The risks associated with percutaneous native kidney biopsies: a prospective study

Single-Cell Advances in Investigating and Understanding Chronic Kidney Disease and Diabetic Kidney Disease

Chronic kidney disease (CKD) and its subset diabetic kidney disease are progressive conditions that affect >850 million people worldwide. Diabetes, hypertension, and glomerulonephritis are the most common causes of CKD, which is associated with significant patient morbidity and an increased risk of cardiovascular events, such as heart failure, ultimately leading to premature death. Despite newly approved drugs, increasing evidence shows that patients respond to treatment differently given the complexity of disease heterogeneity and complicated pathophysiology. This review article presents an integrative approach to understanding and addressing CKD through the lens of precision medicine and therapeutics. Leveraging advancements in single-cell omics technologies and artificial intelligence, we can explore the intricate cellular mechanisms underlying CKD and diabetic kidney disease pathogenesis. By dissecting the cellular heterogeneity and identifying rare cell populations using single-cell approaches, it will be possible to uncover novel therapeutic targets and biomarkers for personalized treatment strategies. Finally, we discuss the potential of artificial intelligence-driven analyses in predicting disease progression and treatment response, thereby paving the way for tailored interventions.

Urinary N-acetyl-D-glucosaminidase can predict bleeding after a percutaneous kidney biopsy

BACKGROUND

A percutaneous kidney biopsy (PKB) allows nephrologists to make informed decisions for treating various kidney diseases; however, the risk of bleeding complications should be considered, given the vascularity of the kidney. Many studies have reported risk factors for bleeding events after a PKB. However, while urinary N-acetyl-β-D-glucosaminidase (NAG) is a useful biomarker of kidney disease severity, little is known about whether or not urinary NAG is related to the bleeding risk.

METHODS

Medical records of patients who underwent a PKB at the National Defense Medical College Hospital between October 2018 and October 2023 were retrospectively studied. Hemoglobin (Hb) loss ≥ 1 g/dL was defined as a bleeding event.

RESULTS

Of the 213 patients, 110 (51.6%) were men, and the median age was 56 years old (interquartile range 40-71). The most frequent diagnosis on a PKB was IgA nephropathy (N = 72; 34.0%). Fifty-four patients (25.3%) experienced Hb loss ≥ 1 g/dL after a PKB, and urinary NAG/Cr levels before the biopsy were able to predict a bleeding event, with an area under the receiver operating characteristic curve of 0.65 (p = 0.005). Using the optimal cutoff value of 35 U/gCr, urinary NAG/Cr was found to be an independent risk factor by multiple logistic regression analysis (odds ratio 3.21, 95% confidence interval 1.42-7.27, p = 0.005). Even after adjusting for previously-reported risk factors, the elevated urinary NAG/Cr ratio remained a statistically significant variable. Compared with the pathological findings, only the severity of multilayered elastic laminae of the small muscular artery was associated with both urinary NAG/Cr levels (p = 0.008) and bleeding events (p = 0.03).

CONCLUSION

Urinary NAG successfully predicted not only the severity of kidney disorders but also bleeding events after a PKB. Arteriosclerosis in the kidneys may be the mechanism underlying these increased bleeding events.

Sonological predictors of complications of percutaneous renal biopsy-a prospective observational study

Percutaneous renal biopsy, although essential for renal disease diagnosis, is associated with a number of post-biopsy complications ranging from gross haematuria to AV fistula to death. In this study, we carried out an active haematoma surveillance and attempted to correlate renal sonological parameters-kidney length, renal parenchymal changes, renal cortical and parenchymal thickness for their potential use in prediction of post-renal biopsy complications.

METHODS

This was a prospective study done from April 2022 to April 2023 on all adult patients undergoing native or transplant kidney biopsy. Baseline clinical, laboratory and renal sonological parameters were noted prior to biopsy. USG-guided renal biopsy was done and any haematoma at 0 h, 12 h and 24 h post-biopsy noted. Biopsy complications including need for any interventions were noted.

RESULTS

Out of the 240 patients enrolled in the study, 58.3% experienced post-biopsy complications. Among these, 5% of patients encountered major complications, with 3.33% necessitating medical intervention following renal biopsy procedures. A high percentage, 98.89%, exhibited hematoma formation within 12 h post-biopsy. Furthermore, our analysis revealed that a hematoma size exceeding 1.2 cm at the 12-h mark exhibited a sensitivity of 100% and specificity of 71% in predicting the need for blood transfusion. Renal parenchymal changes were the most reliable sonological parameters for predicting post-biopsy complication on multivariate analysis.

