The role of bone biopsy in patients with chronic renal failure

Bone Health ECHO Case Report: Fractures and Hypercalcemia in a Patient with Stage 5 Chronic Kidney Disease

Bone Health ECHO (Extension for Community Healthcare Outcomes) is a virtual community of practice with the aim of enhancing global capacity to deliver best practice skeletal healthcare. The prototype program, established at the University of New Mexico, has been meeting online weekly since 2015, focusing on presentation and discussion of patient cases. These discussions commonly cover issues that are relevant to a broad range of patients, thereby serving as a force multiplier to improve the care of many patients. This is a case report from Bone Health ECHO about a patient with stage 5 chronic kidney disease, hypercalcemia, and low bone density, and the discussion that followed.

Recommendations of the Spanish Society of Nephrology for the management of mineral and bone metabolism disorders in patients with chronic kidney disease: 2021 (SEN-MM)

As in 2011, when the Spanish Society of Nephrology (SEN) published the Spanish adaptation to the Kidney Disease: Improving Global Outcomes (KDIGO) universal Guideline on Chronic Kidney Disease-Mineral and Bone Disorder (CKD-MBD), this document contains an update and an adaptation of the 2017 KDIGO guidelines to our setting. In this field, as in many other areas of nephrology, it has been impossible to irrefutably answer many questions, which remain pending. However, there is no doubt that the close relationship between the CKD-MBD/cardiovascular disease/morbidity and mortality complex and new randomised clinical trials in some areas and the development of new drugs have yielded significant advances in this field and created the need for this update. We would therefore highlight the slight divergences that we propose in the ideal objectives for biochemical abnormalities in the CKD-MBD complex compared to the KDIGO suggestions (for example, in relation to parathyroid hormone or phosphate), the role of native vitamin D and analogues in the control of secondary hyperparathyroidism and the contribution of new phosphate binders and calcimimetics. Attention should also be drawn to the adoption of important new developments in the diagnosis of bone abnormalities in patients with kidney disease and to the need to be more proactive in treating them. In any event, the current speed at which innovations are taking place, while perhaps slower than we might like, globally drives the need for more frequent updates (for example, through Nefrología al día).

Management of fracture risk in CKD-traditional and novel approaches

The coexistence of osteoporosis and chronic kidney disease (CKD) is an evolving healthcare challenge in the face of increasingly aging populations. Globally, accelerating fracture incidence causes disability, impaired quality of life and increased mortality. Consequently, several novel diagnostic and therapeutic tools have been introduced for treatment and prevention of fragility fractures. Despite an especially high fracture risk in CKD, these patients are commonly excluded from interventional trials and clinical guidelines. While management of fracture risk in CKD has been discussed in recent opinion-based reviews and consensus papers in the nephrology literature, many patients with CKD stages 3-5D and osteoporosis are still underdiagnosed and untreated. The current review addresses this potential treatment nihilism by discussing established and novel approaches to diagnosis and prevention of fracture risk in patients with CKD stages 3-5D. Skeletal disorders are common in CKD. A wide variety of underlying pathophysiological processes have been identified, including premature aging, chronic wasting, and disturbances in vitamin D and mineral metabolism, which may impact bone fragility beyond established osteoporosis. We discuss current and emerging concepts of CKD-mineral and bone disorders (CKD-MBD) and integrate management of osteoporosis in CKD with current recommendations for management of CKD-MBD. While many diagnostic and therapeutic approaches to osteoporosis can be applied to patients with CKD, some limitations and caveats need to be considered. Consequently, clinical trials are needed that specifically study fracture prevention strategies in patients with CKD stages 3-5D.

Evaluating Patients for Secondary Causes of Osteoporosis

PURPOSE OF REVIEW

This review provides suggestions for the evaluation of patients with osteoporosis in order to assure that the diagnosis is correct, to identify potentially correctable conditions contributing to skeletal fragility and fracture risk, and to assist in individualizing management decisions.

RECENT FINDINGS

Some patients who appear to have osteoporosis have another skeletal disease, such as osteomalacia, that requires further evaluation and treatment that is different than for osteoporosis. Many patients with osteoporosis have contributing factors (e.g., vitamin D deficiency, high fall risk) that should be addressed before and after starting treatment to assure that treatment is effective and safe. Evaluation includes a focused medical history, skeletal-related physical examination, assessment of falls risk, appropriate laboratory tests, and rarely transiliac double-tetracycline labeled bone biopsy. Evaluation of patients with osteoporosis before starting treatment is essential for optimizing clinical outcomes.

Kidney Function Change and All-Cause Mortality in Denosumab Users with and without Chronic Kidney Disease

Denosumab is approved for osteoporosis treatment in subjects with and without chronic kidney disease (CKD). Confirmation is required for its safety, treatment adherence, renal function effect, and mortality in patients with CKD. A retrospective cohort study was conducted to compare new users of denosumab in terms of their two-year drug adherence in all participants (overall cohort) and CKD participants (CKD subcohort), which was defined as baseline estimated glomerular filtration rate (eGFR) less than 60 mL/min/1.73 m². The eGFR was calculated using the 2021 CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equation. We defined high adherence (HA) users as receiving three or four doses and low adherence (LA) users as receiving one or two doses. All-cause mortality was analyzed using Kaplan–Meier curves and Cox regression models. In total, there were 1142 subjects in the overall cohort and 500 subjects in the CKD subcohort. HA users had better renal function status at baseline than LD users in the overall cohort. A decline in renal function was only observed among LD users in the overall cohort. In the CKD subcohort, no baseline renal function difference or renal function decline was demonstrated. The all-cause mortality rate of HA users was lower than LA users in both the overall cohort and CKD. A randomized control trial is warranted to target this unique population to confirm our observations.

