomarkers of LN.

METHODS

Immunofluorescent staining was employed to detect the deposition of VSIG4 (CRIg), IgG, and C3 in kidney tissue. Urine samples from 102 patients with LN, 51 healthy controls (HCs), and 13 patients with chronic kidney disease (CKD) were analyzed via enzyme-linked immunosorbent assay for VSIG4-ICx and free-form VSIG4.

RESULTS

Immunofluorescence costaining demonstrated the colocalization of VSIG4, IgG, and C3 in the kidneys of those with LN and elevated VSIG4 protein expression in the glomeruli regions in LN. Compared with HCs and those with CKD, patients with LN exhibited significantly elevated levels of urinary VSIG4 in both free form and ICx. Urinary VSIG4-ICx correlated with clinical parameters, including the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) (R = 0.55, P < 0.0001), renal SLEDAI (R = 0.52, P < 0.0001), estimated glomerular filtration rate (-0.5, P < 0.001), activity index (R = 0.25, P < 0.05), chronicity index (R = 0.32, P < 0.05), complement C3 (R = -0.33, P < 0.05), and complement C4 (R = -0.31, P < 0.05). The strong association of the urinary VSIG4-ICx with disease activity metrics and histopathologic evidence underscores its potential for clinical utility in diagnosing and monitoring LN.

CONCLUSION

VSIG4-ICx shows promise as a novel urine biomarker for LN, with potential utility for diagnosis and disease monitoring.

Shear-Wave Elastography Improves Diagnostic Accuracy in Chronic Kidney Disease Compared to Conventional Ultrasound

PURPOSE

Non-invasive tests are increasingly demanded for diagnosing and prognostication of chronic kidney disease (CKD). Shear-wave elastography (SWE), an emerging technique for measuring tissue stiffness, shows promise for distinguishing between individuals with different stages of renal fibrosis. This study aimed to compare the diagnostic accuracy of two-dimensional SWE (2D-SWE) and conventional ultrasound for detecting CKD, employing renal biopsy as the gold standard.

METHODS

From May 2020 to October 2023, this prospective study included 30 healthy volunteers and 169 patients with CKD who had undergone 2D-SWE and conventional ultrasound of both kidneys. Cortical and medullary stiffness, cortical pixel intensity, renal length, parenchymal and cortical thickness, interlobar artery peak systolic velocity, end-diastolic velocity (EDV), and resistive index were measured. The diagnostic accuracy of 2D-SWE and conventional ultrasound was compared using the receiver operating characteristic curve (ROC) and Delong test.

RESULTS

For diagnosing CKD, the area under the ROC (AUC) of cortical stiffness (0.96 [95% CI, 0.93, 0.99]) was significantly higher than that of all conventional ultrasound parameters, including EDV (0.78 [95% CI, 0.71, 0.86]) and cortical thickness (0.74 [95% CI, 0.67, 0.80]). The sensitivity of cortical stiffness (91%) was significantly higher than that of EDV (68%) and cortical thickness (53%). No significant difference was found in the specificity of cortical stiffness (96%) compared to that of EDV (79%) and cortical thickness (100%).

CONCLUSION

Two-dimensional SWE showed higher diagnostic accuracy than that of conventional ultrasound for detecting CKD.

Diffusion tensor MRI is sensitive to fibrotic injury in a mouse model of oxalate-induced chronic kidney disease

Chronic kidney disease (CKD) is characterized by inflammation and fibrosis in the kidney. Renal biopsies and estimated glomerular filtration rate (eGFR) remain the standard of care, but these endpoints have limitations in detecting the stage, progression, and spatial distribution of fibrotic pathology in the kidney. MRI diffusion tensor imaging (DTI) has emerged as a promising noninvasive technology to evaluate renal fibrosis in vivo both in clinical and preclinical studies. However, these imaging studies have not systematically identified fibrosis particularly deeper in the kidney where biopsy sampling is limited, or completed an extensive analysis of whole organ histology, blood biomarkers, and gene expression to evaluate the relative strengths and weaknesses of MRI for evaluating renal fibrosis. In this study, we performed DTI in the sodium oxalate mouse model of CKD. The DTI parameters fractional anisotropy, apparent diffusion coefficient, and axial diffusivity were compared between the control and oxalate groups with region of interest (ROI) analysis to determine changes in the cortex and medulla. In addition, voxel-based analysis (VBA) was implemented to systematically identify local regions of injury over the whole kidney. DTI parameters were found to be significantly different in the medulla by both ROI analysis and VBA, which also spatially matched with collagen III immunohistochemistry (IHC). The DTI parameters in this medullary region exhibited moderate to strong correlations with histology, blood biomarkers, hydroxyproline, and gene expression. Our results thus highlight the sensitivity of DTI to the heterogeneity of renal fibrosis and importance of whole kidney noninvasive imaging.NEW & NOTEWORTHY Chronic kidney disease (CKD) can be characterized by inflammation and fibrosis of the kidney. Although standard of care methods have been limited in scope, safety, and spatial distribution, MRI diffusion tensor imaging (DTI) has emerged as a promising noninvasive technology to evaluate renal fibrosis in vivo. In this study, we performed DTI in an oxalate mouse model of CKD to systematically identify local kidney injury. DTI parameters strongly correlated with histology, blood biomarkers, hydroxyproline, and gene expression.

Reduction of patients' bed rest time after percutaneous renal biopsy evaluated by the Nursing Outcomes Classification: Randomized clinical trial

PURPOSE

To evaluate the reduction of patients' bed rest time after percutaneous renal biopsy (PRB) from 24 to 8 h using the Nursing Outcomes Classification (NOC).

METHODS

This was a randomized clinical trial registered with Clinical Trials number NCT04629235. The sample comprised 16 patients in the intervention group and 18 in the control group. In the intervention group, the rest time was modified to 8 h, and afterward, the patients were released to ambulate, whereas the control patients remained at absolute rest for 24 h after PRB according to institutional protocol. All patients were observed for 24 h and evaluated at five time points with the outcomes and indicators of the NOC: before the biopsy, immediately after, at the 8th hour, at the 12th hour, and at the 24th hour after the procedure.

RESULTS

In the 170 evaluations performed, statistically significant differences were identified in the outcome Comfort status: physical and the indicators "physical well-being and comfortable position." None of the complications were related to reduced bed rest time.

CONCLUSIONS

Reducing patients' bed rest time from 24 to 8 h did not increase complications from PRB, and using the NOC provided a standardized and reliable assessment.

IMPLICATIONS FOR NURSING PRACTICE

Important evidence was identified for patient care after PRB, demonstrating the positive impact on patient comfort and the possibility of reducing costs to the institution and the workload of the multidisciplinary team. In addition, these findings may contribute to strengthening the use of NOC in clinical practice, teaching, and research.

Role of Desmopressin Acetate before Percutaneous Ultrasound-Guided Kidney Biopsy in Patients with Kidney Dysfunction

Background

The most common complication of percutaneous kidney biopsy is bleeding, which can be seen in up to one-third of cases. The aim of this study was to evaluate the effect of prebiopsy administration of intranasal desmopressin acetate in reducing the incidence of biopsy-related bleeding complications.

Materials and Methods

This was a prospective randomized double-blind pilot study conducted at our center from January 2021 to September 2022. Consecutive adult patients who underwent native percutaneous kidney biopsy with an estimated glomerular filtration rate (eGFR) ≤45 ml/min/1.73 m2 were randomized into a placebo (saline intranasal spray) group versus intranasal desmopressin group. The bleeding complications were compared between the two groups.

