The incidence of major hemorrhagic complications after renal biopsies in patients with monoclonal gammopathies

Unraveling monoclonal gammopathy of renal significance: a mini review on kidney complications and clinical insights

Monoclonal gammopathy of renal significance (MGRS) is where kidney injury occurs due to the accumulation or effects of abnormal monoclonal proteins. These proteins, originating from non-cancerous or pre-cancerous plasma cells or B cells, deposit in specific areas of the kidney. Mechanisms contributing to MGRS include high levels of vascular endothelial growth factor secretion, autoantibodies targeting complement components, and targeting specific receptors leading to nephropathy. Kidney lesions in monoclonal gammopathy of renal significance (MGRS) are classified based on the presence of organized or nonorganized deposits, including fibrillar, microtubular, or crystal inclusions. Kidney biopsy is essential for confirming the diagnosis of MGRS by identifying monoclonal immunoglobulin deposits. Immunofluorescence helps determine the class of light and/or heavy chain involved in MGRS. The treatment approach is clone-directed and hence it depends on the presence of B cell clone or plasma cell clone or any detectable monoclonal protein. Chemotherapy targeting plasma cell or B cell malignancies and autologous hematopoietic cell transplantation may be used to manage MGRS. Kidney outcomes in MGRS patients strongly correlate with the hematologic response to chemotherapy.

Monoclonal gammopathy of renal significance from the perspective of nephrologists

Kidney disease is a frequent complication of multiple myeloma and other malignancies associated with monoclonal gammopathies. Additionally, dysproteinemia-related kidney disease can occur independently of overt multiple myeloma or hematologic malignancies. Monoclonal gammopathy of renal significance (MGRS) is a spectrum of disorders in which a monoclonal immunoglobulin produced by a benign or premalignant B-cell or plasma cell clone causes kidney damage. MGRS-associated renal disease manifests in various forms, including immunoglobulin-associated amyloidosis, monoclonal immunoglobulin deposition diseases (light chain, heavy chain, and combined light and heavy chain deposition diseases), proliferative glomerulonephritis with monoclonal immunoglobulin deposits, C3 glomerulopathy with monoclonal gammopathy, and light chain proximal tubulopathy. Although MGRS is a nonmalignant or premalignant hematologic condition, it has significant renal implications that often lead to progressive kidney damage and, eventually, end-stage kidney disease. This review discusses the epidemiology, pathogenesis, and management of MGRS and focuses on the perspective of nephrologists.

Systematic review and meta-analysis of the clinical features of MGRS

BACKGROUND

It is crucial to identify patients with monoclonal gammopathy of renal significance (MGRS) from those without MGRS but with monoclonal gammopathy and concomitant kidney diseases. However, there have been few studies with large sample sizes, and their findings were inconsistent. This study aimed to conduct a meta-analysis of MGRS to describe the general characteristics of MGRS and its predictive factors.

METHODS

Cohort or case-control studies published through December 2022 and related to clinicopathological features of MGRS were retrieved from the PubMed, Cochrane Library, Web of Science, Scopus, and Embase databases. Two researchers searched for studies that met the inclusion criteria. In the univariate analysis, fixed- or random- effects models were used to obtain pooled estimates of the weighted mean difference (WMD) and odds ratio (OR) for risk factors. In the multivariate analysis, the ORs of the independent risk factors from each study were pooled after transforming the original estimates.

RESULTS

The meta-analysis included six studies. Univariate analysis showed that the following variables were statistically significant in MGRS: age (WMD = 1.78, 95%CI 0.21-3.35), hypertension (OR = 0.54, 95%CI 0.4-0.73), diabetes (OR = 0.42, 95%CI 0.29-0.59), albumin (WMD = - 0.26, 95%CI - 0.38--0.14), urinary protein level (WMD = 0.76, 95%CI 0.31-1.2), urinary protein ≥ 1.5 g/d (OR = 1.98, 95%CI 1.46-2.68), lambda-chain value (WMD = 29.02, 95%CI 16.55-41.49), abnormal free light-chain ratio (OR = 4.16, 95%CI 1.65-10.47), bone marrow puncture rate (OR = 5.11, 95% CI 1.31-19.95), and abnormal bone marrow outcome rate (OR = 9.63, 95%CI 1.98-46.88). Multivariate analysis showed urinary protein ≥ 1.5 g/d (OR = 2.80, 95%CI 1.53-5.15) and an abnormal free light-chain ratio (OR = 6.98, 95%CI 4.10-11.91) were associated with predictors of MGRS.

CONCLUSIONS

Compared with non-MGRS patients with monoclonal gammopathy and concomitant kidney diseases, patients with MGRS were older, had fewer underlying diseases, more urinary protein, more abnormal free light-chain ratio, and more abnormal bone marrow results. Urinary protein ≥ 1.5 g/d and an abnormal free light-chain ratio were independent risk factors for MGRS.

Assessment of current clinical practice throughout the UK for the diagnosis and management of monoclonal gammopathy of renal significance

Since the inception of the term monoclonal gammopathy of renal significance (MGRS) in 2012 by the International Kidney and Monoclonal Gammopathy Research Group, there have been no consensus guidelines specifically pertaining to the UK regarding to patient management. We aimed to identify both regional and cross-discipline variation in current clinical practice, to provide insight and rationale for a potential standardised pathway in the future. A national survey of 88 consultants from the disciplines of haematology and nephrology was conducted between June 2020 and July 2021. Agreement was evident for aspects of the diagnostic pathway, including presenting features likely to raise suspicion of MGRS and the most pertinent confounding factors to consider before renal biopsy. However, significant variability was identified in both the cohort of diagnostic tests used, as well as urinary work-up for patients with suspected MGRS. Treatment and monitoring frequency was also an aspect of management identified as variable. Despite differences in clinical practice across the UK, MGRS diagnosis was widely regarded to be the joint responsibility of both disciplines. The results provide an indication of inter-regional and interdisciplinary differences in practice, highlighting the need for improved awareness and standardised protocol for management of MGRS that applies to the UK population.

