Renal biopsy: Still a landmark for the nephrologist

Comparative analysis of ultrasound-guided percutaneous biopsy of native kidneys in children and adults using the free-flank supine antero-lateral decubitus positioning

PURPOSE

Ultrasound-guided percutaneous biopsy (USPB) of the native kidneys is the preferred diagnostic method for several nephrological conditions in both adult and pediatric populations. Conventionally, native kidney biopsies are conducted with patients in the prone position (PP). However, an alternative approach involving the supine oblique antero-lateral position (SALP) has been explored, particularly for individuals who are obese, elderly, or critically ill.

METHODS

This study aimed to assess the feasibility and outcomes of USPB performed in SALP with a Free-Flank setting (FF-SALP) in pediatric patients (Group A) compared to adults (Group B). Data from kidney biopsies conducted between 2008 and 2021 were gathered. The study focused on the safety and the prevalence of biopsy samples containing a minimum of 10 glomeruli, histopathological yield in both groups.

RESULTS

Complication rates were low in both groups (5.6% vs. 3.7%; p = 0.454), without major complications noted. The pediatric group achieved a significantly higher mean number of glomeruli per biopsy compared to the adult group (20.6 ± 12.3 vs. 15.7 ± 9.4; p < 0.001). However, when evaluating the minimum threshold of 10 glomeruli (76.3% vs. 68.5%; p = 0.072) and histopathologic yield (95.3% vs. 93.5%; p = 0.408), no differences were observed between groups.

CONCLUSION

USPB of native kidneys in the FF-SALP position is a safe and effective method for tissue sampling in patients with parenchymal disease. It demonstrated comparable diagnostic yields and complication rates in the pediatric and adult populations, providing advantages in terms of airway management, making it particularly useful for pediatric patients that require general anesthesia.

Construction of artificial intelligence non-invasive diagnosis model for common glomerular diseases based on hyperspectral and urine analysis

OBJECTIVE

To develop a non-invasive fluid biopsy assisted diagnosis model for glomerular diseases based on hyperspectral, so as to solve the problem of poor compliance of patients with invasive examination and improve the early diagnosis rate of glomerular diseases.

METHODS

A total of 65 urine samples from patients who underwent renal biopsy from November 2020 to January 2022 in Qianfoshan Hospital of Shandong Province were collected.By simultaneously capturing spectral information of the above urine samples in the 400-1000 nm range, more obvious differences were found in the spectra of urine from patients with glomerular diseases between 650 nm and 680 nm. We obtained the original hyperspectral images in this wavelength range through digital scanning, and sampled pixel points at intervals on the original images. The two-dimensional digital image generated from each pixel point served as a member of the subsequent training and test sets. . After manually labeling the images according to different biopsy pathological types, they were randomly divided into training set (n = 58,800) and test set (n = 25,200). The training set was used for training learning and parameter iteration of artificial intelligence non-invasive liquid diagnosis model, and the test set for model recognition and interpretation. The evaluation indexes such as accuracy, sensitivity and specificity were calculated to evaluate the performance of the diagnosis model.

RESULTS

The model has an accuracy rate of 96% for early diagnosis of four glomerular diseases.

CONCLUSION

The auxiliary diagnosis model system has high accuracy. It is expected to be used as a non-invasive diagnostic method for glomerular diseases in clinic.

Comparison of outcomes of an 18-gauge vs 16-gauge ultrasound-guided percutaneous renal biopsy: a systematic review and meta-analysis

Background: The needle size used in ultrasound-guided percutaneous renal biopsy significantly influences the efficacy and safety of the procedure. The aim of this study is to perform a comparative analysis of 16-gauge and 18-gauge needles for ultrasound-guided percutaneous renal biopsy.Methods: This systematic review and meta-analysis included randomized controlled trials and observational studies that compared the outcomes of using 18-gauge and 16-gauge needles for ultrasound-guided percutaneous renal biopsy. The efficacy parameters included a mean number of glomeruli obtained and the number of passes, while the safety parameters focused on the rate of complications. We searched multiple databases, assessed the risk of bias, and conducted statistical analyses using appropriate models.Results: Fifteen studies were included. Compared to the 18-gauge needle, the use of 16-gauge needle for the biopsy was associated with the significantly higher mean number of glomeruli obtained (pooled SMD 0.61, 95%CI: 0.32 to 0.89; p < 0.001) and fewer required passes (pooled SMD -0.57, 95%CI: -0.97 to -0.18; p = 0.004). No significant difference was observed in the individual safety parameters, including pain, hematuria, need for blood transfusion, major, and minor complications. However, the use of 16-gauge needle was associated with higher odds of total complications (pooled OR 1.57, 95%CI: 1.16 to 2.13; p = 0.004).Conclusion: While the 16-gauge needle for ultrasound-guided percutaneous renal biopsy offers improved efficacy in terms of a higher mean number of glomeruli and fewer required passes, it is associated with higher total complications. A judicious needle size selection that would consider patient-specific factors and risk-benefit ratio, is crucial for optimizing patient outcomes.