Results

A total of 80 patients who underwent kidney biopsy at our center from January 2021 to September 2022 with eGFR ≤45 ml/min/1.73 m2 were included (40 patients in desmopressin group and 40 patients in non-desmopressin group) in the study. The mean age of the patients was 44 ± 12 years with a mean eGFR of 20.82 ± 12.64 ml/min/1.73 m2. Intranasal desmopressin administration before kidney biopsy was associated with a significantly higher number of minor bleeding complications (P = 0.02) and no significant reduction in major complications (P = 0.15) when compared with a group that did not receive desmopressin. Other complications like hypotension, flushing, and vasovagal syncope were not statistically significantly associated with the use of desmopressin.

Conclusion

Our study did not find any utility of prophylactic desmopressin use before kidney biopsy in patients with kidney dysfunction.

Fibrosis in Chronic Kidney Disease: Pathophysiology and Therapeutic Targets

Chronic kidney disease (CKD) is a slowly progressive condition characterized by decreased kidney function, tubular injury, oxidative stress, and inflammation. CKD is a leading global health burden that is asymptomatic in early stages but can ultimately cause kidney failure. Its etiology is complex and involves dysregulated signaling pathways that lead to fibrosis. Transforming growth factor (TGF)-β is a central mediator in promoting transdifferentiation of polarized renal tubular epithelial cells into mesenchymal cells, resulting in irreversible kidney injury. While current therapies are limited, the search for more effective diagnostic and treatment modalities is intensive. Although biopsy with histology is the most accurate method of diagnosis and staging, imaging techniques such as diffusion-weighted magnetic resonance imaging and shear wave elastography ultrasound are less invasive ways to stage fibrosis. Current therapies such as renin-angiotensin blockers, mineralocorticoid receptor antagonists, and sodium/glucose cotransporter 2 inhibitors aim to delay progression. Newer antifibrotic agents that suppress the downstream inflammatory mediators involved in the fibrotic process are in clinical trials, and potential therapeutic targets that interfere with TGF-β signaling are being explored. Small interfering RNAs and stem cell-based therapeutics are also being evaluated. Further research and clinical studies are necessary in order to avoid dialysis and kidney transplantation.

Urinary peptidomic liquid biopsy for non-invasive differential diagnosis of chronic kidney disease

BACKGROUND AND HYPOTHESIS

Specific urinary peptides hold information on disease pathophysiology, which, in combination with artificial intelligence, could enable non-invasive assessment of chronic kidney disease (CKD) aetiology. Existing approaches are generally specific for the diagnosis of single aetiologies. We present the development of models able to simultaneously distinguish and spatially visualize multiple CKD aetiologies.

METHODS

The urinary peptide data of 1850 healthy control (HC) and CKD [diabetic kidney disease (DKD), immunoglobulin A nephropathy (IgAN) and vasculitis] participants were extracted from the Human Urinary Proteome Database. Uniform manifold approximation and projection (UMAP) coupled to a support vector machine algorithm was used to generate multi-peptide models to perform binary (DKD, HC) and multiclass (DKD, HC, IgAN, vasculitis) classifications. This pipeline was compared with the current state-of-the-art single-aetiology CKD urinary peptide models.

RESULTS

In an independent test set, the developed models achieved 90.35% and 70.13% overall predictive accuracies, respectively, for the binary and the multiclass classifications. Omitting the UMAP step led to improved predictive accuracies (96.14% and 85.06%, respectively). As expected, the HC class was distinguished with the highest accuracy. The different classes displayed a tendency to form distinct clusters in the 3D space based on their disease state.

CONCLUSION

Urinary peptide data present an effective basis for CKD aetiology differentiation using machine learning models. Although adding the UMAP step to the models did not improve prediction accuracy, it may provide a unique visualization advantage. Additional studies are warranted to further validate the pipeline's clinical potential as well as to expand it to other CKD aetiologies and also other diseases.

Amide Proton Transfer-Weighted Magnetic Resonance Imaging for Application in Renal Fibrosis: A Radiological-Pathological-Based Analysis

INTRODUCTION

Renal fibrosis (RF), being the most important pathological change in the progression of CKD, is currently assessed by the evaluation of a biopsy. This present study aimed to apply a novel functional MRI (fMRI) protocol named amide proton transfer (APT) weighting to evaluate RF noninvasively.

METHODS

Male Sprague-Dawley (SD) rats were initially subjected to bilateral kidney ischemia/reperfusion injury (IRI), unilateral ureteral obstruction, and sham operation, respectively. All rats underwent APT mapping on the 7th and 14th days after operation. Besides, 26 patients underwent renal biopsy at the Nephrology Department of Shanghai Tongji Hospital between July 2022 and May 2023. Patients underwent APT and apparent diffusion coefficient (ADC) mappings within 1 week before biopsy. MRI results of both patients and rats were calculated by comparing with gold standard histology for fibrosis assessment.

RESULTS

In animal models, the cortical APT (cAPT) and medullary APT (mAPT) values were positively correlated with the degree of RF. Compared to the sham group, IRI group showed significantly increased cAPT and mAPT values on the 7th and 14th days after surgery, but no group differences were found in ADC values. Similar results were found in human patients. Cortical/medullary APT values were significantly increased in patients with moderate-to-severe fibrosis than in patients with mild fibrosis. ROC curve analysis indicated that APT value displayed a better diagnostic value for RF. Furthermore, combination of cADC and cAPT improved fibrosis detection by imaging variables alone (p < 0.1).

CONCLUSION

APT values had better diagnostic capability at early stage of RF compared to ADC values, and the addition of APT imaging to conventional ADC will significantly improve the diagnostic performance for predicting kidney fibrosis.

Clinical Characteristics and Outcomes of Drug-Induced Acute Kidney Injury Cases

Introduction

Drug-induced acute kidney injury (DI-AKI) is a frequent adverse event. The identification of DI-AKI is challenged by competing etiologies, clinical heterogeneity among patients, and a lack of accurate diagnostic tools. Our research aims to describe the clinical characteristics and predictive variables of DI-AKI.

Methods

We analyzed data from the Drug-Induced Renal Injury Consortium (DIRECT) study (NCT02159209), an international, multicenter, observational cohort study of enriched clinically adjudicated DI-AKI cases. Cases met the primary inclusion criteria if the patient was exposed to at least 1 nephrotoxic drug for a minimum of 24 hours prior to AKI onset. Cases were clinically adjudicated, and inter-rater reliability (IRR) was measured using Krippendorff's alpha. Variables associated with DI-AKI were identified using L1 regularized multivariable logistic regression. Model performance was assessed using the area under the receiver operating characteristic curve (ROC AUC).

Results

A total of 314 AKI cases met the eligibility criteria for this analysis, and 271 (86%) cases were adjudicated as DI-AKI. The majority of the AKI cases were recruited from the United States (68%). The most frequent causal nephrotoxic drugs were vancomycin (48.7%), nonsteroidal antiinflammatory drugs (18.2%), and piperacillin/tazobactam (17.8%). The IRR for DI-AKI adjudication was 0.309. The multivariable model identified age, vascular capacity, hyperglycemia, infections, pyuria, serum creatinine (SCr) trends, and contrast media as significant predictors of DI-AKI with good performance (ROC AUC 0.86).

Conclusion

The identification of DI-AKI is challenging even with comprehensive adjudication by experienced nephrologists. Our analysis identified key clinical characteristics and outcomes of DI-AKI compared to other AKI etiologies.