Bone Histomorphometry and 18F-Sodium Fluoride Positron Emission Tomography Imaging: Comparison Between only Bone Turnover-based and Unified TMV-based Classification of Renal Osteodystrophy

Bone biopsy is the gold standard for characterization of renal osteodystrophy (ROD). However, the classification of the subtypes of ROD based on histomorphometric parameters is not unambiguous and the range of normal values for turnover differ in different publications. ¹⁸F-Sodium Fluoride positron emission tomography (¹⁸F-NaF PET) is a dynamic imaging technique that measures turnover. ¹⁸F-NaF PET has previously been shown to correlate with histomorphometric parameters. In this cross-sectional study, 26 patients on dialysis underwent a ¹⁸F-NaF PET and a bone biopsy. Bone turnover-based classification was assessed using Malluche's historical reference values for normal bone turnover. In unified turnover-mineralization-volume (TMV)-based classification, the whole histopathological picture was evaluated and the range for normal turnover was set accordingly. Fluoride activity was measured in the lumbar spine (L1-L4) and at the anterior iliac crest. On the basis of turnover-based classification of ROD, 12% had high turnover and 61% had low turnover bone disease. On the basis of unified TMV-based classification of ROD, 42% had high turnover/hyperparathyroid bone disease and 23% had low turnover/adynamic bone disease. When using unified TMV-based classification of ROD, ¹⁸F-NaF PET had an AUC of 0.86 to discriminate hyperparathyroid bone disease from other types of ROD and an AUC of 0.87, for discriminating adynamic bone disease. There was a disproportion between turnover-based classification and unified TMV-based classification. More research is needed to establish normal range of bone turnover in patients with CKD and to establish the role of PET imaging in ROD.

Bone Biopsy for Histomorphometry in Chronic Kidney Disease (CKD): State-of-the-Art and New Perspectives

The use of bone biopsy for histomorphometric analysis is a quantitative histological examination aimed at obtaining quantitative information on bone remodeling, structure and microarchitecture. The labeling with tetracycline before the procedure also allows for a dynamic analysis of the osteoblastic activity and mineralization process. In the nephrological setting, bone biopsy is indicated to confirm the diagnosis of subclinical or focal osteomalacia and to characterize the different forms of renal osteodystrophy (ROD). Even if bone biopsy is the gold standard for the diagnosis and specific classification of ROD, the use of this approach is very limited. The main reasons for this are the lack of widespread expertise in performing or interpreting bone biopsy results and the cost, invasiveness and potential pain associated with the procedure. In this regard, the sedation, in addition to local anesthesia routinely applied in Italian protocol, significantly reduces pain and ameliorates the pain perception of patients. Concerning the lack of widespread expertise, in Italy a Hub/Spokes model is proposed to standardize the analyses, optimizing the approach to CKD patients and reducing the costs of the procedure. In addition, new tools offer the possibility to evaluate the osteogenic potential or the ability to form bone under normal and pathological conditions, analyzing mesenchymal stem cells and their ability to differentiate in the osteogenic lineage. In the same way, circulating microRNAs are suggested as a tool for exploring osteogenic potential. The combination of different diagnostic approaches and the optimization of the bioptic procedure represent a concrete solution to spread the use of bone biopsy and optimize CKD patient management.

Osteoporosis and Chronic Kidney Disease-Mineral and Bone Disorder (CKD-MBD): Back to Basics

Osteoporosis is defined as a skeletal disorder of compromised bone strength predisposing those affected to an elevated risk of fracture. However, based on bone histology, osteoporosis is only part of a spectrum of skeletal complications that includes osteomalacia and the various forms of renal osteodystrophy of chronic kidney disease-mineral and bone disorder (CKD-MBD). In addition, the label "kidney-induced osteoporosis" has been proposed, even though the changes caused by CKD do not qualify as osteoporosis by the histological diagnosis. It is clear, therefore, that such terminology may not be helpful diagnostically or in making treatment decisions. A new label, "CKD-MBD/osteoporosis" could be a more appropriate term because it brings osteoporosis under the official label of CKD-MBD. Neither laboratory nor noninvasive diagnostic investigations can discriminate osteoporosis from the several forms of renal osteodystrophy. Transiliac crest bone biopsy can make the diagnosis of osteoporosis by exclusion of other kidney-associated bone diseases, but its availability is limited. Recently, a classification of metabolic bone diseases based on bone turnover, from low to high, together with mineralization and bone volume, has been proposed. Therapeutically, no antifracture treatments have been approved by the US Food and Drug Administration for patients with kidney-associated bone disease. Agents that suppress parathyroid hormone (vitamin D analogues and calcimimetics) are used to treat hyperparathyroid bone disease. Antiresorptive and osteoanabolic agents approved for osteoporosis are being used off-label to treat CKD stages 3b-5 in high-risk patients. It has now been suggested that intermittent administration of parathyroid hormone as early as CKD stage 2 could be an effective management strategy. If confirmed in clinical trials, it could mitigate the retention of phosphorus and subsequently the rise in fibroblast growth factor 23 and may be beneficial for coexisting osteoporosis.