Urinary markers differentially associate with kidney inflammatory activity and chronicity measures in patients with lupus nephritis

OBJECTIVE

Lupus nephritis (LN) is diagnosed by biopsy, but longitudinal monitoring assessment methods are needed. Here, in this preliminary and hypothesis-generating study, we evaluate the potential for using urine proteomics as a non-invasive method to monitor disease activity and damage. Urinary biomarkers were identified and used to develop two novel algorithms that were used to predict LN activity and chronicity.

METHODS

Baseline urine samples were collected for four cohorts (healthy donors (HDs, n=18), LN (n=42), SLE (n=17) or non-LN kidney disease biopsy control (n=9)), and over 1 year for patients with LN (n=42). Baseline kidney biopsies were available for the LN (n=46) and biopsy control groups (n=9). High-throughput proteomics platforms were used to identify urinary analytes ≥1.5 SD from HD means, which were subjected to stepwise, univariate and multivariate logistic regression modelling to develop predictive algorithms for National Institutes of Health Activity Index (NIH-AI)/National Institutes of Health Chronicity Index (NIH-CI) scores. Kidney biopsies were analysed for macrophage and neutrophil markers using immunohistochemistry (IHC).

RESULTS

In total, 112 urine analytes were identified from LN, SLE and biopsy control patients as both quantifiable and overexpressed compared with HDs. Regression analysis identified proteins associated with the NIH-AI (n=30) and NIH-CI (n=26), with four analytes common to both groups, demonstrating a difference in the mechanisms associated with NIH-AI and NIH-CI. Pathway analysis of the NIH-AI and NIH-CI analytes identified granulocyte-associated and macrophage-associated pathways, and the presence of these cells was confirmed by IHC in kidney biopsies. Four markers each for the NIH-AI and NIH-CI were identified and used in the predictive algorithms. The NIH-AI algorithm sensitivity and specificity were both 93% with a false-positive rate (FPR) of 7%. The NIH-CI algorithm sensitivity was 88%, specificity 96% and FPR 4%. The accuracy for both models was 93%.

CONCLUSIONS

Longitudinal predictions suggested that patients with baseline NIH-AI scores of ≥8 were most sensitive to improvement over 6-12 months. Viable approaches such as this may enable the use of urine samples to monitor LN over time.

Indicadores clínicos da Nursing Outcomes Classification para avaliar o paciente submetido à biópsia renal percutânea

Objetivos: selecionar indicadores clínicos dos resultados de Enfermagem Coagulação Sanguínea (0409), Estado Circulatório (0401), Gravidade da perda de Sangue (0413), Nível de dor (2102) e Estado de Conforto: físico (2010) da Nursing Outcomes Classification e elaborar suas definições conceituais e operacionais para avaliação de pacientes submetidos à biópsia renal percutânea. Método: estudo de consenso de especialistas realizado em um hospital universitário do Sul do Brasil. A amostra foi de 12 especialistas. A coleta de dados ocorreu por meio de formulário eletrônico no Google Forms, no qual foram listados os indicadores clínicos a serem selecionados para avaliar pacientes submetidos ao procedimento de biópsia renal. Foram selecionados os indicadores que obtiveram concordância mínima de 80% entre os especialistas. Os dados foram organizados em um quadro para a elaboração das definições de cada indicador. Resultados: foram selecionados 11 indicadores clínicos: sangramento, hematoma, hematúria, pressão arterial sistólica, pressão arterial diastólica, distensão abdominal, palidez da pele e das mucosas, dor relatada, expressões faciais de dor, bem-estar físico e posição confortável. Posteriormente, com base na literatura, foram elaboradas as definições conceituais e operacionais para esses indicadores. Conclusão: os indicadores clínicos selecionados estão em consonância com as possíveis complicações da biópsia renal percutânea descritas na literatura, podendo auxiliar os enfermeiros na avaliação dos pacientes submetidos ao procedimento. Infere-se que as definições conceituais e operacionais reduzem a subjetividade e facilitam avaliações mais acuradas dos pacientes na prática clínica.