Current progress in artificial intelligence-assisted medical image analysis for chronic kidney disease: A literature review

Chronic kidney disease (CKD) causes irreversible damage to kidney structure and function. Arising from various etiologies, risk factors for CKD include hypertension and diabetes. With a progressively increasing global prevalence, CKD is an important public health problem worldwide. Medical imaging has become an important diagnostic tool for CKD through the non-invasive identification of macroscopic renal structural abnormalities. Artificial intelligence (AI)-assisted medical imaging techniques aid clinicians in the analysis of characteristics that cannot be easily discriminated by the naked eye, providing valuable information for the identification and management of CKD. Recent studies have demonstrated the effectiveness of AI-assisted medical image analysis as a clinical support tool using radiomics- and deep learning-based AI algorithms for improving the early detection, pathological assessment, and prognostic evaluation of various forms of CKD, including autosomal dominant polycystic kidney disease. Herein, we provide an overview of the potential roles of AI-assisted medical image analysis for the diagnosis and management of CKD.

The Changing Role of Renal Mass Biopsy

The incidence and prevalence of small renal masses (SRMs) continues to rise and with increased detection comes increases in surgical management, although the probability of an SRM being benign is upward of 30%. An extirpative treatment first diagnose-later strategy persists and clinical tools for risk stratification such as renal mass biopsy remain severely underutilized. The overtreatment of SRMs has multiple detrimental effects including surgical complications, psychosocial stress, financial loss, and reduced renal function leading to downstream effects such as the need for dialysis and cardiovascular disease.

Effects of Aspirin on Kidney Biopsy Bleeding Complications: A Systematic Review and Meta-Analysis (PROSPERO 2021 CRD42021261005)

Postprocedural bleeding is the main complication of percutaneous kidney biopsy (PKB). Therefore, aspirin is routinely withheld in patients undergoing PKB to reduce the bleeding risk. The authors aimed to examine the association between aspirin use and bleeding during PKB. This systematic review and meta-analysis was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The article search was performed on MEDLINE and Scopus using queries specific to each database. Article inclusion was limited to primary studies. The meta-analysis compared the risk of major bleeding events between the aspirin-exposed versus nonexposed group. Pooled effect estimate was examined using random effects presented as odds ratio with 95% confidence intervals. Heterogeneity was assessed through Cochrane I 2 test statistics. Sensitivity and subgroup analyses were also performed according to kidney type. Ten studies were included in the review and four studies were included in the meta-analysis, reviewing a total of 34,067 PKBs. Definitions for significant aspirin exposure were inconsistent between studies, limiting comparisons. Studies with broader definitions for aspirin exposure mostly showed no correlation between aspirin use and postbiopsy bleeding. Studies with strict definitions for aspirin exposure found an increased risk of hemorrhagic events in the aspirin-exposed group. No significant differences were found between the aspirin-exposed and comparison groups regarding major bleeding events (odds ratio 1.72; 95% confidence interval 0.50 to 5.89, I 2 =84%). High-quality evidence on the effect of aspirin on the bleeding risk is limited. Our meta-analysis did not show a significantly increased risk of major bleeding complications in aspirin-exposed patients. Further studies are needed to define a more comprehensive approach for clinical practice.

Serum cystatin C and βeta-2 microglobulin as potential biomarkers in children with lupus nephritis

Objectives: In this study, we aimed to assess serum levels of Cystatin C (Cys C) and beta-2 microglobulin (β2M) in juvenile systemic lupus erythematosus (JSLE) patients and to investigate their role as potential biomarkers of lupus nephritis (LN) and overall disease activity.

Patients and methods: Between December 2018 and November 2019, a total of 40 patients with JSLE (11 males, 29 females; mean age: 12.6±2.5 years; range, 7.5 to 16 years) and 40 age- and sex-matched controls (10 males, 30 females; mean age: 12.3±2.4 years; range, 7 to 16 years) were included in this study. Serum (s) Cys C and β2M levels were compared between the groups. The SLE Disease Activity Index (SLEDAI-2K), the renal SLEDAI (rSLEDAI), and the Renal Damage Index were used.

Results: JSLE patients had significantly elevated mean sCyc C and sβ2M levels (1.4±0.8 mg/mL and 2.8±0.9 mg/mL, respectively) compared to the controls (0.6±0.1 mg/mL and 2.0±0.2 mg/mL, respectively; p<0.00). The mean sCys C and sβ2M levels were significantly higher in the LN group, compared to non-LN patients (1.8±0.7 mg/mL and 3.1±1.0 mg/mL, respectively vs. 0.8±0.3 mg/mL and 2.4±0.6 mg/mL, respectively; p=0.002 and p=0.02, respectively). The sCys C levels had significant positive correlations with erythrocyte sedimentation rate (r=0.3, p=0.05), serum creatinine (r=0.41, p= 0.007), 24-h urinary protein (r=0.58, p<0.001), anti-double stranded deoxyribonucleic acid antibodies titers (r=0.55, p=0.002), extra-renal SLEDAI scores (r=0.36, p=0.04), rSLEDAI (r=0.46, p=0.002), and renal class (r=0.7, p=0.0001). Serum β2M levels were significantly negatively correlated with complement 4 levels (r=-0.31, p=0.04) and significantly positively correlated with extra-renal SLEDAI scores (r=0.3, p=0.05).

Conclusion: These findings confirm that sCys C and sβ2M levels are increased in JSLE patients in association with the overall active disease. However, sCys C level may act as a promising non-invasive biomarker for predicting kidney disease activity and biopsy classes in children with JSLE.

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.

Prevalence of non-diabetic kidney disease and inability of clinical predictors to differentiate it from diabetic kidney disease: results from a prospectively performed renal biopsy study

INTRODUCTION

Renal involvement in type 2 diabetes mellitus (T2DM) may be due to diabetes (diabetic kidney disease (DKD)), causes other than diabetes (non-diabetic kidney disease (NDKD)) or overlap of DKD and NDKD (mixed kidney disease group). Prevalence of NDKD and predictive value of clinical or biochemical indicators have been explored in retrospective cohorts with preselection biases warranting the need for prospectively conducted unbiased renal biopsy study.

RESEARCH DESIGN AND METHODS

Consecutive subjects aged >18 years with T2DM and renal involvement with estimated glomerular filtration rate of 30-60 mL/min/m² and/or albumin:creatinine ratio of >300 mg/g were offered renal biopsy. Prevalence of DKD, NDKD and mixed kidney disease was documented. Clinical/laboratory parameters of subjects were recorded and compared between groups and were tested for ability to predict histopathological diagnosis.

RESULTS

We screened 6247 subjects with T2DM of which 869 fulfilled inclusion criteria for biopsy. Of the 869 subjects, biopsy was feasible in 818 subjects. Out of 818, we recruited first 110 subjects who agreed to undergo renal biopsy. Among those 110 subjects, 73 (66.4%) had DKD; 20 (18.2 %) had NDKD; and 17 (15.4 %) had mixed kidney disease. Subjects with NDKD as compared with DKD had shorter duration of diabetes (p<0.001), absence of retinopathy (p<0.001) and absence of neuropathy (p<0.001). Logistic regression revealed that only presence of retinopathy and duration of diabetes were statistically significant to predict histopathological diagnosis of DKD. 30% of DKD did not have retinopathy, thereby limiting the utility of the same as a discriminator. Use of traditional indicators of biopsy would have indicated a need for renal biopsy in 87.2% of subjects, though 64.5% of the subjects had DKD, who would not have benefitted from biopsy.