Denosumab Safety and Efficacy Among Participants in the FREEDOM Extension Study With Mild to Moderate Chronic Kidney Disease

CONTEXT

The effects of long-term exposure to denosumab in individuals with renal insufficiency are unknown.

OBJECTIVE

This post hoc analysis evaluates the long-term safety and efficacy of denosumab in individuals with mild-to-moderate chronic kidney disease (CKD) (stages 2 and 3) using data from the pivotal phase 3, double-blind, 3-year FREEDOM (NCT00089791) and open-label, 7-year extension (NCT00523341) studies.

PARTICIPANTS AND METHODS

Women age 60 to 90 years with a bone mineral density (BMD) T-score of less than -2.5 to greater than -4.0 at the total hip or lumbar spine were randomly assigned 1:1 to receive denosumab 60 mg subcutaneously every 6 months (long-term arm) or placebo (cross-over arm) in FREEDOM; eligible participants could enroll in the extension to receive denosumab 60 mg subcutaneously every 6 months. Change in estimated glomerular filtration rate (eGFR) from study baseline and annualized rates of fracture and adverse events (AEs) were the main outcome measures.

RESULTS

Most participants (1259/1969 [64%] long-term arm; 1173/1781 [66%] crossover arm) with baseline CKD stage 2 or 3 remained within the same CKD subgroup at study completion; less than 3% progressed to CKD stage 4. Participants in all eGFR subgroups showed similar, persistent BMD gains over time and a low incidence of fractures. The percentage of participants reporting serious AEs was similar among renal subgroups (normal, CKD stage 2, CKD stage 3a, CKD stage 3b) both for the long-term (54% vs 52% vs 57% vs 58%) and crossover (43% vs 42% vs 43% vs 68%) arms, except CKD stage 3b subgroup, crossover arm.

CONCLUSION

The safety and efficacy of denosumab did not differ among participants with mild to moderate CKD.

Correlation between 18F-Sodium Fluoride positron emission tomography and bone histomorphometry in dialysis patients

BACKGROUND

The diagnosis of renal osteodystrophy is challenging. Bone biopsy is the gold standard, but it is invasive and limited to one site of the skeleton. The ability of biomarkers to estimate the underlying bone pathology is limited. ¹⁸F-Sodium Fluoride positron emission tomography (¹⁸F-NaF PET) is a noninvasive quantitative imaging technique that allows assessment of regional bone turnover at clinically relevant sites. The hypothesis of this study was, that ¹⁸F-NaF PET correlates with bone histomorphometry in dialysis patients and could act as a noninvasive diagnostic tool in this patient group.

METHODS

This was a cross-sectional diagnostic test study. 26 dialysis patients with biochemical abnormalities indicating mineral and bone disorder were included. All the participants underwent a ¹⁸F-NaF PET scan and a bone biopsy. Fluoride activity in the PET scan was measured in the lumbar spine and at the anterior iliac crest. Dynamic and static histomorphometric parameters of the bone biopsy were assessed. As histomorphometric markers for bone turnover we used bone formation rate per bone surface (BFR/BS) and activation frequency per year (Ac.f).

RESULTS

There was a statistically significant correlation between fluoride activity in the ¹⁸F-NaF PET scan and histomorphometric parameters such as bone formation rate, activation frequency and osteoclast and osteoblast surfaces and mineralized surfaces. ¹⁸F-NaF PET's sensitivity to recognize low turnover in respect to non-low turnover was 76% and specificity 78%. Because of the small number of patients with high turnover, we were unable to demonstrate significant predictive value in this group.

CONCLUSIONS

A clear correlation between histomorphometric parameters and fluoride activity in the ¹⁸F-NaF PET scan was established. ¹⁸F-NaF PET may possibly be a noninvasive diagnostic tool in dialysis patients with low turnover bone disease, but further research is needed.

Assessment of Renal Osteodystrophy via Computational Analysis of Label-free Raman Detection of Multiple Biomarkers

Accurate clinical evaluation of renal osteodystrophy (ROD) is currently accomplished using invasive in vivo transiliac bone biopsy, followed by in vitro histomorphometry. In this study, we demonstrate that an alternative method for ROD assessment is through a fast, label-free Raman recording of multiple biomarkers combined with computational analysis for predicting the minimally required number of spectra for sample classification at defined accuracies. Four clinically relevant biomarkers: the mineral-to-matrix ratio, the carbonate-to-matrix ratio, phenylalanine, and calcium contents were experimentally determined and simultaneously considered as input to a linear discriminant analysis (LDA). Additionally, sample evaluation was performed with a linear support vector machine (LSVM) algorithm, with a 300 variable input. The computed probabilities based on a single spectrum were only marginally different (~80% from LDA and ~87% from LSVM), both providing an unacceptable classification power for a correct sample assignment. However, the Type I and Type II assignment errors confirm that a relatively small number of independent spectra (7 spectra for Type I and 5 spectra for Type II) is necessary for a p < 0.05 error probability. This low number of spectra supports the practicality of future in vivo Raman translation for a fast and accurate ROD detection in clinical settings.