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

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

Kidney biopsy-based epidemiologic analysis shows growing biopsy rate among the elderly

Systematic registration and examination of biopsy-related data in Central and Eastern Europe are scarce, while the health condition of the population is worse compared to other more developed countries. We aim to create a database and analyze the distribution and temporal variation of the renal biopsy diagnoses in Hungary, including the effect of the recent coronavirus pandemic. The diagnoses were standardized according to the recommendation of the European Renal Association. Native biopsy samples processed between January 1, 2006, and December 31, 2020, were analyzed. During the 15 years, 2140 native kidney biopsies were performed. The number of samples increased from 24.5 to 57.9 per million person-years and the median age from 37 to 51 years (p < 0.0001). The predominance of glomerular diseases was stable. The most frequent glomerulopathy was IgA nephropathy (21.5%), followed by focal segmental glomerulosclerosis (17.7%), and membranous nephropathy (15.7%). Trends showed the rise of ANCA-associated vasculitis. During the coronavirus pandemic, there was a decrease in the number of kidney biopsies and the proportion of membranous nephropathies. The diagnostic trends in our database showed increasing biopsy rates among the elderly and the growing frequencies of age-related diseases, which emphasizes the importance of altering medical focus according to demographic changes in this area.

Multimodality imaging evaluation of pseudotumors in chronic renal dysfunction: exposing the masquerade!

Focal renal lesions in the background of chronic kidney disease (CKD) present a diagnostic challenge. Contrast administration is usually avoided in such a setting, undermining the usefulness of computed tomography and magnetic resonance imaging. Focal regenerating nodules may occur in the background of CKD and closely mimic renal neoplasms. The aim of the present article was to highlight the salient manifestations of such CKD pseudotumors on different imaging modalities and also to depict the differentiating features from malignancy. Radiologists must be aware of the imaging appearance of this uncommonly talked about entity so as to avoid inadvertent surgery or cause undue anxiety to the patient.

Application of B-ultrasound information image in Renal Puncture Biopsy treatment and Nursing

Objectives

This study was to explore the application value of B-ultrasound in guiding puncture biopsy of chronic kidney disease (CKD) and the clinical nursing effects under the guidance of B-ultrasound.

Methods

Pathological examination of kidney biopsy was performed on 94 patients with CKD under the guidance of ultrasound from August 2020 to December 2020.; patients were observed for symptoms such as low back pain, backache, hematuria, and subcapsular hematoma. Color Doppler ultrasonography was performed on the punctured patients on day 1, 2, and 3 to observe whether there was subrental hematoma. The pathological results were analyzed and the success rate of percutaneous renal biopsy under ultrasound guidance was analyzed. Before the patient was discharged, investigate the satisfaction with the nursing work.

Results

(1) After the puncture, 45 patients developed low back pain and low back pain symptoms, 12 cases developed subcapsular hematoma; 8 cases showed gross hematuria, 62 cases showed microscopic hematuria, and the rest had no obvious symptoms; (2) the nursing satisfaction rate of 94 cases was as high as 95.7%.

Conclusion

US-PRB is a safe and effective auxiliary examination method, which can improve the success rate of puncture and reduce postoperative complications. Effective nursing can reduce the incidence of postoperative complications and improve patient satisfaction.

Evaluation of percutaneous renal biopsy complications based on outcomes and indicators of the Nursing Outcomes Classification

Objective:

to evaluate the complications of percutaneous renal biopsy based on outcomes and clinical indicators of the Nursing Outcomes Classification.

Method:

a prospective longitudinal study. The sample consisted of 13 patients submitted to percutaneous renal biopsy, with 65 evaluations. The patients were evaluated in five moments in the 24 hours after the procedure, using an instrument developed by the researchers based on five outcomes (Blood coagulation, Circulation status, Blood loss severity, Pain level, Comfort status: Physical) and 11 indicators. The Generalized Estimation Equation Test was used to compare the scores of the indicators. The project was approved by the institutional ethics committee.

Results:

in the 65 evaluations, a statistically significant difference was identified in the reduction of the scores of the following nursing outcomes: Blood coagulation, “hematuria” indicator; Circulation status, in the “systolic blood pressure and diastolic blood pressure” indicators and Comfort status: physical, in the “physical well-being” indicator.

Conclusion:

the evaluated patients did not show major complications. The clinical indicators signaled changes in circulation status, with reduced blood pressure, as well as in blood clotting observed by hematuria, but without hemodynamic instability. The comfort status was affected by the rest time after the procedure.

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.