A Case Report of Premalignant Plasma Cell Dyscrasia-Induced Renal Failure in a 31-Year-Old Female

Monoclonal gammopathy of renal significance (MGRS) is a rare disorder in which monoclonal immunoglobulin secreted by nonmalignant B cell or plasma cell clone causes kidney damage. Although MGRS is a premalignant condition, it can cause severe kidney disease and end-stage renal disease (ESRD) at any age. Herein, we present a 31-year-old female with past medical history of lupus nephritis who presented with signs of volume overload and worsening renal function despite adequate immunosuppressive therapy. Renal biopsy revealed heavy and light chain deposition consistent with MGRS. This case report demonstrates the importance of including MGRS in the differential diagnosis of worsening renal function despite adequate treatment, raising awareness of this premalignant yet morbid condition.

Light Chain Cast Nephropathy in Multiple Myeloma: Prevalence, Impact and Management Challenges

“Cast nephropathy” (CN) is a pathological feature of myeloma kidney, also seen to a lesser extent in the context of severe nephrotic syndrome from non-haematological diseases. The name relates to obstruction of distal tubules by “casts” of luminal proteins concentrated by intensive water reabsorption resulting from dehydration or high-dose diuretics. Filtered proteins form complexes with endogenous tubular Tamm-Horsfall glycoprotein. The resulting gel further slows or stops luminal flow upon complete obstruction of distal convoluted tubules and collecting ducts. Thus, a tubular obstructive form of acute kidney injury (AKI) is a common consequence of CN. The pathogenesis of CN will be reviewed in light of recent advances in the understanding of monoclonal disorders of B lymphocytes, leading to the release of immunoglobulin components (free light chains, FLC) into the bloodstream and their filtration across the glomerular basement membrane. Treatment aiming at reduction of the circulating burden of FLC may help recovery of renal function in a fraction of these patients, besides filling the void between the onset of AKI, histopathological diagnosis, and full response to pharmacologic treatment.

Point your SmartPhone at the code above. If you have a QR code reader the video abstract will appear. Or use:

https://youtu.be/-LOd4bqJsIo

Kidney Biopsy in Patients With Monoclonal Gammopathy: A Multicenter Retrospective Cohort Study

Objectives: To analyze the clinical characteristics and renal pathological manifestations of patients with monoclonal gammopathy (MG) and kidney injury. Methods: This was a multicenter retrospective cohort study conducted at four tertiary hospitals in China. The study population comprised patients with MG admitted from January 1 2013 to December 31 2020. Hospitalization records, laboratory data, and kidney biopsy reports of all patients were collected from the electronic hospital information systems. The study outcomes included kidney disease progression and major hemorrhagic complications after kidney biopsy. Results: We identified 1,164 patients with MG, 782 (67.2%) of whom had underlying kidney injury. Of 101 patients who underwent kidney biopsy, 16 had malignant neoplasms. Amyloid nephropathy was the most common finding (n = 34, 33.7%), followed by membranous nephropathy (n = 18, 17.8%) and membranoproliferative nephritis (n = 8, 7.9%). Among 85 patients with non-malignant hematologic conditions who underwent kidney biopsy, 43 had MG of renal significance (MGRS) related lesions and 42 had MG-unrelated lesions. The risk of kidney disease progression was higher in patients with kidney injury than in patients without kidney injury. Conclusion: Among patients with MG and kidney injury, only 12.9% underwent kidney biopsy and more than 40% of these patients had MG-unrelated lesions. A kidney biopsy is safe and essential to maximize the possibility of correct diagnosis for patients with clinically suspected MG of renal significance (MGRS).

Management of acute kidney injury in symptomatic multiple myeloma

Symptomatic multiple myeloma is commonly complicated by acute kidney injury through various mechanisms. The most frequent is the precipitation of monoclonal free light chains with uromodulin in the distal tubules, defining light chain cast nephropathy. Early diagnosis and identification of the cause of acute kidney injury are required for optimizing management and avoiding chronic kidney injury that strongly affects quality of life and patient survival. In light chain cast nephropathy, often manifesting with severe acute kidney injury, renal recovery requires urgent intervention based on vigorous rehydration, correction of precipitating factors, and efficient anti-plasma cell chemotherapy to rapidly reduce the secretion of nephrotoxic free light chains. Currently, the association of the proteasome inhibitor bortezomib with high-dose dexamethasone is the standard regimen in newly diagnosed patients. The addition of another drug such as cyclophosphamide or an immunodulatory agent may improve free light chain response but raises tolerance concerns in frail patients. Further studies are warranted to confirm the role of anti-CD38 monoclonal antibodies, whose efficacy and tolerance have been documented in patients without renal impairment. Despite controversial results from randomized studies, recent data suggest that in patients with light chain cast nephropathy and acute kidney injury requiring dialysis, the combination of chemotherapy with free light chain removal through high-cutoff hemodialysis may increase renal response recovery rates. Kidney biopsy may be helpful in guiding management and assessing renal prognosis that appears to depend on the extent of cast formation and interstitial fibrosis/tubular atrophy. Because of continuous improvement in life expectancy of patients with multiple myeloma, renal transplantation is likely to be increasingly considered in selected candidates.