CONCLUSION

NDKD and mixed kidney disease in T2DM with renal involvement are very common and traditionally used parameters to select biopsies are of limited value in clinical decision making.

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.

Predictors of perirenal haematoma post-percutaneous ultrasound-guided renal biopsy

Objective

To perform a prospective study to determine the risk factors associated with perirenal haematoma development after percutaneous renal biopsy (PRB).

Methods

This multivariate prospective study collected demographic and clinical data from all consecutive adult patients that underwent real-time ultrasound-guided PRB of native kidneys. All biopsies were performed by two well-trained ultrasound physicians using 16G biopsy needles. Routine renal ultrasounds were performed within 12–24 h after biopsies in order to observe post-biopsy perirenal haematoma formation. Patients were stratified based on the occurrence of post-biopsy haematoma development.

Results

This prospective study enrolled 218 patients and stratified them into a haematoma group (n = 126) and a non-haematoma group (n = 92). Binary logistic regression analysis identified female patients (odds ratio [OR] 1.990; 95% confidence interval [CI] 1.125, 3.521), patients with a body mass index (BMI) ≥28 kg/m² (OR 2.660; 95% CI 1.097, 6.449) and patients with immediate post-biopsy active bleeding (IPAB) (OR 2.572; 95% CI 1.422, 4.655) as being more likely to have perirenal haematoma after real-time ultrasound guided PRB of native kidneys.

Conclusion

Female sex, a BMI ≥28 kg/m² and IPAB were risk factors for perirenal haematoma after real-time ultrasound-guided PRB of native kidneys.

Artificial Intelligence Assessment of Renal Scarring (AIRS Study)

Background

The goal of the Artificial Intelligence in Renal Scarring (AIRS) study is to develop machine learning tools for noninvasive quantification of kidney fibrosis from imaging scans.

Methods

We conducted a retrospective analysis of patients who had one or more abdominal computed tomography (CT) scans within 6 months of a kidney biopsy. The final cohort encompassed 152 CT scans from 92 patients, which included images of 300 native kidneys and 76 transplant kidneys. Two different convolutional neural networks (slice-level and voxel-level classifiers) were tested to differentiate severe versus mild/moderate kidney fibrosis (≥50% versus <50%). Interstitial fibrosis and tubular atrophy scores from kidney biopsy reports were used as ground-truth.

Results

The two machine learning models demonstrated similar positive predictive value (0.886 versus 0.935) and accuracy (0.831 versus 0.879).

Conclusions

In summary, machine learning algorithms are a promising noninvasive diagnostic tool to quantify kidney fibrosis from CT scans. The clinical utility of these prediction tools, in terms of avoiding renal biopsy and associated bleeding risks in patients with severe fibrosis, remains to be validated in prospective clinical trials.

Non-invasive assessment of exfoliated kidney cells extracted from urine using multispectral autofluorescence features

Optimally preserved urinary exfoliated renal proximal tubule cells were assessed by multispectral imaging of cell autofluorescence. We demonstrated different multispectral autofluorescence signals in such cells extracted from the urine of patients with healthy or diseased kidneys. Using up to 10 features, we were able to differentiate cells from individuals with heathy kidneys and impaired renal function (indicated by estimated glomerular filtration rate (eGFR) values) with the receiver operating characteristic area under the curve (AUC) of 0.99. Using the same method, we were also able to discriminate such urine cells from patients with and without renal fibrosis on biopsy, where significant differences in multispectral autofluorescence signals (AUC = 0.90) were demonstrated between healthy and diseased patients (p < 0.05). These findings show that multispectral assessment of the cell autofluorescence in urine exfoliated proximal tubule kidney cells has the potential to be developed as a sensitive, non-invasive diagnostic method for CKD.

Role of Serum Uromodulin in the Early Diagnosis of Chronic Kidney Disease

Background: The diagnosis of chronic kidney disease (CKD) is usually delayed, when significant functional renal impairment has already occurred. The diagnosis is complex and clinical and laboratory investigations play a crucial role. There are well-established markers of CKD – serum creatinine and cystatin C. However, the search for new reliable biomarkers that aid in the assessment of kidney function and predict the evolution of the disease is still in progress.

Objective: To investigate the role of serum uromodulin (sUmod) as a marker for early diagnosis of renal impairment in patients with CKD.

Materials and Methods: We investigated 70 patients, 28 male and 42 female, mean age 56.53 ± 11.753, with CKD in a prospective observational study. All patients were admitted to the Clinic of Nephrology at the “St. Ivan Rilski” University Hospital between April and November 2019. After obtaining written informed consent, laboratory blood and urine tests, abdominal ultrasound and sUmod investigations were performed in all patients.

Results: Plasma uromodulin levels showed decrease with the increasing of the severity of renal impairment. sUmod displayed inverse correlation with serum creatinine (r = -0.467, p < 0.0001), cystatin C (r = -0.430, p < 0.0001) and urea (r = -0.495, p < 0.0001) and a positive correlation with eGFR (r = 0.628, p < 0.0001).

Conclusion: The results of our study show that sUmod levels significantly correlate with all established laboratory parameters used for the evaluation of renal impairment. It can be used as a potential early biomarker for CKD diagnosis.

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

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

Vitamin C and kidney transplantation: Nutritional status, potential efficacy, safety, and interactions

BACKGROUND AND AIM

There are several observational and interventional studies regarding the advantages of sufficient serum levels of vitamin C and the evaluation of the effects of vitamin C supplementation post kidney transplantation. These studies have been put together to investigate the role of vitamin C post-kidney transplantation and make suggestions for designing future studies based on the use of vitamin C supplements or nutritional interventions among these patients.

METHODS

This narrative review was done by searching in the Embase, PubMed, and SCOPUS databases.

RESULTS

The results are presented in several sections as follows; nutritional status, potential protective effects, safety concerns, and medications/laboratory tests interactions of vitamin C.

CONCLUSIONS

Kidney transplant recipients are prone to vitamin C deficiency, which is related to higher mortality based on several long-term observational studies. Vitamin C supplementation improves endothelial function and creatinine clearance. Vitamin C is considered as a safe supplement, however, side effects such as kidney stones, pro-oxidant effect, hemolysis in patients with glucose-6-phosphate dehydrogenase deficiency, impact on lymphocytic activity, acid-base disturbance, and increased sodium load following its administration have been reported. Interaction of vitamin C and cyclosporine is the most important interaction with post-renal transplant medications. Vitamin C also interferes with creatinine assay using Jaffe and enzymatic methods.

Differential expression of MAP3K7 and TROPONIN C proteins and related perturbations in renal amyloidosis

OBJECTIVES

Renal amyloidosis (RA) is a rare protein misfolding disorder that prompts progressive renal insufficiency. This study aimed to decipher proteomic changes in human sera to understand the pathophysiology and molecular mechanisms underlying the disease development, hence assisting in the diagnosis of RA.

METHODS

Serum proteomic analysis was performed using a gel-based approach followed by MALDI-TOF MS. RA patients with age and sex matched healthy volunteers were recruited from Max Super Speciality Hospital, New Delhi, India.

RESULTS

Proteome profiles of serum revealed eight differentially expressed proteins namely, Zinc finger protein 624, Protein FAM183A, Calcium-binding mitochondrial carrier protein Scamc-3, V-type proton ATPase 116 kDa subunit A isoforms 2, Protein TXNRD3NB, ATP - dependent RNA helicase, Troponin C and Mitogen-activated protein kinase kinase kinase 7. These proteins were reported first time in RA. The increased levels of MAP3K7 and TROPONIN C were validated by bio-layer interferometry and their diagnostic accuracy was evaluated by ROC curve analysis. The differentially expressed proteins were predominantly associated with vesicular trafficking, transcriptional regulation, metabolic processes, apoptotic process and mitochondrial metabolism.