Raman Spectroscopic and Microscopic Analysis for Monitoring Renal Osteodystrophy Signatures

Defining the pathogenesis of renal osteodystrophy (ROD) and its treatment efficacy are difficult, since many factors potentially affect bone quality. In this study, confocal Raman microscopy and parallel statistical analysis were used to identify differences in bone composition between healthy and ROD bone tissues through direct visualization of three main compositional parametric ratios, namely, calcium content, mineral-to-matrix, and carbonate-to-matrix. Besides the substantially lower values found in ROD specimens for these representative ratios, an obvious accumulation of phenylalanine is Raman spectroscopically observed for the first time in ROD samples and reported here. Thus, elevated phenylalanine could also be considered as an indicator of the disease. Since the image results are based on tens of thousands of spectra per sample, not only are the average ratios statistically significantly different for normal and ROD bone, but the method is clearly powerful in distinguishing between the two types of samples. Furthermore, the statistical outcomes demonstrate that only a relatively small number of spectra need to be recorded in order to classify the samples. This work thus opens the possibility of future development of in vivo Raman sensors for assessment of bone structure, remodeling, and mineralization, where different biomarkers are simultaneously detected with unprecedented accuracy.

Proceedings of the 2016 Santa Fe Bone Symposium: New Concepts in the Management of Osteoporosis and Metabolic Bone Diseases

The Santa Fe Bone Symposium is an annual meeting of healthcare professionals and clinical researchers that details the clinical relevance of advances in knowledge of skeletal diseases. The 17th Santa Fe Bone Symposium was held in Santa Fe, New Mexico, USA, on August 5-6, 2016. The program included plenary lectures, oral presentations by endocrinology fellows, meet-the-professor sessions, and panel discussions, all aimed to provide ample opportunity for interactive discussions among all participants. Symposium topics included recent developments in the translation of basic bone science to patient care, new clinical practice guidelines for postmenopausal osteoporosis, management of patients with disorders of phosphate metabolism, new and emerging treatments for rare bone diseases, strategies to enhance fracture healing, and an update on Bone Health Extension for Community Healthcare Outcomes, using a teleconferencing platform to elevate the level of knowledge of healthcare professionals in underserved communities to deliver best practice care for skeletal diseases. The highlights and important clinical messages of the 2016 Santa Fe Bone Symposium are provided herein by each of the faculty presenters.

Conventional hemodialysis is associated with greater bone loss than nocturnal hemodialysis: a retrospective observational study of a convenience cohort

Background

Compared with the general population, end-stage renal disease patients are at increased risk for bone loss and fractures. Nocturnal hemodialysis offers superior calcium-phosphate control and improved uremic clearance compared with conventional hemodialysis. Rates of bone loss by type of hemodialysis are unknown.

Objectives

This study aims to determine whether there are differences in bone loss between frequent nocturnal hemodialysis and conventional hemodialysis.

Design

This is a retrospective observational study.

Setting

Participants were selected from two teaching hospitals in downtown Toronto.

Participants

The study included 88 participants on dialysis for at least 6 months (52 patients on conventional hemodialysis and 36 patients converted from conventional hemodialysis to nocturnal hemodialysis). Patients on peritoneal dialysis and with previous renal transplants were excluded.

Measurements

We obtained demographic variables and biochemical data by a chart review. We examined changes in bone mineral density at the hip (femoral neck, total hip) and spine (L1 to L4) measured at baseline and about 1 year in the two groups.

Methods

We used Student’s t test for evaluation of between-group mean differences in demographic and biochemical parameters. We used linear regression models adjusted for baseline age, weight, dialysis vintage, markers of mineral metabolism (serum phosphate, serum calcium, and parathyroid hormone), and baseline bone mineral density at the femoral neck, total hip, and lumbar spine to determine the annualized percent change by hemodialysis type.

Results

Conventional hemodialysis subjects were older than nocturnal hemodialysis subjects (66 ± 9 vs 43 ± 10 years; p < 0.0001) with no significant differences in weight, dialysis vintage, serum phosphate, or parathyroid hormone between the two groups at baseline. In a period over 1 year, conventional hemodialysis compared to nocturnal hemodialysis subjects had significantly greater bone mineral density losses at all sites (1.6 % loss at the lumbar spine (95 % confidence interval (CI) 0.2–3.1), 1.3 % loss at the femoral neck (95 % CI 0.1–2.5), and 1.1 % loss at the total hip (95 % CI 0.1–2.6).

Limitations

Some limitations to this study are the lack of medication administration history, short duration (~1 year), and small sample sizes.

Conclusions

This is the first study comparing bone density between hemodialysis modalities. Our study demonstrates that bone loss is less in nocturnal hemodialysis compared to that in conventional hemodialysis which may result in less fractures. Larger observational studies are ultimately needed to confirm preliminary findings from our study.