A Systematic Review of Complications Associated With Percutaneous Native Kidney Biopsies in Adults in Low- and Middle-Income Countries

Introduction

Kidney biopsy is an important tool for making diagnoses and for assessing the drug treatment requirements and disease prognosis in the management of kidney diseases. There are variations in the rate of complications associated with kidney biopsies across countries, and this depends on various clinical and technical factors. The aim of this study is to report on complications associated with kidney biopsy performed in low- and middle-income countries.

Methods

Two reviewers searched studies in MEDLINE, Embase, Cochrane Reviews, and African Journals Online. A random effects meta-analysis method was used to pool estimates of complications.

Results

We identified 39 studies reporting on 19,500 kidney biopsies with overall complications (major + minor) rate of 14.9% (95% confidence interval = 11.4%–18.7%). Fewer complications were reported in biopsies performed with real-time ultrasound scans compared to those pre-marked using ultrasound or blind procedures (12.4% vs. 14.9% vs. 24.5%; P = 0.037), respectively. Complications, albeit lower for procedures performed with automated needles (13.3%), were not significantly different from those performed with nonautomated needles (17.3%; P = 0.588). Major complications included macroscopic hematuria (1.48%), nephrectomy (0.04%), blood loss requiring red cell transfusion (0.24%), angiographic intervention (0.22%), and death (0.01%).

Conclusion

Complications associated with kidney biopsy in low- and middle-income countries are low, are comparable to those in other settings, and occur more sparingly when real-time ultrasound techniques or automated kidney biopsy needles are used. This suggests the need to expand the use of this procedure to improve diagnosis of kidney pathologies and choice of therapy when indicated.

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.

Non-Invasive Imaging for Evaluating Cardiovascular Involvement in Patients with Primary and Lupus Nephritis

Background:

Evidence suggests that proteinuric diseases, such as primary or secondary glomerulonephritis, increase cardiovascular risk, but few studies confirmed this association.

Methods:

This is a cross-sectional, observational study on 32 patients, 17 with Primary Glomerulonephritis (PG) and 15 with Lupus Glomerulonephritis (LG). The control group consisted of 32 healthy individuals. Intima-media thickness (IMT) of the left common carotid artery, carotid bifurcation and internal carotid artery was measured by ultrasound. Left ventricular myocardial deformation was assessed by the use of the Global Circumferential Strain (GCS) and the Global Longitudinal Strain (GLS) following 2-Dimensional (2D) echocardiography in all participants.

Results:

Patients with glomerulonephritis in both groups showed significantly lower GLS compared with controls (p=0.0005). There was also a significant difference in common carotid IMT values between the LG and GP group (0.45±0.09 vs. 0.58±0.17 mm, respectively; p=0.01), but there was no difference with the control group. In patient group (n=32), a significantly positive correlation was observed between C-reactive protein and proteinuria (r=0.98; p<0.0001), whereas negative correlations were found between common carotid IMT and creatinine clearance (r=-0.97; p<0.0001) and between carotid bifurcation IMT and phosphate levels (r=-0.97; p<0.0001)

Conclusion:

Subclinical systolic myocardial dysfunction is present early in the course of glomerular disease. The use of 2D GLS revealed that LG and PG patients with no cardiovascular symptoms or history and a preserved left ventricle ejection fraction on conventional echocardiography had subclinical reduction in LV global longitudinal systolic function compared with controls.

Primary hemostatic function in dogs with acute kidney injury

BACKGROUND

Bleeding tendencies can occur with uremia.

OBJECTIVES

To characterize primary hemostatic function in dogs with acute kidney injury (AKI).

ANIMALS

Ten dogs with International Renal Interest Society AKI grade III or above and 10 healthy controls.

METHODS

Prospective study comparing PCV, platelet count, platelet aggregometry (Multiplate), and von Willebrand factor antigen to collagen binding activity ratio (vWF:Ag:vWF:CBA) in 2 groups of dogs (AKI group versus controls). Buccal mucosal bleeding time was measured in the AKI group only. Data are presented as median [25th, 75th percentile] unless otherwise stated. Significance was set at P < .05.

RESULTS

Mean PCV was significantly lower in the AKI (34.7%; ±SD, 8.8) than in the control (46.1%; ±SD, 3.6; P < .001) group. Platelet count was significantly higher in the AKI (350.5 × 103 /μL [301, 516]) than in the control (241 × 103 /μL [227, 251]; P = .01) group. Collagen-activated platelet aggregometry measured as area under the curve was significantly lower in the AKI (36.9 ± 17.7) than in the control (54.9 ± 11.2; P = .05) group. vWF:Ag:vWF:CBA was significantly higher in the AKI (2.2 [1.9, 2.6]) than in the control (1.1 [1.1, 1.2]; P = .01) group. There was a strong correlation between vWF:Ag:vWF:CBA and creatinine (r = 0.859; P < .001), but no other variables.