CONCLUSION

The results indicate that these proteomic signatures may be considered as potential molecular targets for RA diagnostics and therapeutics subject to validation on large sample size. Abbreviations: AβP= Amyloid-beta protein, Aβ=Amyloid-beta, AL= Light chain amyloidosis, AA= Amyloid A, ALECT2= LECT2 amyloidosis, APS= Ammonium persulfate CKD= Chronic Kidney Diseases, EBRT= external beam radiation therapy, ESRD= End-Stage Kidney Disease, Glis2= Gli-similar 2, JNK= c-Jun NH 2-terminal kinase, MAPK= Mitogen-Activated Protein Kinase, MM=Multiple Myeloma, PHD= Prolyl hydroxylase, RA = Renal Amyloidosis, SAA= Serum Amyloid A, SD= Standard Deviation, Sepp= Selenoprotein, SCC= Squamous cell carcinoma, SDS= Sodium dodecyl sulfate, TEMED = tetramethyl ethylenediamine, TGF-Beta-1=Transforming growth factor- Beta-1, Trx = Thioredoxin, TrxR= Thioredoxin reductase.

Validation of multiparametric MRI by histopathology after nephrectomy: a case study

OBJECTIVES

Renal multiparametric MRI (mpMRI) is a promising tool to monitor renal allograft health to enable timely treatment of chronic allograft nephropathy. This study aims to validate mpMRI by whole-kidney histology following transplantectomy.

MATERIALS AND METHODS

A patient with kidney transplant failure underwent mpMRI prior to transplantectomy. The mpMRI included blood oxygenation level-dependent (BOLD) MRI, T₁ and T₂ mapping, diffusion-weighted imaging (DWI), 2D phase contrast (2DPC) and arterial spin labeling (ASL). Parenchymal mpMRI measures were compared to normative values obtained in 19 healthy controls. Differences were expressed in standard deviations (SD) of normative values. The mpMRI measures were compared qualitatively to histology.

RESULTS

The mpMRI showed a heterogeneous parenchyma consistent with extensive interstitial hemorrhage on histology. A global increase in T₁ (+ 3.0 SD) and restricted diffusivity (- 3.6 SD) were consistent with inflammation and fibrosis. Decreased T₂ (- 1.8 SD) indicated fibrosis or hemorrhage. ASL showed diminished cortical perfusion (- 2.9 SD) with patent proximal arteries. 2DPC revealed a 69% decrease in renal perfusion. Histological evaluation showed a dense inflammatory infiltrate and fibrotic changes, consistent with mpMRI results. Most interlobular arteries were obliterated while proximal arteries were patent, consistent with ASL findings.

DISCUSSION

mpMRI findings correlated well with histology both globally as well as locally.

Lactobacillus acidophilus Endocarditis Complicated by Pauci-Immune Necrotizing Glomerulonephritis

Infective endocarditis (IE) is more common in patients with predisposing cardiac lesions and has many potential complications, including stroke and arterial thromboembolisms. Renal manifestations have an estimated prevalence of ∼20%. Rapidly progressive glomerulonephritis (RPGN) is a nephrological emergency manifested by autoimmune-mediated progressive loss of renal function over a relatively short period of time. Here, we report the case of a 60-year-old Caucasian male, who presented with speech impairment and was found to have multiple embolic strokes caused by aortic valve IE. His renal function declined rapidly, and his urine sediment featured hematuria and proteinuria. ANCA titer was negative by immunofluorescence (IF); however, the PR3 antibody was elevated. The renal biopsy revealed pauci-immune focally necrotizing glomerulonephritis with the presence of ∼25% cellular crescents. He was initially treated with plasmapheresis and pulse dose steroids. Hemodialysis was initiated for uremic symptoms. After four weeks of antibiotic therapy and with blood cultures remaining negative, he was treated with rituximab. Two months after discharge, his renal function showed improvement, and hemodialysis was discontinued. This case highlights several complications associated with lactobacillus endocarditis including RPGN.

Utility of transjugular renal biopsy as an alternative to percutaneous biopsy

BACKGROUND AND OBJECTIVES

Transjugular renal biopsies (TRB) are an alternative when percutaneous ultrasound renal biopsy is contraindicated. Few sites are currently carrying out this procedure, with limited literature existing on the indications, complications and diagnostic yield thereof. The aim of the study is to analyse the indications, diagnostic yield, safety and complications of percutaneous transjugular renal biopsies in our site over the last 15 years.

MATERIAL AND METHODS

Retrospective descriptive study of all transjugular renal biopsies performed in our site, the Hospital Vall d'Hebron, between 2003 and 2018. For this, an exhaustive review of the clinical records of patients subjected to this procedure during the study period was conducted.

RESULTS

56 TRBs were performed during the study period. Out of the patients, 31 were men (55.4%) and 25 were women (44.6%), with a median age of 62 years (IQ range 25-75 [52.5-69.5]). More than half presented with haematuria at the time of biopsy, with a median creatinine of 2.69 mg/dL (IQ 25-75 [1.7-4.3]) and median proteinuria at 24 hours of 2000 mg (IQ 25-75 [0.41-4.77]).The mean systolic blood pressure (SBP) and diastolic blood pressure (DBP) were 140 +/- 26 mmHg and 75 +/- 15 mmHg, respectively. The biopsy was carried out owing to acute kidney failure in 19 patients, chronic kidney disease in 12 patients and nephrotic syndrome in 10 patients; in 15 patients it was carried out for other reasons. The most frequent TRB indication was technical impossibility in 16 of 56 cases (including infracostal kidneys, obesity and COPD), alterations in haemostasis (n = 6), thrombocytopenia (n = 5) and solitary kidney (n = 7). 12.5% of the biopsies were hepato-renal. Histological diagnoses were obtained in two thirds of the renal biopsies. The average number of cylinders obtained was 2.5 ± 1.3, with the average number of glomeruli being 6.6 ± 6.2. The most frequent histological diagnoses were IgA nephropathy, membranoproliferative glomerulonephritis and thrombotic microangiopathy. Three major complications were observed: fornix rupture and two transfusion requirements due to bleeding and subcapsular hematoma.

CONCLUSIONS

In our site, TRB allowed for a histological diagnosis in 2/3 of patients for whom percutaneous ultrasound renal biopsy is contraindicated. This allowed us to diagnose and subsequently treat said patients.

Frequency, Timing, and Prediction of Major Bleeding Complications From Percutaneous Renal Biopsy

Background and Objectives:

The risk and timing of bleeding events following ultrasound-guided percutaneous renal biopsy are not clearly defined.

Design setting, participants, and measurements:

We performed a retrospective study of 617 consecutive adult patients who underwent kidney biopsy between 2012 and 2017 at a tertiary academic hospital in London, Canada. We assessed frequency and timing of minor (not requiring intervention) and major (requiring blood transfusion, surgery, or embolization) bleeds and developed a personalized risk calculator for these.