A non-invasive differential diagnostic model for light chain cast nephropathy in newly diagnosed multiple myeloma patients with renal involvement: a multicenter study

OBJECTIVE

Light chain cast nephropathy is the most common form of renal lesion in multiple myeloma. Kidney impairment caused by light chain cast nephropathy can be reversed and survival can be improved if early diagnosis is available. It is thus of imperative importance to develop a non-invasive method to diagnose light chain cast nephropathy once the kidney biopsy is not always applicable.

METHODS

We consecutively screened newly diagnosed multiple myeloma patients with kidney biopsies from 4 centers in China. Kidney pathologies were reviewed and clinical presentations were recorded. Then a diagnostic model was established by logistic regression and the predictive values were assessed.

RESULTS

Between 1 June 1999 and 30 June 2019, a kidney biopsy was performed in 94 patients with newly diagnosed multiple myeloma, and light chain cast nephropathy was the most common pattern, seen in 52% of biopsied patients. The diagnostic model was established by multivariate logistic regression analysis as P(z) = 1/(1 + e^-z) and z = - 0.093 Hemoglobin (g/L) + 0.421 Serum albumin (g/L) + 3.463 Acute kidney injury (0/1) - 9.207 High-density lipoprotein (mmol/L). If P(z) ≥ 0.55, the diagnosis pointed to light chain cast nephropathy; if P(z) < 0.55, the diagnosis favored non-light chain cast nephropathy. The area under the receiver operating characteristic curves was 0.981 (95% CI 0.959, 1.000). The model had a sensitivity of 93.9%, a specificity of 95.6%, a positive predictive value of 96.0%, a negative predictive value of 94.0%, and a total consistency of 95.0%.

CONCLUSION

We built a novel, non-invasive diagnostic model through a multicenter study, which may be helpful in the diagnosis of light chain cast nephropathy in newly diagnosed multiple myeloma patients.

KDIGO Controversies Conference on onco-nephrology: kidney disease in hematological malignancies and the burden of cancer after kidney transplantation

The bidirectional relationship between cancer and chronic kidney disease (CKD) is complex. Patients with cancer, particularly those with hematological malignancies such as multiple myeloma and lymphoma, are at increased risk of developing acute kidney injury and CKD. On the other hand, emerging evidence from large observational registry analyses have consistently shown that cancer risk is increased by at least 2- to 3-fold in kidney transplant recipients, and the observed increased risk occurs not only in those who have received kidney transplants but also in those on dialysis and with mild- to moderate-stage CKD. The interactions between cancer and CKD have raised major therapeutic and clinical challenges in the management of these patients. Given the magnitude of the problem and uncertainties, and current controversies within the existing evidence, Kidney Disease: Improving Global Outcomes (KDIGO) assembled a global panel of multidisciplinary clinical and scientific expertise for a controversies conference on onco-nephrology to identify key management issues in nephrology relevant to patients with malignancy. This report covers the discussed controversies in kidney disease in hematological malignancies, as well as cancer after kidney transplantation. An overview of future research priorities is also discussed.

[Monoclonal gammopathy of renal significance: consensus of hematologists and nephrologists of Russia on the establishment of nosology, diagnostic approach and rationale for clone specific treatment]

Monoclonal gammopathy of renal significance (MGRS) is a new nosology in modern nephrology and oncohematology. MGRS is defined as kidney injury due to nephrotoxic monoclonal immunoglobulin produced by the B-cell line clone which does not reach the hematological criteria for specific treatment initiation. Monoclonal proteins pathological effects on kidney parenchyma result in irreversible decline of kidney function till the end stage renal disease that in line with the position of International Consensus of hematologists and nephrologists determinates critical necessity for clone specific treatment in patients with MGRS despite the absence of hematological indications for treatment initiation. Main challenge of MGRS in Russian Federation is an inaccessibility of an in-time diagnostic and appropriate treatment for the great majority of patients due to the following reasons: 1) limited knowledge about the MGRS among hematologists and nephrologists; 2) lack of necessary diagnostic resources in most health-care facilities; 3) lack of approved clinical recommendations and medical economic standards for treatment of this pathological entity. Consensus document comprises the opinion of experts leading nephrologists and hematologists of Russian Federation on the problem of MGRS including the incoherence in nosology classification, diagnostics approach and rationale for clone specific treatment. Consensus document is based on conclusions and agreements reached during the conference of leading nephrologists and hematologists of Russia which was held in the framework of symposia Plasma cell dyscrasias and lymphoproliferative diseases: modern approaches to therapy, 1516 of March 2019, Pavlov First Saint Petersburg State Medical University. The present Consensus is intended to define the principal practical steps to resolve the problem of MGRS in Russian Federation that are summarized as final clauses.

Pathophysiology and management of monoclonal gammopathy of renal significance

Recent years have witnessed a rapid growth in our understanding of the pathogenic property of monoclonal proteins. It is evident that some of these small monoclonal proteins are capable of inducing end-organ damage as a result of their intrinsic physicochemical properties. Hence, an umbrella term, monoclonal gammopathy of clinical significance (MGCS), has been coined to include myriad conditions attributed to these pathogenic proteins. Because kidneys are the most commonly affected organ (but skin, peripheral nerves, and heart can also be involved), we discuss MGRS exclusively in this review. Mechanisms of renal damage may involve direct or indirect effects. Renal biopsy is mandatory and demonstration of monoclonal immunoglobulin in kidney, along with the corresponding immunoglobulin in serum or urine, is key to establish the diagnosis. Pitfalls exist at each diagnostic step, and a high degree of clinical suspicion is required to diagnose MGRS. Recognition of MGRS by hematologists and nephrologists is important, because timely clone-directed therapy improves renal outcomes. Autologous stem cell transplant may benefit selected patients.