CONCLUSIONS AND CLINICAL IMPORTANCE

Dogs with AKI had decreased collagen-activated platelet aggregation and appear to have a type II von Willebrand disease-like phenotype as indicated by the high vWF:Ag:vWF:CBA.

Development of a 2-dimensional atlas of the human kidney with imaging mass cytometry

An incomplete understanding of the biology of the human kidney, including the relative abundances of and interactions between intrinsic and immune cells, has long constrained the development of therapies for kidney disease. The small amount of tissue obtained by renal biopsy has previously limited the ability to use patient samples for discovery purposes. Imaging mass cytometry (IMC) is an ideal technology for quantitative interrogation of scarce samples, permitting concurrent analysis of more than 40 markers on a single tissue section. Using a validated panel of metal-conjugated antibodies designed to confer unique signatures on the structural and infiltrating cells comprising the human kidney, we performed simultaneous multiplexed imaging with IMC in 23 channels on 16 histopathologically normal human samples. We devised a machine-learning pipeline (Kidney-MAPPS) to perform single-cell segmentation, phenotyping, and quantification, thus creating a spatially preserved quantitative atlas of the normal human kidney. These data define selected baseline renal cell types, respective numbers, organization, and variability. We demonstrate the utility of IMC coupled to Kidney-MAPPS to qualitatively and quantitatively distinguish individual cell types and reveal expected as well as potentially novel abnormalities in diseased versus normal tissue. Our studies define a critical baseline data set for future quantitative analysis of human kidney disease.

Direction of the Biopsy Needle in Ultrasound-Guided Renal Biopsy Impacts Specimen Adequacy and Risk of Bleeding

INTRODUCTION

Although medical factors such as hypertension and coagulopathy have been identified that are associated with hemorrhage after renal biopsy, little is known about the role of technical factors. The purpose of our study was to examine the effects of biopsy needle direction on renal biopsy specimen adequacy and bleeding complications.

METHODS

Two hundred and forty-two patients who had undergone ultrasound-guided renal biopsies were included. A printout of the ultrasound picture taken at the time of the biopsy was used to measure the biopsy angle ("angle of attack" [AOA]) and to determine if the biopsy needle was aimed at the upper or lower pole and if the medulla was targeted or avoided.

RESULTS

Of the 3 groups of biopsy angle, an AOA of between 50°-70° yielded the most glomeruli per core (P = .001) and the fewest inadequate specimens (4% vs 15% for > 70°, and 9% for < 50°, P = .038). Biopsy directed at a pole vs an interpolar region resulted in fewer inadequate specimens (8% vs 23%, P = .005), while biopsies that were medulla-avoiding resulted in fewer inadequate specimens (5% vs 16%, P = .004) and markedly reduced bleeding complications (12% vs 46%, P < .001) compared to biopsies where the medulla was entered.

DISCUSSION

An AOA of approximately 60°, aiming at the poles, and avoiding the medulla were each associated with fewer inadequate biopsies and bleeding complications. While biopsy of the medulla is necessary for some diagnoses, the increased bleeding risk emphasizes the need for communication between nephrologist, pathologist, and radiologist.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Multiparametric magnetic resonance imaging of experimental chronic kidney disease: A quantitative correlation study with histology

Objectives

In human chronic kidney disease (CKD) the extent of renal tubulointerstitial fibrosis correlates with progressive loss of renal function. However, fibrosis can so far only be assessed by histology of kidney biopsies. Magnetic resonance imaging (MRI) can provide information about tissue architecture, but its potential to assess fibrosis and inflammation in diseased kidneys remains poorly defined.

Materials and methods

We evaluated excised kidneys in a murine adenine-induced nephropathy model for CKD by MRI and correlated quantitative MRI parameters (T1, T2, and T2* relaxation times, apparent diffusion coefficient and fractional anisotropy) with histological hallmarks of progressive CKD, including renal fibrosis, inflammation, and microvascular rarefaction. Furthermore, we analyzed the effects of paraformaldehyde fixation on MRI parameters by comparing kidney samples before and after fixation with paraformaldehyde.

Results

In diseased kidneys T2 and T2* relaxation times, apparent diffusion coefficient and fractional anisotropy in the renal cortex and/or outer medulla were significantly different from those in control kidneys. In particular, T2 relaxation time was the best parameter to distinguish control and CKD groups and correlated very well with the extent of fibrosis, inflammatory infiltrates, tubular dilation, crystal deposition, and loss of peritubular capillaries and normal tubules in the renal cortex and outer medulla. Fixation with paraformaldehyde had no impact on T2 relaxation time and fractional anisotropy, whereas T1 times significantly decreased and T2* times and apparent diffusion coefficients increased in fixed kidney tissue.