Results:

Bleeding occurred in 79 patients (12.8%; 95% confidence interval [CI]: 10.4%-15.7%). Minor bleeding occurred in 67 patients (10.9%; 95% CI: 8.6%-13.6%). Major bleeding occurred in 12 patients (1.9%; 95% CI: 1.1%-3.4%); 2 required embolization or surgery (0.3%; 95% CI: 0.09%-1.2%) and 10 required blood transfusion (1.6%; 95% CI: 0.9%-3.0%). Seventy-three of 79 events were identified immediately on post-procedure ultrasound (92.4% of cases; 95% CI: 84.4%-96.5%). Four of 617 patients experienced a minor event not detected immediately (0.6%; 95% CI: 0.3%-1.7%). Two patients (0.3%; 95% CI: 0.09%-1.2%) suffered a major complication that was not recognized immediately; both required blood transfusions only. There were no deaths or nephrectomies. A risk calculator using age, body mass index, platelet count, hemoglobin concentration, size of the target kidney, and whether the kidney is native, or an allograft predicted minor (C-statistic, 0.70) and major bleeding (C-statistic, 0.83).

Conclusions:

This retrospective study of 617 patients who had percutaneous ultrasound-guided renal biopsies supports the safety of short post-biopsy monitoring for most patients. A risk calculator can further personalize estimates of complication risk (http://perioperativerisk.com/kbrc).

Urinary MicroRNA-21-5p as Potential Biomarker of Interstitial Fibrosis and Tubular Atrophy (IFTA) in Kidney Transplant Recipients

Chronic renal allograft dysfunction (CAD) is a major limiting factor of long-term graft survival. The hallmarks of progressive CAD are interstitial fibrosis and tubular atrophy (IFTA). MicroRNAs are small, regulatory RNAs involved in many immunological processes. In particular, microRNA-21-5p (miR-21) is considered to be strongly associated with pathogenesis regarding tubulointerstitium. The aim of this study was to assess urinary miR-21 expression levels in the kidney transplant recipients and determine their application in the evaluation of IFTA and kidney allograft function. The expression levels of miR-21 were quantified in the urine of 31 kidney transplant recipients with biopsy-assessed IFTA (IFTA 0 + I: n = 17; IFTA II + III: n = 14) by real-time quantitative PCR. Urine samples were collected at the time of protocolar biopsies performed 1 or 2 years after kidney transplantation. MicroRNA-191-5p was used as reference gene. MiR-21 was significantly up-regulated in IFTA II + III group compared to IFTA 0 + I group (p = 0.003). MiR-21 correlated significantly with serum concentration of creatinine (r = 0.52, p = 0.003) and eGFR (r = -0.45; p = 0.01). ROC analysis determined the diagnostic value of miR-21 with an area under curve (AUC) of 0.80 (p = 0.0002), sensitivity of 0.86 and specificity of 0.71. miR-21 is associated with renal allograft dysfunction and IFTA. Therefore, it could be considered as a potential diagnostic, non-invasive biomarker for monitoring renal graft function.

Molecular Imaging of the Glomerulus via Mesangial Cell Uptake of Radiolabeled Tilmanocept

An unmet need for the clinical management of chronic kidney disease is a predictive tool of kidney function during the first decade of the disease, when there is silent loss of glomerular function. The objective of this study was to demonstrate receptor-mediated binding of tilmanocept to CD206 within the kidney and provide evidence of kinetic sensitivity of this binding to renal function. Methods: Rats were positioned in a PET scanner with the liver and kidneys within the field of view. After an intravenous injection of 68Ga-IRDye800-tilmanocept, using 1 of 2 scaled molar doses (0.02 nmol/g, n = 5; or 0.10 nmol/g, n = 5), or coinjection (n = 3) of 68Ga-IRDye800-tilmanocept (0.10 nmol/g) and unlabeled tilmanocept (5.0 nmol/g), or a negative control, 68Ga-IRDye800-DTPA-galactosyl-dextran (0.02 nmol/g, n = 5), each animal was imaged for 20 min followed by a whole-body scan. Frozen kidney sections were stained for podocytes and CD206 using immunofluorescence. Molecular imaging of diabetic db/db mice (4.9 wk, n = 6; 7.3 wk, n = 4; 13.3 wk, n = 6) and nondiabetic db/m mice (n = 6) was performed with fluorescence-labeled 99mTc-tilmanocept (18.5 MBq, 2.6 nmol). Thirty minutes after injection, blood, liver, kidneys, and urine were assayed for radioactivity. Renal time-activity curves were generated. Results: Rat PET whole-body images and time-activity curves of 68Ga-IRDye800-tilmanocept demonstrated receptor-mediated renal accumulation with evidence of glomerular uptake. Activity within the renal cortex persisted during the 40-min study. Histologic examination demonstrated colocalization of CD206 and IRDye800-tilmanocept within the glomerulus. The glomerular accumulation of the coinjection and the negative control studies were significantly less than the CD206-targeted agent. The db/db mice displayed a multiphasic renal time-activity curve with high urinary bladder accumulation; the nondiabetic mice exhibited renal uptake curves dominated by a single phase with low bladder accumulation. Conclusion: This study demonstrated receptor-mediated binding to the glomerular mesangial cells and kinetic sensitivity of tilmanocept to chronic renal disease. Given the role of mesangial cells during the progression of diabetic nephropathy, PET or SPECT renal imaging with radiolabeled tilmanocept may provide a noninvasive quantitative assessment of glomerular function.

Evolving spectrum of diabetic nephropathy

Diabetes remains an important health issue as more patients with chronic and uncontrolled diabetes develop diabetic nephropathy (DN), which classically presents with proteinuria followed by a progressive decrease in renal function. However, an increasing proportion of DN patients have a decline in kidney function and vascular complications without proteinuria, known as non-proteinuric DN (NP-DN). Despite the increased incidence of NP-DN, few clinical or experimental studies have thoroughly investigated the pathophysiological mechanisms and targeted treatment for this form of DN. In this review, we will examine the differences between conventional DN and NP-DN and consider potential pathophysiological mechanisms, diagnostic markers, and treatment for both DN and NP-DN. The investigation of the pathophysiology of NP-DN should provide additional insight into the cardiovascular factors influencing renal function and disease and provide novel treatments for the vascular complications seen in diabetic patients.

Complications and Risks of Percutaneous Renal Biopsy

BACKGROUND

Renal biopsy performed in native and transplant kidneys is generally considered a safe procedure.

AIM

In this study, we evaluated renal biopsy complications and risk factors in one nephrology facility.

MATERIAL AND METHODS

We conducted a three-year retrospective study on patients who underwent renal biopsy between January 2014 and December 2016. Strict written biopsy protocol was followed. Clinical and laboratory data were obtained from medical charts. Complications were categorised as minor and major, according to the need for intervention. Minor complications included macrohematuria and/or hematoma that did not require intervention. Major complications included hematuria or hematoma with fall of hematocrit that required a blood transfusion, surgery or caused death. A binary logistic regression model was used to analyse the possible factors associated with complications after the biopsy.

RESULTS

We analysed 345 biopsies; samples were taken from patients aged from 15-81 years, of whom 61% were men. A total of 21 (6%) patients developed a complication, 4.4% minor and 1.7% major complications. There were no nephrectomy or death due to biopsy intervention. Overweight patients, as well as those with higher creatinine, lower hemoglobin, higher blood pressure and biopsy due to AKI had higher chances to develop complications (p = 0.037, p = 0.023, p = 0.032, p = 0.002, p = 0.002, respectively). The patients' age, gender, kidney dimension, number of passes and uninterrupted aspirin therapy were not found as significant predictors of complications. In the multivariate logistic model, body weight (OR = 1.031, 95%CI = 1.002-1.062), lower hemoglobin (OR = 0.973, 95%CI = 0.951-0.996) and hypertension (OR = 1.025, 95%CI = 1.007-1.044) increased the risk of complications in biopsied patients.