CONCLUSION

The incidence of major complications requiring interventions following renal biopsy is notably low. Our study highlights the significance of renal sonological characteristics, including parenchymal thickness, cortical thickness and parenchymal changes, in predicting these complications. Furthermore, we emphasize the utility of hematoma surveillance immediately post-biopsy and at the 12 h, as a valuable tool for predicting the necessity of post-biopsy interventions. This approach can aid in efficiently triaging patients and determining the need for further observation post-renal biopsy.

Membranous nephropathy-diagnosis and identification of target antigens

Membranous nephropathy (MN) is a common cause of nephrotic syndrome in adults. MN is characterized by subepithelial accumulation of immune complexes along the glomerular basement membrane. The immune complexes are composed of immunoglobulin G and a target antigen. PLA2R is the target antigen in approximately 60% of MN cases, and MN is traditionally classified as PLA2R-positive or PLA2R-negative MN. Over the last 7 years, additional target antigens have been identified, which have specific disease associations, distinctive clinical and pathologic findings, and therapeutic implications. The newly discovered target antigens include NELL1, EXT1/EXT2, NCAM1, SEMA3B, PCDH7, FAT1, CNTN1, NTNG1, PCSK6 and NDNF. To group all these antigens into a generic 'PLA2R-negative' MN group is imprecise and un-informative. We propose a logical approach for detection of the target antigen which includes (i) currently available serology-based testing to detect anti-PLA2R and anti-THSD7A antibodies; and (ii) kidney biopsy testing to detect the target antigens. Determination of the antigen on kidney biopsy can be done by immunohistochemistry or immunofluorescence studies. Alternatively, laser capture microdissection (LCM) of glomeruli followed by mass spectrometry (MS) can be used to identify a target antigen. LCM/MS has the advantage of being a one-stop test and is particularly useful for detection of rare target antigens. At the current time, while it is possible to detect the newer antigens by immunohistochemistry/immunofluorescence/LCM/MS, serology-based tests to detect serum antibodies to the new antigens are not yet available. It is critical that serology-based tests should be developed not just for accurate diagnosis, but as a guide for treatment. We review the current methodology and propose an algorithm for diagnosis and detection of target antigens in MN that may shape the current practice in the future. Membranous nephropathy (MN) results from accumulation of subepithelial immune complexes along the glomerular basement membrane.PLA2R is the most common target antigen, but newly discovered target antigens have filled the void of PLA2R-negative MN.MN associated with the newly discovered target antigens have distinctive clinical and pathologic findings, treatment and prognostic implications. These include NELL1, EXT1/EXT2, NCAM1, PCDH7, SEMA3B, CNTN1, FAT1, NDNF and PCSK6.Immunohistochemistry/immunofluorescence methodology is currently in use for detecting target antigens in kidney biopsy tissue, although we anticipate laser capture microdissection of glomeruli followed by mass spectrometry will become available soon.Serologic testing is currently available for only detecting antibodies to PLA2R and THSD7A. It is critical that serologic tests become available for detecting antibodies to the newly discovered antigens.

Kidney Biopsy and Immuno-Rheumatological Diseases: A Retrospective and Observational Study

Renal involvement is a common occurrence in patients with immuno-rheumatological diseases (IRDs). Several instances of glomerulonephritis (GN) occur in the setting of IRD and complicate the clinical course of an underlying condition. The aim of this study was to observe the spectrum of nephropathies according to age, kidney function, history of IRD at the time of biopsy, and histopathological kidney diagnosis. We evaluated data relating to 699 consecutive kidney native biopsies (female 52.1%) with a median age of 48 years (IQR 34-62) performed in adult patients collected over 15 years. The study population was divided into three groups: patients with kidney histological findings correlated to underlying IRD (Group 1), patients with kidney histological findings not correlated to underlying IRD (Group 2), and patients with kidney histological findings compatible with "de novo" IRD (absent in personal medical history) (Group 3). Kidney involvement related to IRD was found in 25.2% of patients. Group 1 was mostly represented by lupus nephritis (76.6%), with a younger age than Group 3 (p < 0.001) and by a higher percentage of females than other groups (p < 0.001). Group 3 was the most represented by microscopic polyangiitis (50.8%) when compared with the other two groups (p < 0.001). Acute nephritic syndrome (p < 0.001), acute kidney injury (AKI), and abnormal urinalysis (p < 0.001) were more represented in Group 3 than the other groups. In conclusion, IRDs are characterized by different clinical presentations and heterogeneous histological findings. Kidney biopsy remains fundamental to achieving the correct diagnosis and starting targeted therapy.