Reversible Deterioration in Hypophosphatasia Caused by Renal Failure With Bisphosphonate Treatment

Hypophosphatasia is an inborn error of metabolism caused by mutations in the ALPL gene. It is characterized by low serum alkaline phosphatase (ALP) activity and defective mineralization of bone, but the phenotype varies greatly in severity depending on the degree of residual enzyme activity. We describe a man with compound heterozygous mutations in ALPL, but no previous bone disease, who suffered numerous disabling fractures after he developed progressive renal failure (for which he eventually needed dialysis treatment) and was prescribed alendronate treatment. A bone biopsy showed marked osteomalacia with low osteoblast numbers and greatly elevated pyrophosphate concentrations at mineralizing surfaces. In vitro testing showed that one mutation, T117H, produced an ALP protein with almost no enzyme activity; the second, G438S, produced a protein with normal activity, but its activity was inhibited by raising the media phosphate concentration, suggesting that phosphate retention (attributable to uremia) could have contributed to the phenotypic change, although a pathogenic effect of bisphosphonate treatment is also likely. Alendronate treatment was discontinued and, while a suitable kidney donor was sought, the patient was treated for 6 months with teriparatide, which significantly reduced the osteomalacia. Eighteen months after successful renal transplantation, the patient was free of symptoms and the scintigraphic bone lesions had resolved. A third bone biopsy showed marked hyperosteoidosis but with plentiful new bone formation and a normal bone formation rate. This case illustrates how pharmacological (bisphosphonate treatment) and physiologic (renal failure) changes in the "environment" can dramatically affect the phenotype of a genetic disorder.

Chronic kidney disease and the skeleton

Fractures across the stages of chronic kidney disease (CKD) could be due to osteoporosis, some form of renal osteodystrophy defined by specific quantitative histomorphometry or chronic kidney disease-mineral and bone disorder (CKD-MBD). CKD-MBD is a systemic disease that links disorders of mineral and bone metabolism due to CKD to either one or all of the following: abnormalities of calcium, phosphorus, parathyroid hormone or vitamin D metabolism; abnormalities in bone turnover, mineralization, volume, linear growth or strength; or vascular or other soft-tissue calcification. Osteoporosis, as defined by the National Institutes of Health, may coexist with renal osteodystrophy or CKD-MBD. Differentiation among these disorders is required to manage correctly the correct disorder to reduce the risk of fractures. While the World Health Organization (WHO) bone mineral density (BMD) criteria for osteoporosis can be used in patients with stages 1-3 CKD, the disorders of bone turnover become so aberrant by stages 4 and 5 CKD that neither the WHO criteria nor the occurrence of a fragility fracture can be used for the diagnosis of osteoporosis. The diagnosis of osteoporosis in stages 4 and 5 CKD is one of the exclusion-excluding either renal osteodystrophy or CKD-MBD as the cause of low BMD or fragility fractures. Differentiations among the disorders of renal osteodystrophy, CKD-MBD or osteoporosis are dependent on the measurement of specific biochemical markers, including serum parathyroid hormone (PTH) and/or quantitative bone histomorphometry. Management of fractures in stages 1-3 CKD does not differ in persons with or without CKD with osteoporosis assuming that there is no evidence for CKD-MBD, clinically suspected by elevated PTH, hyperphosphatemia or fibroblast growth factor 23 due to CKD. Treatment of fractures in persons with osteoporosis and stages 4 and 5 CKD is not evidence-based, with the exception of post-hoc analysis suggesting efficacy and safety of specific osteoporosis therapies (alendronate, risedronate and denosumab) in stage 4 CKD. This review also discusses how to diagnose and manage fragility fractures across the five stages of CKD.

Osteoporosis update: proceedings of the 2013 Santa Fe Bone Symposium

The 2013 Santa Fe Bone Symposium included plenary sessions on new developments in the fields of osteoporosis and metabolic bone disease, oral presentations of abstracts, and faculty panel discussions of common clinical conundrums: scenarios of perplexing circumstances where treatment decisions are not clearly defined by current medical evidence and clinical practice guidelines. Controversial issues in the care of osteoporosis were reviewed and discussed by faculty and participants. This is a review of the proceedings of the Santa Fe Bone Symposium, constituting in its entirety an update of advances in the understanding of selected bone disease topics of interest and the implications for managing patients in clinical practice. Topics included the associations of diabetes and obesity with skeletal fragility, the complexities and pitfalls in assessing the benefits and potential adverse effects of nutrients for treatment of osteoporosis, uses of dual-energy X-ray absorptiometry beyond measurement of bone mineral density, challenges in the care of osteoporosis in the very elderly, new findings on the role of osteocytes in regulating bone remodeling, and current concepts on the use of bone turnover markers in managing patients with chronic kidney disease who are at high risk for fracture.

Chronic kidney disease and osteoporosis: evaluation and management

Fractures across the stages of chronic kidney disease (CKD) could be due to osteoporosis, some form of renal osteodystrophy defined by specific quantitative histomorphometry or chronic kidney disease-mineral and bone disorder (CKD-MBD). CKD-MBD is a systemic disease that links disorders of mineral and bone metabolism due to CKD to either one or all of the following: abnormalities of calcium, phosphorus, parathyroid hormone or vitamin D metabolism; abnormalities in bone turnover, mineralization, volume, linear growth or strength; or vascular or other soft-tissue calcification. Osteoporosis, as defined by The National Institutes of Health, may coexist with renal osteodystrophy or CKD-MBD. Differentiation among these disorders is required to manage correctly the correct disorder to reduce the risk of fractures. While the World Health Organization (WHO) BMD criteria for osteoporosis can be used in patients with stages 1-3 CKD, the disorders of bone turnover become so aberrant by stages 4 and 5 CKD that neither the WHO criteria nor the occurrence of a fragility fracture can be used for the diagnosis of osteoporosis. The diagnosis of osteoporosis in stages 4 and 5 CKD is one of the exclusion-excluding either renal osteodystrophy or CKD-MBD as the cause of low BMD or fragility fractures. Differentiations among the disorders of renal osteodystrophy, CKD-MBD or osteoporosis are dependent on the measurement of specific biochemical markers, including serum parathyroid hormone (PTH) and/or quantitative bone histomorphometry. Management of fractures in stages 1-3 CKD does not differ in persons with or without CKD with osteoporosis assuming there is no evidence for CKD-MBD, clinically suspected by elevated PTH, hyperphosphatemia or fibroblast growth factor 23 due to CKD. Treatment of fractures in persons with osteoporosis and stages 4 and 5 CKD is not evidence based, with the exception of post hoc analysis suggesting efficacy and safety of specific osteoporosis therapies (alendronate, risedronate and denosumab) in stage 4 CKD. This review also discusses how to diagnose and manage fragility fractures across the five stages of CKD.