Clinicopathologic predictors of renal outcomes in light chain cast nephropathy: a multicenter retrospective study

Light chain cast nephropathy (LCCN) in multiple myeloma often leads to severe and poorly reversible acute kidney injury. Severe renal impairment influences the allocation of chemotherapy and its tolerability; it also affects patient survival. Whether renal biopsy findings add to the clinical assessment in predicting renal and patient outcomes in LCCN is uncertain. We retrospectively reviewed clinical presentation, chemotherapy regimens, hematologic response, and renal and patient outcomes in 178 patients with biopsy-proven LCCN from 10 centers in Europe and North America. A detailed pathology review, including assessment of the extent of cast formation, was performed to study correlations with initial presentation and outcomes. Patients presented with a mean estimated glomerular filtration rate (eGFR) of 13 ± 11 mL/min/1.73 m2, and 82% had stage 3 acute kidney injury. The mean number of casts was 3.2/mm2 in the cortex. Tubulointerstitial lesions were frequent: acute tubular injury (94%), tubulitis (82%), tubular rupture (62%), giant cell reaction (60%), and cortical and medullary inflammation (95% and 75%, respectively). Medullary inflammation, giant cell reaction, and the extent of cast formation correlated with eGFR value at LCCN diagnosis. During a median follow-up of 22 months, mean eGFR increased to 43 ± 30 mL/min/1.73 m2. Age, β2-microglobulin, best hematologic response, number of cortical casts per square millimeter, and degree of interstitial fibrosis/tubular atrophy (IFTA) were independently associated with a higher eGFR during follow-up. This eGFR value correlated with overall survival, independently of the hematologic response. This study shows that extent of cast formation and IFTA in LCCN predicts the quality of renal response, which, in turn, is associated with overall survival.

Underlying IgM heavy chain amyloidosis in treatment-refractory IgA nephropathy: A case report

BACKGROUND

Monoclonal immunoglobulin can cause renal damage, with a wide spectrum of pathological changes and clinical manifestations without hematological evidence of malignancy. These disorders can be missed, especially when combined with other kidney diseases.

CASE SUMMARY

A 61-year-old woman presented with moderate proteinuria with normal renal function. She was diagnosed with IgA nephropathy combined with monoclonal gammopathy of undetermined significance after the first renal biopsy. Although having received immunosuppressive treatment for 3 years, the patient developed nephrotic syndrome. Repeated renal biopsy and laser microdissection/mass spectrometry analysis confirmed heavy chain amyloidosis. After nine cycles of bortezomib, cyclophosphamide and dexamethasone, she achieved very good partial hematological and kidney responses.

CONCLUSION

Renal injury should be monitored closely in monoclonal gammopathy patients without obvious hematological malignancy, especially in patients with other pre-existing renal diseases.

Percutaneous Kidney Biopsy and the Utilization of Blood Transfusion and Renal Angiography Among Hospitalized Adults

Introduction

Data on percutaneous kidney biopsy (KBx) incidence and frequencies of hemorrhagic complications among inpatients are limited.

Methods

Using nationally representative US hospitalization discharge data, we report temporal trends in inpatient KBx rates from 2007 to 2014 and estimate frequencies of, and risk factors for, utilization of packed red blood cell (pRBC) transfusion and renal angiography.

Results

From 2007 to 2014, rates of native KBx among adult inpatients increased from 8.2 to 10.0 per 100,000, while transplant KBx rates declined from 3.6 to 3.1 per 100,000. We studied 35,183 and 14,266 discharge records with native and transplant KBx. We found that 5.7% (95% confidence interval [CI]: 5.3%–6.0%) of inpatients undergoing native KBx and 4.9% (4.2%–5.5%) of those undergoing transplant KBx received a pRBC transfusion within 2 days of biopsy. Similarly, 0.6% (0.5%–0.7%) of inpatients undergoing native KBx and 0.4% (0.2%–0.5%) undergoing transplant KBx received a renal angiogram within 2 days of KBx. For inpatient native KBx, female sex, older age, higher chronic kidney disease stage, acute renal failure, lupus, vasculitis, cirrhosis, multiple myeloma/paraproteinemia, and anemia of chronic disease were independently associated with increased odds of pRBC transfusion; cirrhosis and end-stage renal disease (ESRD) were associated with increased odds, and nephrotic syndrome was associated with decreased odds, of renal angiography.

Conclusions

In this large population-based study of inpatient KBx practices, we demonstrate increasing rates of inpatient native KBx among US adults and provide accurate estimates of the frequencies of, and risk factors for, pRBC transfusion and renal angiography following inpatient KBx.

KIDNEY DISEASE ASSOCIATED WITH MONOCLONAL GAMMOPATHIES: SINGLE-CENTER STUDY

INTRODUCTION:Renal injury associated with monoclonal gammopathies (MG) is an area of interest of practical onconephrology. Prevalence, spectrum and renal outcome as far as approaches to treatment in this pathological entity, particularly in Russian population, still remain unclear and need refinement. AIM: Analysis of the prevalence, spectrum, treatment approaches and renal outcome in kidney injury associated with monoclonal gammopathies (MG).

PATIENTS AND METHODS:Patients with MG and renal injury proven by kidney biopsies from 01.01.2011 till 01.05.2018 were enrolled into this one-center prospective study (n=119). Cases of MG of undetermined significance and non-amyloid kidney lesions were estimated as MG of renal significance (MGRS). Treatment approaches, haematological and renal responses were analysed. Worsening of kidney function was estimated as eGFR decrease >25 % from initial value or initiation of renal replacement treatment (RRT), improving – as eGFR increase >25 % from the initial value or the discontinuation of RRT. Other cases were determined as stable kidney function. Kidney outcome was determined in RRT initiation or eGFR<15 ml/min/1,73m2 at the end of follow-up. Long-term kidney outcome was estimated by Kaplan-Meier survival analysis. The median follow-up period was 12 (2; 27) months.