CONCLUSION

Renal biopsy is a safe procedure with a low risk of complications when strict biopsy protocol is observed. Correction of anaemia and blood pressure is to be considered before the biopsy.

Comparing laparoscopic and percutaneous renal biopsy for diagnosing native kidney disease: A matched pair analysis

BACKGROUND

Percutaneous renal biopsy is a well-established diagnostic procedure in patients with underlying medical renal disease. Aim of this study is to compare the adequacy of the biopsy material, the diagnostic yield, and the complication rates of the trans-peritoneal laparoscopic approach and the image-guided percutaneous approach to renal biopsy in the diagnosis of native kidney disease.

METHODS

We performed a matched-pair analysis matching 1:3 40 patients who underwent trans-peritoneal laparoscopic renal biopsy to 120 patients who underwent percutaneous renal biopsy in the same years. Patients were retrospectively analyzed. Differences in adequacy of biopsy material (i.e. number of glomeruli, continuous), diagnostic yield (categorical) and postoperative complications across the two groups were assessed using Wilcoxon Rank sum or χ² test.

RESULTS

Laparoscopic biopsy was associated with a higher number of harbored glomeruli (median 50, IQR 20-77) compared to the percutaneous approach (median 10, IQR 7-15), P<0.001. Adequate biopsies containing at least ten glomeruli were obtained in a significantly higher percentage of patients in the laparoscopic group versus the percutaneous group (92.5% vs. 57.1%, P<0.001). The laparoscopic approach was also associated with a significantly higher diagnostic yield than the percutaneous approach (82.5% vs. 63.5%, P=0.027). Patients who underwent laparoscopic biopsy had no perioperative or postoperative complications, resulting in a significantly lower complication rate than percutaneous biopsy (0% vs. 4%, P<0.001), particularly in the need for transfusion for post-procedure bleeding (0% vs. 1.8%, P<0.001).

CONCLUSIONS

In this retrospective matched-pair analysis comparing patients undergoing renal biopsy for medical kidney disease, trans-peritoneal laparoscopic renal biopsy was safer and more effective for the diagnosis of medical renal diseases compared to percutaneous renal biopsy. Prospective trials with a good follow-up are needed to define the best candidate for each approach.

LEVEL OF EVIDENCE

4.

Manual compression and reflex syncope in native renal biopsy

BACKGROUND

Complications associated with diagnostic native percutaneous renal biopsy (PRB) must be minimized. While life threatening major complications has been extensively investigated, there is little discussion regarding minor bleeding complications, such as a transient hypotension, which directly affect patients' quality of life. There is also little evidence supporting the need for conventional manual compression following PRB. Therefore, this study evaluated the relationship between minor and major complications incidence in patients following PRB with or without compression.

METHODS

This single-center, retrospective study included 456 patients (compression group: n = 71; observation group: n = 385). The compression group completed 15 min of manual compression and 4 h of subsequent strict bed rest with abdominal bandage. The observation group completed 2 h of strict bed rest only. The primary outcome of interest was transient symptomatic hypotension (minor event).

RESULTS

Of the 456 patients, 26 patients encountered intraoperative and postoperative transient hypotension, which were considered reflex syncope without tachycardia. Univariate analysis showed that symptomatic transient hypotension was significantly associated with compression. This association remained significant, even after adjustment of covariates using multivariate logistic regression analysis (adjusted odds ratio 3.27; 95% confidential interval 1.36-7.82; P = 0.0078).

CONCLUSION

Manual compression and abdominal bandage significantly increased the frequency of reflex syncope during native PRB. It is necessary to consider the potential benefit and risk of compression maneuvers for each patient undergoing this procedure.

Drug-Induced Hematological Cytopenia in Kidney Transplantation and the Challenges It Poses for Kidney Transplant Physicians

Drug-induced hematological cytopenia is common in kidney transplantation. Various cytopenia including leucopenia (neutropenia), thrombocytopenia, and anemia can occur in kidney transplant recipients. Persistent severe leucopenia or neutropenia can lead to opportunistic infections of various etiologies. On the contrary, reducing or stopping immunosuppressive medications in these events can provoke a rejection. Transplant clinicians are often faced with the delicate dilemma of balancing cytopenia and rejection from adjustments of immunosuppressive regimen. Differentials of drug-induced cytopenia are wide. Identification of culprit medication and subsequent modification is also challenging. In this review, we will discuss individual drug implicated in causing cytopenia and correlate it with corresponding literature evidence.

Measurements of renal shear wave velocities in chronic kidney disease patients

Background Chronic kidney disease (CKD) patients have advanced glomerulosclerosis and renal interstitial fibrosis. Shear wave elastography (SWE) is useful to diagnose liver fibrosis. However, there are few data available regarding evaluation of kidney function on the use of SWE. Purpose To assess the utility of SWE by evaluating the correlation between renal function and renal elasticity using SWE. Material and Methods A total of 187 participants who had available serum creatinine levels and also underwent SWE of the kidney using a transabdominal ultrasonography were recruited at Nagoya University Hospital. We measured the depth of the shear wave (SW) in the right and left kidneys and calculated the measurement success rates. The glomerular filtration rate (GFR) classification and shear wave value (SWV) were compared. Results The success rates of the right and left kidneys were 93.6% and 71.6%, respectively. Based on these results, the correlation between GFR classification and SWV were analyzed in only the right kidneys because the success rates and the number of enrolled patients were low for the left kidney. There were significant differences found between G1 and G3a, G2 and G3a, G3a and G3b, G3a and G4, and G3a and G5. SWV significantly negatively and positively correlated with the G2-G3a and G3a-G3b classifications. Conclusion There is no correlation between renal function and SW. However, we can diagnose the progression to the CKD stages G3a and G3b by observing the changes over time using the SWV.

Characterization and Etiopathogenic Approach of Pediatric Renal Biopsy Patients in a Colombian Medical Center from 2007-2017

Introduction

Renal biopsy is the principal instrument to evaluate the diagnosis and prognosis of children with kidney disease. There are relatively few studies establishing epidemiology of its findings in the pediatric population.

Methods

A descriptive study was conducted to describe characteristics of pediatric patients who had undergone a renal biopsy over the last 10 years in a national reference center, trying to accomplish an etiopathogenic approach of biopsy findings.

Results

241 patients were included. Most frequent indications were nephrotic syndrome (34.1%) and systemic disease with renal involvement (30.2%). The most prevalent biopsy diagnosis was glomerulonephritis (44%) and among these patients, glomerulonephritis mediated by immune complexes was the most frequent pathogenic type (90.5%). When the biopsy was indicated for proteinuria plus hematuria and systemic disease with renal involvement, the most frequent biopsy diagnosis was glomerulonephritis (60 and 85%, respectively). For isolated hematuria, the predominant biopsy diagnosis was inherited diseases of the glomerular basement membrane (70%) and for nephrotic syndrome, podocytopathy (82%). Glomerulonephritis was more frequent in patients older than 10 yrs (65%) and the rate of postbiopsy major complications was low (1.2%).

Conclusion

Immune complex glomerulonephritis was the most frequent histological finding, differing from previous reports. To our knowledge this is the first description that classifies biopsy findings according to the probable pathogenic mechanism.