Bleeding complications after percutaneous kidney biopsies - nationwide experience from Brunei Darussalam

BACKGROUND

Kidney biopsy serves as a valuable method for both diagnosing and monitoring kidney conditions. Various studies have identified several risk factors associated with bleeding complications following the procedure, but these findings have shown inconsistency and variation.

AIM

To investigate the risk of bleeding complications following percutaneous kidney biopsy in Brunei Darussalam. We sought to explore the relevant clinical and pathological risk factors associated with these complications while also considering the findings within the broader international literature context.

METHODS

We conducted a retrospective study of all adult patients who underwent kidney biopsy in Brunei Darussalam from October 2013 to September 2020. The outcomes of interest were post-biopsy bleeding and the need for blood transfusions. Demographics, clinical, laboratory and procedural-related data were collected. Logistic regression analysis was used to identify predictors of outcomes.

RESULTS

A total of 255 kidney biopsies were included, with 11% being performed on transplanted kidneys. The majority of biopsies were done under ultrasound guidance (83.1%), with the rest under computer tomography guidance (16.9%). The most common indications for biopsy were chronic kidney disease of undefined cause (36.1%), nephrotic syndrome (24.3%) and acute kidney injury (11%). Rate of bleeding complication was 6.3% - 2% frank hematuria and 4.3% perinephric hematoma. Blood transfusion was required in 2.8% of patients. No patient lost a kidney or died because of the biopsy. Multivariate logistic regression identified baseline hemoglobin [odds ratio (OR): 4.11; 95% confidence interval (95%CI): 1.12-15.1; P = 0.03 for hemoglobin ≤ 11 g/dL vs. > 11 g/dL) and the presence of microscopic hematuria (OR: 5.24; 95%CI: 1.43-19.1; P = 0.01) as independent risk factors for post-biopsy bleeding. Furthermore, low baseline platelet count was identified as the dominant risk factor for requiring post-biopsy transfusions. Specifically, each 10 109/L decrease in baseline platelet count was associated with an 12% increase risk of needing transfusion (OR: 0.88; 95%CI: 0.79-0.98; P = 0.02).

CONCLUSION

Kidney biopsies were generally well-tolerated. The identified risk factors for bleeding and transfusion can help clinicians to better identify patients who may be at increased risk for these outcomes and to provide appropriate monitoring and management.

Glomeruli Count and Arterial Injury in Real-Time Ultrasound-Guided Needle Kidney Biopsy Specimens: Adequacy of Three Approaches for Pig Kidneys

INTRODUCTION

Real-time ultrasound-guided percutaneous kidney biopsy is essential for diagnosis and treatment planning; nonetheless, the optimal puncture approach has yet to be established. In vivo, performing different approaches on the same patient at once is not possible. This study aimed to determine the impact of different approaches on the number of obtained glomeruli and their potential to cause arterial injury using pig kidneys, which are similar to humans.

METHODS

A total of 120 pig kidneys (60 right-sided kidneys and 60 left-sided kidneys) for research were obtained from a slaughterhouse. The specimens were collected from the lower pole on the sagittal plane of the kidney using three different approaches on the same kidney: caudocranial approach, caudal to cranial; craniocaudal approach, cranial to caudal; and vertical approach, through the surface cortex. Five blinded pediatric nephrologists assessed the number of glomeruli and arterial injuries.

RESULTS

Overall, 360 specimens were collected from the kidneys through biopsy using a 16-gauge needle (mean vertical kidney length, 11.2 ± 0.7 cm; mean depth, 3.47 ± 0.23 cm). No significant difference in the incidence of arterial injury was observed between the three approaches (caudocranial vs. craniocaudal vs. vertical approaches: 78% vs. 87% vs. 87%, p = 0.14). In contrast, the vertical approach retrieved significantly more glomeruli than the caudocranial and craniocaudal approaches (caudocranial approach: 7.5 ± 2.8, craniocaudal approach: 7.8 ± 2.7, and vertical approach: 8.9 ± 3.3, p < 0.001).

CONCLUSIONS

Considering its efficacy and safety profile, the vertical approach may be preferred, as more glomeruli can be obtained without increasing the incidence of arterial injury. Although the results cannot be directly extrapolated to humans due to the differences between species, they still offer important insights into the characteristics of each approach.