RESULTS.Prevalence of kidney injury associated with MG among all performed kidney biopsies was 7,5 %, MGRS – 0,94 %. Multiple myeloma (MM), AL-amyloidosis and lymphoproliferative disorder (LPD) were diagnosed in 39, 55 and 10 patients, respectively. Prevalence of kidney injury types was the following: Al-amyloidosis (53 %); cast nephropathy (12 %); light chain deposition disease (12 %); C3-glomerulopathy (3 %); proliferative glomerulonephritis (GN) with monoclonal immunoglobulin deposits (3 %); cryoglobulinemic GN (2 %); thrombotic microangiopathy (2 %); podocytopathy (2 %); acute tubular necrosis – 2 %; immunotactoid GN (1 %); fibrillary GN (1 %); proximal tubulopathy (1 %), combination of different types (6 %). Patients mostly were treated with bortezomib and dexamethasone. Autologous stem cell transplantation was performed in 13 patients. Haematological response was achieved in 48,8 %, 45,4 % and 46,7 % of patients with MM, AL-amyloidosis and MGRS, respectively. Worsening of kidney function was registered in 11,1 % of MM and in 37,2 % of AL-amyloidosis; improving or stable kidney function was in 88,9 % and 62,7 % MM and AL-amyloidosis patients, respectively. In MGRS improving (20 %) and stable kidney function (80 %) were detected. Four-years cumulative renal survival in MM, AL-amyloidosis, MGRS and LPD groups was 63 %, 54 %, 80 % and 39 %, respectively, and does not differ between 4 groups.

CONCLUSION:MG-associated kidney disease represented by diverse clinical and morphological patterns is standard problem in routine clinical practice. It is associated with inferior renal outcome and requires a practical implementation of highly-specialized interdisciplinary approach to diagnostics and treatment.

Secondary, AA, Amyloidosis

Secondary, AA, amyloidosis is a rare systemic complication that can develop in any long-term inflammatory disorder, and is characterized by the extracellular deposition of fibrils derived from serum amyloid A (SAA) protein. SAA is an acute-phase reactant synthetized largely by hepatocytes under the transcriptional regulation of proinflammatory cytokines. The kidney is the major involved organ with proteinuria as first clinical manifestation; renal biopsy is the commonest diagnostic investigation. Targeted anti-inflammatory treatment promotes normalization of circulating SAA levels preventing amyloid deposition and renal damage. Novel therapies aimed at promoting clearance of existing amyloid deposits soon may be an effective treatment approach.

Myeloma light chain cast nephropathy, a review

Multiple Myeloma is a plasma cell proliferative disorder that commonly involves the kidney. Renal impairment is a serious complication during the course of the disease that is associated with increased morbidity and mortality. Light chain cast nephropathy is the predominant pattern of renal injury in Multiple Myeloma. This review article focuses on the pathophysiology and diagnostic approach of myeloma cast nephropathy. The management of precipitating factors as well as anti-plasma cell treatment modalities in the context of renal impairment are also discussed.

The treatment of paraprotein-related kidney disease

PURPOSE OF REVIEW

Myeloma kidney and amyloid light-chain (AL) amyloidosis remain the principal kidney complications of paraproteins. In this review, we update readers to many of the recent advances which have occurred in the care and outcomes for patients with these presentations.

RECENT FINDINGS

Myeloma kidney has historically caused a severe acute kidney injury with very poor outcomes. The combination of new diagnostic techniques, enabling a rapid diagnosis and novel chemotherapy agents has transformed these poor outcomes for the better. Two multicentre randomized controlled trials have recently evaluated if the removal of free light chains by high cut-off haemodialysis improves renal outcomes beyond effective chemotherapy alone. Although we await the full articles of these studies to be published, abstracts suggested the studies will have contradictory primary results. In the field of AL amyloidosis, there are now novel criteria for the risk stratification of kidney outcomes which can be used in combination with markers of early kidney response to provide clinicians with powerful tools to guide patient discussions.

SUMMARY

Across both AL amyloidosis and myeloma kidney patient outcomes continue to improve. Principally this improvement has been driven by the continuing development of novel chemotherapy agents in this field.

Paraprotein-Related Kidney Disease: Diagnosing and Treating Monoclonal Gammopathy of Renal Significance

Paraprotein-related kidney disease represents a complex group of diseases caused by an abnormal paraprotein secreted by a clone of B cells. The disease manifestations range from tubulopathies, such as the Fanconi syndrome, to a spectrum of glomerular diseases that can present with varying degrees of proteinuria and renal dysfunction. Diagnosis of these diseases can be challenging because of the wide range of manifestations as well as the relatively common finding of a serum paraprotein, especially in elderly patients. Thus, renal biopsy along with detailed hematologic workup is essential to link the presence of the paraprotein to the associated renal disease. Recent advances in treatment with more effective and targeted chemotherapies, as well as stem cell transplantation, have improved the renal and overall prognosis for many of these disorders.