Routine haemostasis testing before transplanted kidney biopsy: a cohort study

Kidney biopsy can result in bleeding complications. Prebiopsy testing using bleeding time (BT) is controversial. New whole blood haemostasis tests, such as platelet function analyser-100 (PFA-100) and multiple electrode aggregometry (MEA), might perform better. We postulated that PFA-100 would be suitable to replace BT prebiopsy. In 154 patients, transplanted kidney biopsies were performed after measurement of bleeding time, PFA-100, MEA and mean platelet volume (MPV). Bleeding outcome (haemoglobin (Hb) drop, haematuria (±bladder catheterization), ultrasound finding of a bleeding, need for (non)surgical intervention and/or transfusion) after the biopsy was correlated to each test. Male-female ratio was 2:1. 50% had a surveillance biopsy at either three or 12 months. Around 17% (had) used acetylsalicylic acid (ASA) prebiopsy. Of 17 bleeding events, one subject needed a transfusion. Most bleeding events were Hb reductions over 1 mmol/l and all resolved uneventful. BT, PFA-100, MEA and MPV did not predict a bleeding outcome; prior ASA use however could (odds ratio 3.19; 95%-CI 1.06 to 9.61). Diagnostic performance data and Bland-Altman analysis showed that BT could not be substituted by PFA-100. ASA use was the best determinant of bleeding after kidney biopsy. Routine haemostasis testing prebiopsy has no added value.

Warfarin-related nephropathy in a patient with renal pelvic cancer

An 83-year-old Japanese man had a history of chronic heart failure due to bradycardia-tachycardia syndrome. He was admitted to our hospital because of macrohematuria and acute kidney injury (AKI), which were detected by an urologist at an outpatient visit. He had a history of recurrent macrohematuria and transurethral resection of bladder tumors twice in the preceding 2 years. He had been on warfarin for 12 years, with a stable international normalized ratio (INR) that was usually less than 2.1. Urinalysis revealed numerous red blood cells (RBCs) and mild proteinuria without RBC casts. His serum creatinine level was elevated to 2.41 mg/dL from 0.96 mg/dL at 3 weeks before admission. INR was 1.44. Hydronephrosis was not observed. Ureteroscopy detected invasive urothelial carcinoma of the renal pelvis, and right laparoscopic nephroureterectomy was performed at 41 days after diagnosis of AKI. The background renal parenchyma displayed tubular obstruction by red blood cell casts and acute tubular injury, which were changes compatible with warfarin-related nephropathy (WRN). Warfarin was discontinued, and the serum creatinine level recovered to 1.66 mg/dL after 3 months. In the present patient with nephrosclerosis, WRN occurred at a therapeutic INR level after 12 years of uneventful warfarin therapy, and the coexisting urothelial malignancy was a unique feature.

Coagulopathy as a complication of kidney biopsies in paediatric systemic lupus erythematosus patients with antiphospholipid syndrome

Children with systemic lupus erythematosus (SLE) generally undergo a pretreatment kidney biopsy. However, some of these patients, especially those with antiphospholipid syndrome (APS), may experience serious coagulopathic complications. We report herein two cases of paediatric SLE with APS in which, despite normal blood test results, the disparate coagulopathic complications of haemorrhage and embolism developed following a kidney biopsy. Case 1 was, an 8-year-old male in whom, primary APS was initially diagnosed. Fourteen months later SLE was diagnosed. Based on a percutaneous kidney biopsy, International Society of Nephrology and the Renal Pathology Society (ISN/RPS) class III-A lupus nephritis was histologically diagnosed. On post-biopsy Day 9, a giant haematoma in the fascia of the left kidney developed and was accompanied by changes in the vital signs. Case 2, a 13-year-old male, initially received the diagnosis of SLE with APS and underwent two courses of pulse methylprednisolone therapy. His coagulation abnormalities improved, and a percutaneous needle kidney biopsy was performed, leading to the histological diagnosis of ISN/RPS class III-A lupus nephritis. Furthermore, thrombotic microangiopathy was also detected in the renal histopathology. On post biopsy Day 6, the patient experienced right leg pain. A contrast CT and lower extremity ultrasonography detected a massive deep vein thrombosis and partial left pulmonary artery thrombosis. A kidney biopsy in children with SLE and APS can cause lethal coagulopathic complications, and the risks to such patients should be weighed carefully before the procedure is performed.

Measuring hemoglobin prior to early discharge without routine surveillance ultrasound after percutaneous native renal biopsy in children

BACKGROUND

We aimed to evaluate the role of post-procedural hemoglobin (hb), without pre-discharge ultrasound (US), after US-guided renal biopsy in children.

METHODS

A retrospective review was conducted of consecutive outpatient native kidney biopsies over an 8-year period. Procedures were performed under real-time US guidance. Data collected included number of passes, presence and size of perinephric hematoma, age, body mass index (BMI), blood pressure (BP), fasting status, hb and platelets. Continuous variables were expressed as mean ± standard deviation, group differences were tested with Student's unpaired t test and analysis of variance and correlations were assessed using Pearson's r. Significance was defined as p < 0.05. Hb changes (g/L), percentage hb (%hb) change, hematoma size and positive and negative predictive values (PPV, NPV, respectively) were analyzed.

RESULTS

A total of 330 procedures in 300 children (141 females, mean age 11.2 ± 4.30 years) were analyzed. Post-procedural hematoma occurred in 63%. There was a significant (p = 0.0001) post-procedural hb decrease of 6.3 ± 5.5 g/L and %hb decrease of 4.56 ± 4.01%. Fasting during pre-procedural hb estimation and procedural hematoma was associated with a greater hb drop. A ≥10% hb drop had 73% PPV for repeat blood work and US and a 17% PPV for admission, whereas a <10% hb drop had a NPV of 84% and 98%, respectively. Hb change showed a weak correlation with age, and hematoma size showed a weak inverse correlation with platelet count, but no correlation with BMI, number of passes or BP.

CONCLUSIONS

Bleeding complications from US-guided native kidney biopsies in pediatric outpatients can be safely followed by a complete blood count at 6 h post procedure. A 10% hb decrease is strongly associated with requirement for further testing and/or admission.

Diagnostic work-up and specific causes of acute kidney injury

Acute kidney injury (AKI) is common in critically ill patients and associated with grim short- and long-term outcome. Although in the vast majority of cases AKI is multifactorial, with sepsis, shock and nephrotoxicity accounting for most episodes, specific causes of AKI are not uncommon. Despite remaining uncertainties regarding their prevalence in the ICU, prompt recognition of specific aetiologies of AKI is likely to ensure timely management, limit worsening of renal dysfunction, and ultimately limit renal and systemic consequences of AKI. The ability to recognize conditions that may be associated with specific aetiologies and the appropriate use of clinical imaging, biological and immunological tests, along with optimal assessment of the need for renal biopsies, should be part of routine ICU care. In this review, we summarize uncertainties, current knowledge and recent advances regarding specific types of AKI. We describe the most common specific causes as well as rare aetiologies requiring urgent management, and outline available tools that may be used during the diagnostic work-up along with their limitations.

Percutaneous perirenal thrombin injection for the treatment of acute hemorrhage after renal biopsy

Percutaneous renal biopsy is a valuable diagnostic approach. While commonly safe, it is not without risk and the most feared vascular complications include hemorrhage, pseudoaneurysm, and arteriovenous fistula formation. We report a case of acute hemorrhage after renal biopsy that was immediately identified by ultrasonography and successfully treated with percutaneous perirenal thrombin injection. This technique may prove a useful addition to the armamentarium of any operator performing renal biopsies.