Conclusions

MRI parameters provide a promising approach to quantitatively assess renal fibrosis and inflammation in CKD. Especially T2 relaxation time correlates well with histological features of CKD and is not influenced by paraformaldehyde fixation of kidney samples. Thus, T2 relaxation time might be a candidate parameter for non-invasive assessment of renal fibrosis in human patients.

Vascular rejection in renal transplant: Diagnostic value of contrast-enhanced ultrasound (CEUS) compared to biopsy

BACKGROUND

Despite of the more potent immunosuppressive medication, vascular rejection is still a major issue after renal transplantation. Renal biopsy is the gold standard diagnostic to evaluate acute and chronic allograft rejection. As it is an invasive diagnostic there is the risk of complications like haematoma, arteriovenous fistulas, active bleeding or infection. Contrast-enhanced ultrasound is a non-invasive imaging modality that allows visualising renal transplant perfusion.

OBJECTIVE

To analyse the sensitivity and specificity of contrast-enhanced ultrasound (CEUS) compared to biopsy as gold standard in diagnosing vascular rejection in renal transplant patients.

METHODS

A total of 57 renal transplant recipients with poor renal allograft function with initial diagnostic imaging between 2006 and 2017 were included in the study. Clinical data and imaging studies were analysed retrospectively. The diagnostic accuracy of CEUS in diagnosing vascular rejection of the renal transplant was compared to renal biopsy as gold standard. Out of 57 patients 7 patients showed signs of vascular rejection in biopsy. In 6 out of these 7 patients CEUS described irregularities in renal perfusion suspicious of vascular rejection.

RESULTS

CEUS showed a sensitivity of 85.7%, a specificity of 100%, a positive predictive value (PPV) of 100%, and a negative predictive value (NPV) of 98.0%.

CONCLUSIONS

CEUS is a safe, non-nephrotoxic imaging modality for the initial imaging of renal transplant recipients with elevated kidney function parameters suspicious of vascular rejection. Compared to renal biopsy as gold standard CEUS shows a high specificity and PPV in detecting signs of vascular rejection. Since sub-types of vascular rejection with cellular and humoral components with greater risk for allograft loss have been described renal biopsy is inevitable in these cases.

Incidence of major complications after percutaneous native renal biopsies in adults from low-income to middle-income countries: a protocol for systematic review and meta-analysis

INTRODUCTION

Kidney biopsy is an essential tool for guiding clinicians towards diagnoses, treatment and determining prognosis in renal disease. However, the procedure can be marred by various complications. The reported occurrence of complications varies among countries or regions and is also affected by several clinical and technical factors. This systematic review and meta-analysis aims to evaluate the incidence of major complications after percutaneous native renal biopsy in low-income to middle-income countries (LMICs).

METHODS AND ANALYSIS

We will include studies of populations from LMIC as per World Bank 2017 country list. Relevant abstracts published from 1 January 1980 to 30 December 2017 will be searched in PubMed, Cochrane, Excerpta Medica Database (Embase) and African Journals Online, without language restriction. Two reviewers will independently screen, select studies, extract data and assess the risk of bias in each study. A third reviewer will arbitrate in cases of disagreements. The study-specific estimates will be pooled through a random-effects model meta-analysis to obtain an overall summary estimate of the incidence of major complications across studies. Clinical and statistical heterogeneity will be evaluated by Cochrane's Q statistic. Funnel-plot analysis and Egger's test will be used to assess publication bias. Results will be presented by geographical region and income group.

ETHICS AND DISSEMINATION

This study will use published data. Therefore, there is no requirement for ethical approval. This systematic review and meta-analysis is expected to inform healthcare workers and providers about the occurrence of major complications following renal biopsies and highlight possible actions needed to improve the safety of the procedure in LMICs. The final report will be published as an original article in a peer-reviewed journal. Findings will also be presented at a conference and submitted to relevant health authorities.

PROSPERO REGISTRATION NUMBER

CRD42017077656.

Needle guides enhance tissue adequacy and safety of ultrasound-guided renal biopsies

Background

Needle guides have recently come into use for ultrasound-guided percutaneous renal biopsies; however, it is not yet clear if the use of needle guides leads to decreased post-biopsy complication rates and improved tissue yields. Thus, we conducted a retrospective single center study comparing biopsy yield, adequacy, and rates of complications before and after utilization of a needle guide device.