Paraprotein-Related Kidney Disease: Evaluation and Treatment of Myeloma Cast Nephropathy

Nearly 50% of patients with multiple myeloma develop renal disease, most commonly from AKI caused by cast nephropathy. Development of AKI is associated with poor 1-year survival and reduces the therapeutic options available to patients. There is a great need for more effective therapies. Cast nephropathy is caused by the interaction and aggregation of filtered free light chains and Tamm-Horsfall protein causing intratubular obstruction and damage. The key to treating cast nephropathy is rapid lowering of free light chains, because this correlates with renal recovery. Newer chemotherapy agents rapidly lower free light chains and have been referred to as renoprotective. There is additional great interest in using extracorporeal therapies to remove serum free light chains. Small trials initially showed benefit of therapeutic plasma exchange to improve renal outcomes in cast nephropathy, but a large randomized trial of therapeutic plasma exchange failed to show benefit. A newer technique is extended high-cutoff hemodialysis. This modality uses a high molecular weight cutoff filter to remove free light chains. To date, trials of high-cutoff hemodialysis use in patients with cast nephropathy have been encouraging. However, there are no randomized trials showing the benefit of high-cutoff hemodialysis when used in addition to newer chemotherapeutic regimens. Until these studies are available, high-cutoff hemodialysis cannot be recommended as standard of care.

The Native Kidney Biopsy: Update and Evidence for Best Practice

The kidney biopsy is the gold standard in the diagnosis and management of many diseases. Since its introduction in the 1950s, advancements have been made in biopsy technique to improve diagnostic yield while minimizing complications. Here, we review kidney biopsy indications, techniques, and complications in the modern era. We also discuss patient populations in whom special consideration must be given when considering a kidney biopsy and the important role that the kidney biopsy plays in nephrology training. These data are presented to develop best practice strategies for this essential procedure.

Prognostic value of kidney biopsy in myeloma cast nephropathy: a retrospective study of 70 patients

BACKGROUND

Light chain myeloma cast nephropathy (MCN) is the major cause of renal failure in multiple myeloma and strongly impacts patient survival. The role of kidney biopsy in the management of MCN is unclear.

METHODS

Renal pathological findings were retrospectively studied in 70 patients with multiple myeloma and MCN. Patients were categorized according to the achievement or not of renal response, as defined by estimated glomerular filtration rate (eGFR) ≥ 30 mL/min/1.73 m(2) and/or dialysis independence at 3 months.

RESULTS

Thirty-two patients (46%) achieved a renal response. In the whole study population, the following parameters differed significantly between patients with and without renal response, respectively: baseline median eGFR (13.3 versus 9.3 mL/min/1.73 m(2), P = 0.017), Acute Kidney Injury Network Stage 3 (68.8 versus 92.1%, P = 0.019), haematological response rate (94 versus 34%, P < 0.0001), median percentage of free light chain (FLC) reduction at Day 21 (92 versus 24%, P = 0.006) and median number of casts/10 fields (14 versus 25, P = 0.005). The extent of interstitial fibrosis and tubular atrophy was similar. In multivariate analysis, only FLC reduction at Day 21 was significantly associated with renal response. However, when considering only the subgroup of haematological responders, both median number of casts [odds ratio (OR) = 0.93, 95% confidence interval (95% CI): 0.88-0.98, P = 0.01] and extent of tubular atrophy (OR = 0.03, 95% CI: 0.00-0.52, P = 0.02) were independent predictors of renal response.

CONCLUSIONS

In MCN, the presence of numerous casts and diffuse tubular atrophy is associated with poor renal prognosis. These data suggest that additional strategies to reduce FLC burden should be considered in patients with extensive cast formation.

Diagnosis of monoclonal gammopathy of renal significance

Monoclonal gammopathy of renal significance (MGRS) regroups all renal disorders caused by a monoclonal immunoglobulin (MIg) secreted by a nonmalignant B-cell clone. By definition, patients with MGRS do not meet the criteria for overt multiple myeloma/B-cell proliferation, and the hematologic disorder is generally consistent with monoclonal gammopathy of undetermined significance (MGUS). However, MGRS is associated with high morbidity due to the severity of renal and sometimes systemic lesions induced by the MIg. Early recognition is crucial, as suppression of MIg secretion by chemotherapy often improves outcomes. The spectrum of renal diseases in MGRS is wide, including old entities such as AL amyloidosis and newly described lesions, particularly proliferative glomerulonephritis with monoclonal Ig deposits and C3 glomerulopathy with monoclonal gammopathy. Kidney biopsy is indicated in most cases to determine the exact lesion associated with MGRS and evaluate its severity. Diagnosis requires integration of morphologic alterations by light microscopy, immunofluorescence (IF), electron microscopy, and in some cases by IF staining for Ig isotypes, immunoelectron microscopy, and proteomic analysis. Complete hematologic workup with serum and urine protein electrophoresis, immunofixation, and serum-free light-chain assay is required. This review addresses the pathologic and clinical features of MGRS lesions, indications of renal biopsy, and a proposed algorithm for the hematologic workup.

Factors that can minimize bleeding complications after renal biopsy

Renal biopsy is a very important diagnostic tool in the evaluation of renal diseases. However, bleeding remains to be one of the most serious complications in this procedure. Many new techniques have been improved to make it safer. The risk factors and predictors of bleeding after percutaneous renal biopsy have been extensively reported in many literatures, and generally speaking, the common risk factors for renal biopsy complications focus on hypertension, high serum creatinine, bleeding diatheses, amyloidosis, advanced age, gender and so on. Our primary purpose of this review is to summarize current measures in recent years literature aiming at minimizing the bleeding complication after the renal biopsy, including the drug application before and after renal biopsy, operation details in percutaneous renal biopsies, nursing and close monitoring after the biopsy and other kinds of biopsy methods.

Relationship between hospital volume and hemorrhagic complication after percutaneous renal biopsy: results from the Japanese diagnosis procedure combination database

BACKGROUND

Although hemorrhagic complications are major complications of percutaneous renal biopsy (PRB), the relationship between procedure volume and morbidity remains unclear for PRB. The present study investigated the impact of hospital volume on the occurrence of hemorrhagic complications after PRB.