Rationale and design of a prospective, clinical study of kidney biopsies in people with type 2 diabetes and severely increased albuminuria (the PRIMETIME 2 study)

INTRODUCTION

Diabetic kidney disease is a severe complication of diabetes. The diagnosis is based on clinical characteristics such as persistently elevated albuminuria, hypertension and decline in kidney function, although this definition is not specific to kidney disease caused by diabetes. The only way to establish an accurate diagnosis-diabetic nephropathy-is by performing a kidney biopsy. The histological presentation of diabetic nephropathy can be associated with a heterogeneous range of histological features with many pathophysiological factors involved demonstrating the complexity of the condition. Current treatment strategies aim to slow disease progression and are not specific to the underlying pathological processes.This study will investigate the prevalence of diabetic nephropathy in individuals with type 2 diabetes (T2D) and severely elevated albuminuria. The deep molecular characterisation of the kidney biopsy and biological specimens may pave the way for improved diagnostic accuracy and a better understanding of the pathological processes involved and may also reveal new targets for individualised treatment.

METHODS AND ANALYSIS

In the PRecIsion MEdicine based on kidney TIssue Molecular interrogation in diabetic nEphropathy 2 study, research kidney biopsies will be performed in 300 participants with T2D, urine albumin/creatinine ratio ≥700 mg/g and estimated glomerular filtration ratio >30 mL/min/1.73 m2. Cutting-edge molecular technologies will be applied to the kidney, blood, urine, faeces and saliva samples for comprehensive multi-omics profiling. The associated disease course and clinical outcomes will be assessed by annual follow-up for 20 years.

ETHICS AND DISSEMINATION

The Danish Regional Committee on Health Research Ethics and the Knowledge Center on Data Protection (in the Capital Region of Denmark) have granted approval for the study. The results will be published in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT04916132.

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.

Risk of bleeding after percutaneous native kidney biopsy in patients receiving low-dose aspirin: a single-center retrospective study

BACKGROUND

Although discontinuation of antiplatelet agents at least 5 days before kidney biopsy is commonly recommended, the evidence behind this practice is of low level. Indeed, few non-randomized studies previously showed an equivalent risk of bleeding in patients receiving aspirin therapy.

METHODS

We conducted a single center retrospective study comparing the risk of complications after percutaneous native kidney biopsy in patients who received low-dose aspirin (ASA) within 5 days from biopsy and those who did not. The main outcome was the difference in the incidence of major complications (red blood cell transfusion, need for selective arterial embolization, surgery, nephrectomy). Secondary outcomes included difference in minor complications, comparison between patients who received ASA within 48 h or within 3-5 days, identification of independent factors predictive of major complications.

RESULTS

We analyzed data on 750 patients, of whom 94 received ASA within 5 days from biopsy. There were no significant differences in the proportion of major complications in patients receiving or not receiving ASA (2.59% and 3.19%, respectively, percentage point difference 1%, 95% CI - 3 to 4%, p = 0.74). Groups were also comparable for minor complications; among patients receiving ASA, there were no differences in major bleeding between those who received ASA within 48 h or 3-5 days from biopsy. Significant baseline predictors of major bleeding in our cohort were platelet count lower than 120*10³/microliter, higher diastolic blood pressure and higher blood urea.

CONCLUSIONS

Treatment with low-dose ASA within 5 days from kidney biopsy did not increase the risk of complications after the procedure.

Diagnosis and management of immune checkpoint inhibitor-associated acute kidney injury

Since their introduction into clinical practice a decade ago, immune checkpoint inhibitors (ICIs) have had an overwhelming impact on cancer treatment. Use of these agents in oncology continues to grow; however, the increased use of these agents has been associated with a parallel increase in ICI-associated immune-related adverse events, which can affect virtually any organ, including the kidneys. ICI-associated acute kidney injury (ICI-AKI) occurs in 2-5% of patients treated with ICIs. Its occurrence can have important consequences, including the temporary or permanent discontinuation of ICIs or other concomitant anticancer therapies and the need for prolonged treatment with corticosteroids. Various mechanisms have been proposed to underlie the development of ICI-AKI, including loss of tolerance to self-antigens, reactivation of drug-specific effector T cells, and the production of kidney-specific autoantibodies. ICI-AKI most commonly manifests as acute tubulo-interstitial nephritis on kidney biopsy and generally shows a favourable response to early initiation of corticosteroids, with complete or partial remission achieved in most patients. The evaluation of patients with suspected ICI-AKI requires careful diagnostic work-up and kidney biopsy for patients with moderate-to-severe ICI-AKI to ensure accurate diagnosis and inform appropriate treatment.