Bisphophonates in CKD patients with low bone mineral density

Patients with chronic kidney disease-mineral and bone disorder (CKD-MBD) have a high risk of bone fracture because of low bone mineral density and poor bone quality. Osteoporosis also features low bone mass, disarranged microarchitecture, and skeletal fragility, and differentiating between osteoporosis and CKD-MBD in low bone mineral density is a challenge and usually achieved by bone biopsy. Bisphosphonates can be safe and beneficial for patients with a glomerular filtration rate of 30 mL/min or higher, but prescribing bisphosphonates in advanced CKD requires caution because of the increased possibility of low bone turnover disorders such as osteomalacia, mixed uremic osteodystrophy, and adynamic bone, even aggravating hyperparathyroidism. Therefore, bone biopsy in advanced CKD is an important consideration before prescribing bisphosphonates. Treatment also may induce hypocalcemia in CKD patients with secondary hyperparathyroidism, but vitamin D supplementation may ameliorate this effect. Bisphosphonate treatment can improve both bone mineral density and vascular calcification, but the latter becomes more unlikely in patients with stage 3-4 CKD with vascular calcification but no decreased bone mineral density. Using bisphosphonates requires considerable caution in advanced CKD, and the lack of adequate clinical investigation necessitates more studies regarding its effects on these patients.

(18)F-fluoride positron emission tomography measurements of regional bone formation in hemodialysis patients with suspected adynamic bone disease

(18)F-fluoride positron emission tomography ((18)F-PET) allows the assessment of regional bone formation and could have a role in the diagnosis of adynamic bone disease (ABD) in patients with chronic kidney disease (CKD). The purpose of this study was to examine bone formation at multiple sites of the skeleton in hemodialysis patients (CKD5D) and assess the correlation with bone biopsy. Seven CKD5D patients with suspected ABD and 12 osteoporotic postmenopausal women underwent an (18)F-PET scan, and bone plasma clearance, K i, was measured at ten skeletal regions of interest (ROI). Fifteen subjects had a transiliac bone biopsy following double tetracycline labeling. Two CKD5D patients had ABD confirmed by biopsy. There was significant heterogeneity in K i between skeletal sites, ranging from 0.008 at the forearm to 0.028 mL/min/mL at the spine in the CKD5D group. There were no significant differences in K i between the two study groups or between the two subjects with ABD and the other CKD5D subjects at any skeletal ROI. Five biopsies from the CKD5D patients had single tetracycline labels only, including the two with ABD. Using an imputed value of 0.3 μm/day for mineral apposition rate (MAR) for biopsies with single labels, no significant correlations were observed between lumbar spine K i corrected for BMAD (K i/BMAD) and bone formation rate (BFR/BS), or MAR. When biopsies with single labels were excluded, a significant correlation was observed between K i/BMAD and MAR (r = 0.81, p = 0.008) but not BFR/BS. Further studies are required to establish the sensitivity of (18)F-PET as a diagnostic tool for identifying CKD patients with ABD.

Estimated GFR and fracture risk: a population-based study

BACKGROUND AND OBJECTIVES

Although patients with ESRD have a higher fracture risk than the general population, there is conflicting evidence regarding fracture incidence in those with CKD. This study sought to determine the association between estimated GFR (eGFR) and fracture rates.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This study identified 1,815,943 community-dwelling adults who had at least one outpatient serum creatinine measurement between 2002 and 2008. Patients with eGFR <15 ml/min per 1.73 m(2) and those who required dialysis were excluded. Incident fractures of the hip, wrist, and vertebrae were identified using diagnostic and procedure codes. Poisson regression was used to determine adjusted rates of each fracture type by eGFR, age, and sex.

RESULTS

The median age of the cohort was 47 years (interquartile range, 24), and 7.1% had eGFR <60 ml/min per 1.73 m(2). Over a median follow-up of 4.4 years, fracture rates increased with age at all sites. Within each age stratum, unadjusted rates increased with declining eGFR; however, adjusted rates were similar across eGFR categories. For example, among women aged 65-74 years, adjusted hip fracture rates were 3.41 per 1000 person-years (95% confidence interval, 2.30 to 4.53) and 4.58 per 1000 person-years (95% confidence interval, 0.02 to 9.14) in those with eGFR ≥90 and 15-29 ml/min per 1.73 m(2), respectively. Similar results were observed for wrist and vertebral fractures.