METHODS

Using large claims-based data in the diagnosis procedure combination database in Japan, we identified inpatients with renal disorders who underwent PRB within 4 days after admission during July to December 2007 to 2010. We assessed patient age, sex, clinical syndromes, hemorrhagic complications and diagnoses, and annual hospital volume of PRB divided into quintiles. Multivariate logistic regression analyses fitted with a generalized estimation equation were performed accounting for within-hospital clustering.

RESULTS

A total of 15,191 patients were identified from 942 hospitals. The overall proportion of hemorrhagic complications was 2.1 %, including diagnoses of hemorrhagic events (1.6 %), red blood cell transfusion (0.5 %), and requiring angiography or endovascular procedure (0.1 %). In-hospital deaths attributable to the complications occurred in 0.06 % of the patients. Patients with rapidly progressive nephritic syndrome (odds ratio 3.41, 95 % confidence interval 2.22-5.25) had significantly higher incidence than those with chronic nephritic syndrome. No significant association was observed between hospital volume and hemorrhagic complications, with odds ratios for the low-intermediate, intermediate, intermediate-high, and high-volume groups relative to the low-volume group of 0.74 (0.43-1.26), 1.19 (0.74-1.92), 1.16 (0.67-2.00), and 1.35 (0.78-2.34), respectively.

CONCLUSIONS

No significant relationship was observed between hemorrhagic complication incidence and hospital volume regarding PRB.

Pathophysiology and treatment of systemic amyloidosis

Amyloid is an abnormal extracellular fibrillar protein deposit in the tissues. In humans, more than 25 different proteins can adopt a fibrillar conformation in vivo that results in the pathognomonic tinctorial property of amyloid (that is, green birefringence when an affected tissue specimen is stained with Congo red dye and viewed by microscopy under cross-polarized light). Amyloid deposition is associated with disturbance of organ function and causes a wide variety of clinical syndromes that are classified according to the respective fibril protein precursor. Systemic amyloidosis, in which amyloid deposits are widespread and typically accumulate gradually, continues to be fatal and is responsible for about one in 1,500 deaths per year in the UK. Advances in our understanding of the pathogenesis of systemic amyloidosis have resulted in the identification of new therapeutic targets, and several drugs with novel mechanisms of action are currently under development. Meanwhile, an increased awareness of amyloidosis coupled with enhancements to existing diagnostic techniques and therapeutic strategies have already resulted in better outcomes for patients with the disease.

Abnormal coagulation tests before kidney biopsies-what next?

Introduction

Bleeding is one of the most feared risks from a renal biopsy. To determine this risk, a clotting screen is performed prior to the biopsy to identify any coagulation abnormalities. In addition, concerns exist with respect to bleeding from platelet dysfunction and the special cases of paraprotenemia.

Method

Literature search of all the relevant articles in relation to bleeding risk from clotting abnormalities and platelet dysfunction in the setting of kidney biopsy was conducted.

Results

Bleeding risk from abnormal clotting screen is minimal in the absence of prior bleeding history in patients with renal disease. Administration of fresh frozen plasma in these cases is probably unnecessary and often causes delay in the procedure. In a similar way, platelet transfusions may not be appropriate in those with platelet dysfunction.

Conclusions

Global coagulation function tests are now available which need to be considered to determine bleeding risk before kidney biopsy, in conjunction with a good patient history.

Urinary albumin excretion patterns of patients with cast nephropathy and other monoclonal gammopathy-related kidney diseases

BACKGROUND AND OBJECTIVES

Multiple myeloma is responsible for a wide variety of renal pathologies. Urinary protein and monoclonal spike cannot be used to diagnose cast nephropathy (CN). Because albuminuria is a hallmark of glomerular disease, this study evaluated the percentage of urinary albumin excretion (%UAE) as a tool to differentiate CN from Ig light chain amyloidosis (AL), light chain deposition disease (LCDD), and acute tubular necrosis (ATN).

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Patients were selected from the Renal Biopsy Database and the Dysproteinemia Database. Participants were excluded if laboratory data were missing within 1 week of the renal biopsy. The %UAE was obtained from urine protein electrophoresis.

RESULTS

From 1992 to 2011, 260 patients were biopsied (177 with AL, 28 with LCDD, 43 with CN, and 12 with ATN). The %UAE for CN patients was significantly lower (7%) than for ATN (25%), LCDD (55%), and AL (70%) patients (P<0.001). Significant differences were also found in serum creatinine, serum albumin, free light chain ratio, total urine protein, and urine monoclonal spike; only the %UAE remained independently associated with CN in a logistic regression model (P<0.001). The area under the curve for the receiver operator characteristic curve for %UAE was 0.99. At <25%, the %UAE had a sensitivity of 0.98, specificity of 0.94, positive predictive value of 0.75, and negative predictive value of 0.99.

CONCLUSIONS

This study showed that %UAE was significantly less in CN than the other three renal lesions and %UAE may thus be helpful in diagnosis of CN.

Optimizing treatment strategies in myeloma cast nephropathy: rationale for a randomized prospective trial

Renal failure is a frequent complication of multiple myeloma (MM) that strongly affects patient survival. Although a variety of renal diseases may be observed in MM, myeloma cast nephropathy (MCN), a tubulo-interstitial disorder related to precipitation of a monoclonal light chain (LC) within tubular distal lumens, is the main cause of severe and persistent renal failure. To date, the respective frequency and initial evolution of renal disorders associated with monoclonal LC in MM remain poorly defined. Treatment of MCN relies on urgent symptomatic measures and rapid introduction of chemotherapy to reduce the production of monoclonal LC. The introduction of novel chemotherapy regimens based on the association of bortezomib with dexamethasone is likely to have improved the prognosis of MM patients with renal failure. In addition, the combination of novel agents with efficient removal of circulating LC through high cut-off hemodialysis membrane may further increase renal response rate. However, the impact on patient and renal outcomes of these potential therapeutic advances has not been evaluated in prospective studies. The randomized trials EuLITE in the UK and Germany and MYRE in France should help to answer these issues. MYRE is a randomized controlled phase III trial (NCT01208818) that aims to better define the epidemiology and typology of inaugural renal failure in MM and to optimize therapy of MCN patients with and without dialysis-dependent renal failure.