Methods

A retrospective analysis was performed on all native kidney biopsies performed before and after June 2015 corresponding to the start of needle guide use. All biopsies in the latter period of the study were performed by a single operator. We compared clinical characteristics, indications, type of investigation, tissue yield, adequacy of procedure, and rates of major and minor complications.

Results

A total of 343 biopsies were analyzed, 140 in the pre-needle guide use period (Period I) and 203 in the needle guide use period (Period II). Biopsy yields were similar, irrespective of the use of needle guides. Tissue adequacy was better in Period II (93.7% vs. 84%, P < 0.001, with respect to pathologist-reported inconclusive biopsies. There were no differences in terms of major complications (1.7%) for the two periods; however, the rate of minor complications (8.4%) was significantly reduced in Period II (P = 0.006). According to multiple logistic regression analysis, not using a needle guide (odds ratio, 3.70; P < 0.001) along with low hemoglobin level, higher pre-dialysis serum creatinine level, and high urinary red blood cell count were significant predictors of biopsy complications.

Conclusion

Use of a needle guide improves biopsy adequacy and is associated with reduced rates of minor complications in native renal biopsies. Therefore, needle guides may be recommended in percutaneous renal biopsies, especially when transitioning to single-operator performed procedures.

Biopsy-Free Prediction of Pathologic Type of Primary Nephrotic Syndrome Using a Machine Learning Algorithm

BACKGROUND/AIMS

Renal biopsy is the gold standard to determine the pathologic type of primary nephrotic syndrome, which is critical for diagnosis, choice of treatment and evaluation of prognosis. However, in some cases, renal biopsy cannot be performed.

METHODS

To explore the possibility of predicting the histology type of primary nephrotic syndrome without the need for biopsy, we trained and validated a machine learning algorithm using data from 222 patients with biopsy-confirmed primary nephrotic syndrome treated at our hospital between May 2008 and January 2016. The model was then tested prospectively on another sample of 63 patients with biopsy-confirmed primary nephrotic syndrome.

RESULTS

Overall accuracy of prediction from the retrospective set of 222 patients was 62.2% across all types of nephrotic syndrome. The accuracy of model prediction for the prospectively collected dataset of 63 patients was 61.9%. The algorithm identified 17 of 33 variables as contributing strongly to type of renal pathology.

CONCLUSION

To our knowledge, this is the first such application of machine learning to predict the pathologic type of primary nephrotic syndrome, which may be clinically useful by itself as well as helpful for guiding future efforts at machine learning-based prediction in other disease contexts.

Pediatric renal transplant biopsy with ultrasound guidance: the 'core' essentials

This review provides a comprehensive and practical approach to pediatric percutaneous renal transplant biopsies, highlighting techniques and strategies to optimize adequate sample yield and ensure patient safety. In children with end-stage renal disease, transplantation is the preferred choice of therapy, providing for overall lower long-term morbidity and mortality compared with dialysis. In the ongoing management of renal transplant patients, core tissue sampling via a percutaneous renal biopsy remains the gold standard when transplant dysfunction is suspected. Indications for renal transplant biopsy and techniques/tools for adequate sample yield are discussed. Strategies for common challenges such as poor visualization and renal transplant mobility are addressed. We discuss the clinical signs, techniques and imaging findings for common complications including hematomas, arteriovenous fistulas and pseudoaneurysms. Although the percutaneous renal transplant biopsy procedure is generally safe with rare complications, care must be taken to ensure major complications are promptly recognized and treated. Adequate tissue samples obtained via renal biopsy are imperative to promptly identify transplant rejection to provide valuable information for patient diagnosis, treatment and outcomes. Radiologist and nephrologist attention to proper ultrasound techniques and optimal biopsy tools are critical to ensure tissue adequacy and minimize complications.

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.

Establishing the presence or absence of chronic kidney disease: Uses and limitations of formulas estimating the glomerular filtration rate

The development of formulas estimating glomerular filtration rate (eGFR) from serum creatinine and cystatin C and accounting for certain variables affecting the production rate of these biomarkers, including ethnicity, gender and age, has led to the current scheme of diagnosing and staging chronic kidney disease (CKD), which is based on eGFR values and albuminuria. This scheme has been applied extensively in various populations and has led to the current estimates of prevalence of CKD. In addition, this scheme is applied in clinical studies evaluating the risks of CKD and the efficacy of various interventions directed towards improving its course. Disagreements between creatinine-based and cystatin-based eGFR values and between eGFR values and measured GFR have been reported in various cohorts. These disagreements are the consequence of variations in the rate of production and in factors, other than GFR, affecting the rate of removal of creatinine and cystatin C. The disagreements create limitations for all eGFR formulas developed so far. The main limitations are low sensitivity in detecting early CKD in several subjects, e.g., those with hyperfiltration, and poor prediction of the course of CKD. Research efforts in CKD are currently directed towards identification of biomarkers that are better indices of GFR than the current biomarkers and, particularly, biomarkers of early renal tissue injury.