CONCLUSIONS

In contrast to earlier studies, patients with eGFR<60 ml/min per 1.73 m(2) do not appear to have increased rates of hip, wrist, and vertebral fractures independent of age and sex.

Kienböck's disease associated with radiocephalic fistula formation in a patient with end-stage renal disease

Kienböck's disease, which consists of osteonecrosis and collapse of the lunate bone, causes chronic pain and dysfunction of the wrist. Patients on hemodialysis are occasionally present with wrist pain, but Kienböck's disease is rarely reported in dialysis patients. This case study describes Kienböck's disease in a patient with end-stage renal disease on hemodialysis. A 39-year-old male with a 1-year history of hemodialysis presented with left wrist pain that increased progressively over 6 months. The patient had no history of trauma or any other risk factors known to be associated with Kienböck's disease. Physical examination of the wrist at the site of the arteriovenous fistula showed swelling and tenderness with decreased range of motion. Radiographic examination showed articular collapse and fracture of the body of lunate consistent with stage IIIb Kienböck's disease. An intercarpal arthrodesis with autogenous bone graft was performed.

Bisphosphonates in the treatment of osteoporosis

Bisphosphonates are widely used in the treatment of osteoporosis to reduce fracture risk. Because of their long retention time in bone and uncommon side effects, questions have been raised about the optimal duration of therapy. Potential side effects appear to be rare and may not be causally related. Although there is no strong science to guide "drug holidays," there appears to be some lingering antifracture benefit when treatment is stopped, so some time off treatment should be offered to most patients on long-term bisphosphonate therapy. For most patients with osteoporosis, the benefits of treatment outweigh the risks.

The consequences of chronic kidney disease on bone metabolism and growth in children

Growth retardation, decreased final height and renal osteodystrophy (ROD) are common complications of childhood chronic kidney disease (CKD), resulting from a combination of abnormalities in the growth hormone (GH) axis, vitamin D deficiency, hyperparathyroidism, hypogonadism, inadequate nutrition, cachexia and drug toxicity. The impact of CKD-associated bone and mineral disorders (CKD-MBD) may be immediate (serum phosphate/calcium disequilibrium) or delayed (poor growth, ROD, fractures, vascular calcifications, increased morbidity and mortality). In 2012, the clinical management of CKD-MBD in children needs to focus on three main objectives: (i) to provide an optimal growth in order to maximize the final height with an early management with recombinant GH therapy when required, (ii) to equilibrate calcium/phosphate metabolism so as to obtain acceptable bone quality and cardiovascular status and (iii) to correct all metabolic and clinical abnormalities that can worsen bone disease, growth and cardiovascular disease, i.e. metabolic acidosis, anaemia, malnutrition and 25(OH)vitamin D deficiency. The aim of this review is to provide an overview of the mineral, bone and vascular abnormalities associated with CKD in children in terms of pathophysiology, diagnosis and clinical management.

Massive, painful tumoral calcinosis in a long-term hemodialysis patient

In chronic dialysis patients, ectopic, extraosseous calcifications can cause significant morbidity. Uremic tumoral calcinosis is an uncommon and severe complication of dialysis therapy. It is defined as deposition of dense nodular calcium-containing masses surrounding the large joints of the body, generally associated with the presence of high serum calcium-and-phosphorus product. We describe a 69-year-old woman submitted to long-term chronic hemodialysis that developed painful, bilateral hip tumors. Radiographic investigation showed extensive periarticular calcifications, and a bone biopsy was suggestive of adynamic bone disease and contained substantial amounts of aluminum. The lesions were surgically excised, and the histological analysis demonstrated amorphous, calcified material associated with densely collagenized connective tissue.

[Mineral and bone disorders associated with chronic kidney disease]

Chronic renal failure (CRF) is frequent in patients with osteoporosis and the rheumatologist should be familiarized with basic diagnostic and treatment guidelines for bone mineral disease associated to this process. In patients with osteoporosis and stage I and II CRF, diagnosis and treatment does not vary from that in patients with normal RF. In stage III CRF, the focus will depend on the result of testing. In advanced stage CRF the approach should be coordinated with a nephrologist. In these cases it is possible to use antiresorptive agents although in well-selected and studied patients. The present review analyzes recent advances in this field with a focus on daily clinical practice.

The kidney and bisphosphonates

Bisphosphonates are eliminated from the human body by the kidney. Renal clearance is both by glomerular filtration and proximal tubular secretion. Bisphosphonates given rapidly in high doses in animal models have induced a variety of adverse renal effects, from glomerular sclerosis to acute tubular necrosis. Nevertheless in the doses that are registered for the management of postmenopausal osteoporosis (PMO), oral bisphosphonates have never been shown to adversely affect the kidney, even (in post-hoc analysis of clinical trial data) down to estimated glomerular filtration rates of 15 ml/min. In addition fracture risk reduction has also been observed in these populations with stage 4 chronic kidney disease (CKD) with age-related reductions in glomerular filtration rate (GFR). Intravenous zoledronic acid is safe when the infusion rate is no faster than 15 min though there have been short-term (days 9-11 post-infusion) increases in serum creatinine concentrations in a small sub-set of patients from the postmenopausal registration trials. For these reasons intravenous zoledronic acid should be avoided in patients with GFR levels <35 ml/min; and the patients should be well hydrated and have avoided the concomitant use of any agent that may impair renal function. Intravenous ibandronate has not to date been reported to induce acute changes in serum creatinine concentrations in the PMO clinical trial data, but the lack of head-to-head comparative data between ibandronate and zoledronic acid precludes knowing if one intravenous bisphosphonate is safer than the other. In patients with GFR levels <30-35 ml/min, the correct diagnosis of osteoporosis becomes more complex since other forms of renal bone disease, which require different management strategies than osteoporosis, need to be excluded before the assumption can be made that fractures and/or low bone mass are due to osteoporosis. In addition, in patients who may have pre-existing adynamic renal bone disease, there is a lack of evidence of any beneficial effect or harm by reducing bone turnover by any pharmacological agent, including bisphosphonates on bone strength or vascular calcification. Bisphosphonates are safe and effective for the management of osteoporosis when used in the right dose and in the right patient population for the right duration.