The rationale and evidence base for the direct removal of serum-free light chains in the management of myeloma kidney

Myeloma kidney (cast nephropathy) causing severe acute kidney injury occurs in up to 10% of patients with multiple myeloma. The lesion is caused by exposure of the kidneys to high serum levels of free clonal immunoglobulin light chains (LCs) and is associated with very high morbidity and mortality. The current focus on the management of this complication is on early and aggressive treatment to rapidly reduce the serum levels of the immunoglobulin LC clone and protect the kidneys from continuing injury. This has promoted intense interest in the role of direct (extracorporeal) removal of free LCs from serum by plasma exchange or high cut-off (protein permeable) hemodialysis. However, it remains uncertain whether direct removal provides an additional measurable clinical benefit over the current standard of care; rapid institution of treatment with a dexamethasone- and bortezomib-based chemotherapy regime. In this article, we review the rationale for direct removal of free LCs and the current clinical evidence base for plasma exchange and high cut-off hemodialysis.

Current approach to diagnosis and management of acute renal failure in myeloma patients

Renal impairment is a serious complication of multiple myeloma. The primary cause of renal failure in myeloma is damage to the kidney by excessive amounts of light chain produced by the myeloma tumor, giving rise to cast nephropathy (myeloma kidney), although there are several other important precipitants. Significantly poor prognosis is observed in patients who do not recover their renal function; however, with the advent of more effective therapies and a greater understanding of the pathogenesis of the underlying process, it has become possible to reverse renal impairment in greater numbers of patients. Determining whether the renal impairment is due to cast nephropathy should be the first priority, and once the diagnosis is confirmed, appropriate treatment should be initiated without delay. Reduction of serum free light chain is the key to recovery of renal function in these patients. The role of chemotherapy and extracorporeal removal of light chain are discussed.

Amyloidosis

The term amyloid describes the deposition in the extracellular space of certain proteins in a highly characteristic, insoluble fibrillar form. Amyloidosis describes the various clinical syndromes that occur as a result of damage by amyloid deposits in tissues and organs throughout the body. The clinical significance of amyloid varies enormously, ranging from incidental asymptomatic deposits to localized disease through to rapidly fatal systemic forms that can affect multiple vital organs. Currently available therapy is focused on reducing the supply of the respective amyloid fibril precursor protein and supportive medical care, which together have greatly improved survival. Chemotherapy and anti-inflammatory treatment for the disorders that underlie AL and AA amyloidosis are guided by serial measurements of the respective circulating amyloid precursor proteins, i.e. serial serum free light chains in AL and serum amyloid A protein in AA type. Quality of life and prognosis of some forms of hereditary systemic amyloidosis can be improved by liver and other organ transplants. Various new therapies, ranging from silencing RNA, protein stabilizers to monoclonal antibodies, aimed at inhibiting fibril precursor supply, fibril formation or the persistence of amyloid deposits, are in development; some are already in clinical phase.

Systemic AA amyloidosis

Systemic AA amyloidosis is a rare complication of chronic inflammatory disorders. The amyloid fibrils are derived from serum amyloid A protein, an acute phase protein synthesized in the liver. Clinical presentation is most commonly due to the consequences of renal involvement, with proteinuria and progressive renal decline. Progression to end stage renal failure is common. Management is currently centred on reducing the supply of the precursor protein by treating the underlying inflammatory condition, whilst supporting the affected organs. Monitoring of the serum amyloid A protein is vital to assess whether there is adequate suppression of the underlying disease. The level of serum amyloid A protein is a powerful predictor of both patient survival and renal outcome. In patients with adequate suppression of the serum amyloid A protein amyloid deposits can be seen to regress and renal function can be stabilised and even improve.

Early reduction of serum-free light chains associates with renal recovery in myeloma kidney

Myeloma kidney is the major cause of severe irreversible renal failure in patients with multiple myeloma. This tubulointerstitial injury is a direct consequence of high concentrations of circulating monoclonal free light chains (FLCs) produced by a clonal expansion of plasma cells. Early reduction of serum FLCs associates with renal recovery, but the target threshold of reduction to facilitate renal recovery is unknown. To determine the relationship between the achieved FLC reduction and renal recovery, we identified 39 patients with biopsy-proven myeloma kidney, the majority of whom had severe renal failure at presentation (median estimated GFR 9 ml/min per 1.73 m²). In a multivariable analysis incorporating demographic, hematologic, and renal variables, only the achieved FLC reduction significantly predicted renal recovery (P = 0.003). The relationship between renal recovery and FLC reduction was linear with no absolute threshold for FLC reduction. A 60% reduction in FLCs by day 21 associated with recovery of renal function for 80% of the population. Patient survival strongly associated with renal recovery: the median survival was 42.7 months (range 0 to 80) among those who recovered function compared with 7.8 months (range 0 to 54) among those who did not (P < 0.02). Cox-regression analysis demonstrated that the first presentation of myeloma, the kappa isotype of FLC, and renal recovery were independent predictors of survival. In conclusion, recovery of renal function in myeloma kidney depends on early reduction of serum FLCs, and this recovery associates with a significant survival advantage.