Vasculitis for the internist: focus on ANCA-associated vasculitis

Vasculitides comprise several diseases affecting vessels of different sizes, mainly arteries, but also capillaries and veins. Antineutrophil cytoplasm antibody-associated vasculitides (AAVs) belong to the systemic necrotizing small-vessel vasculitis group that comprises granulomatosis with polyangiitis, microscopic polyangiitis and eosinophilic granulomatosis with polyangiitis. Internists often see AAV patients, and although their outcomes are usually good, the disease can be responsible for morbidity and mortality. Herein, after reviewing the literature, we concentrate on selected aspects important for the internist, including classification, diagnostic dilemmas, treatment novelties, and follow-up.

Effectiveness and safety of two 18-gauge needle types on native and allograft renal biopsies

Percutaneous biopsy is a key diagnostic tool for both native and allograft kidney diseases. Adequacy criteria vary, but at a minimum, a biopsy should allow the pathologist to reach a diagnosis and provide prognostic information such as the degree of interstitial fibrosis and tubular atrophy (IF/TA) and percentage of glomerulosclerosis. Whereas most studies use glomerular counts as a surrogate for biopsy adequacy, the amount and preservation of tubulointerstitium is equally important, considering IF/TA is a major prognostic parameter for most medical renal diseases. Many studies have compared the diagnostic adequacy of different gauge needles; however few have investigated performance differences between same gauge needles. In this study, we retrospectively analyzed 235 renal biopsies performed at a single center in Canada over 2years to compare the utilization, safety, diagnostic and prognostic performance of two 18-gauge needles in native and allograft kidney biopsies. We found no significant difference in needle utilization between native and allograft kidneys, or between trainees and staff radiologists. The total tissue yielded area, glomerular counts, percentage of inadequate biopsies and number of passes were similar; however the number of cases in which IF/TA evaluation was deemed not possible was higher for biopsies using disposable instrument needles (4.3% vs. 0%; p=0.01). These also showed greater number of tissue fragments (median 4 for reusable vs 3 for disposable; p=0.04). We postulate that the increased tissue fragmentation might have impaired the pathologists ability to accurately assess interstitial fibrosis and tubular atrophy in biopsies obtained with the disposable instrument needles.

Acute Kidney Injury Recognition in Low- and Middle-Income Countries

Acute kidney injury (AKI) is increasingly common around the world. Because of the low availability of effective therapies and resource limitations, early preventive and therapeutic measures are essential to decrease morbidity, mortality, and cost. Timely recognition and diagnosis of AKI requires a heightened degree of suspicion in the appropriate clinical and environmental context. In low- and middle-income countries (LMICs), early detection is impaired by limited resources and low awareness. In this article, we report the consensus recommendations of the 18th Acute Dialysis Quality Initiative meeting in Hyderabad, India, on how to improve recognition of AKI. We expect these recommendations will lead to an earlier and more accurate diagnosis of AKI, and improved research to promote a better understanding of the epidemiology, etiology, and histopathology of AKI in LMICs.

Long-term Response to Nivolumab and Acute Renal Failure in a Patient with Metastatic Papillary Renal Cell Carcinoma and a PD-L1 Tumor Expression Increased with Sunitinib Therapy: A Case Report

INTRODUCTION

Papillary renal cell carcinoma (PRCC), which represents around 20% of renal cell carcinomas, is a heterogeneous disease that includes different tumor types with several clinical and molecular phenotypes. Nivolumab, a fully human IgG4 programed cell death protein 1 immune checkpoint inhibitor antibody, has shown not only an overall survival advantage when compared to everolimus but also a relatively good side-effect profile among patients with previously treated advanced or metastatic renal cell carcinoma.

CASE REPORT

We describe a case of a young man diagnosed with PRCC that achieved a durable response to nivolumab despite a temporary suspension of the treatment due to a renal function side effect. To the best of our knowledge, it is the first renal failure secondary to nivolumab in a metastatic renal cell carcinoma patient.

CONCLUDING REMARKS

Nivolumab is a promising drug in patients with metastatic PRCC and long-term responses can be achieved. In case of acute renal failure secondary to this treatment, temporary therapy suspension and a low dose of systemic corticosteroids can recover renal function without a negative impact on treatment efficacy.