Osteoporosis update from the 2010 santa fe bone symposium

The 11th Santa Fe Bone Symposium was held in Santa Fe, NM, USA, on August 6-7, 2010. This annual event addresses clinically relevant advances in the fields of osteoporosis and metabolic bone disease. The venue includes plenary presentations by internationally recognized experts, oral presentations of abstracts, and interactive panel discussions of challenging cases and controversial issues. Attendees are active participants throughout the symposium program. Topics for the 2010 symposium included potential applications of novel technologies for the assessment of skeletal health for research and clinical practice; new and emerging treatments for osteoporosis; appropriate use of pharmacological agents to prevent osteoporosis; controversies with bisphosphonate therapy; practical applications of the World Health Organization fracture risk assessment tool (FRAX; World Health Organization Collaborating Centre for Metabolic Bone Diseases, University of Sheffield, UK); insights into the use of osteoanabolic agents to enhance fracture healing; and challenges in laboratory testing in the assessment of factors contributing to skeletal fragility. Concurrent sessions focused on critical thinking for technologists in the acquisition and analysis of data with dual-energy X-ray absorptiometry. The key messages from each presentation, including the best available medical evidence and potential current and future clinical applications, are provided here.

Kienböck's disease: unusual cause of acute onset wrist pain in a dialysis patient

Kienböck's disease is a rare disorder that presents with wrist pain and limitation of motion and is caused by avascular necrosis of the lunate bone. Dialysis patients occasionally present with wrist pain. However, Kienböck's disease is rarely reported in dialysis patients. We report a case of 52-year-old woman with a 28-year history of hemodialysis who presented with acute wrist pain. T1-weighted magnetic resonance imaging showed diffuse low intensity of the lunate bone, consistent with the diagnosis of Kienböck's disease. Because this disease can lead to chronic debilitating wrist pain, prompt diagnosis, accurate staging, and provision of appropriate treatment is mandatory.

Risk factors leading to reduced bone mineral density in hemodialysis patients with metabolic syndrome

Although metabolic syndrome (MS) is associated with low bone mineral density (BMD) in the general population, it is unknown whether similar associations exist in patients with chronic kidney disease. We investigated risk factors that can lead to low BMD values in hemodialysis patients with MS according to the diagnostic criteria set by International Diabetes Federation (IDF) in this study. A total of 64 patients with MS undergoing hemodialysis and 60 hemodialysis patients who were matched in terms of age, gender, and hemodialysis duration without MS were enrolled in the study. BMD was measured at lumbar vertebra (LV) and femur neck (FN) by performing dual-energy X-ray absorptiometry (DEXA). LV and/or FN-BMD results revealed that, of the hemodialysis patients with MS, 45% had osteoporosis and 48% had osteopenia. On the other hand, of the hemodialysis patients without MS, 42% had osteoporosis and 52% had osteopenia. Low BMD values were observed to be correlated negatively with age, hemodialysis period, and parathormone (PTH) both in the group with MS and in the group without MS. Height, weight, BMI, calcium, phosphorus, alkaline phosphatase, heparin, and vitamin D therapy and urea reduction ratio were not established to be correlated with BMD.

Bone histomorphometry: a concise review for endocrinologists and clinicians

Bone histomorphometry is a quantitative histological examination of an undecalcified bone biopsy performed to obtain quantitative information on bone remodeling and structure. Labeling agents taken before the procedure deposit at sites of bone formation allowing a dynamic analysis. Biopsy is indicated to make the diagnosis of subclinical osteomalacia, to characterize the different forms of renal osteodystrophy and to elucidate cases of unexplained skeletal fragility. Bone histomorphometric parameters are divided into structural and remodeling subgroups, with the latter being subdivided into static and dynamic categories. Metabolic bone disorders such as osteomalacia, hyperparathyroidism, hypothyroidism, osteoporosis and renal osteodystrophy display different histomorphometric profiles. Antiresorptive and anabolic drugs used for the treatment of osteoporosis also induce characteristic changes in the bone biopsy. Bone histomorphometry is an important research tool in the field of bone metabolism and provides information that is not available by any other investigative approach.

2009 Santa Fe Bone symposium

Osteoporosis is a common skeletal disease with serious clinical consequences because of fractures. Despite the availability of clinical tools to diagnose osteoporosis and assess fracture risk, and drugs proven to reduce fracture risk, it remains a disease that is underdiagnosed and undertreated. When treatment is started, it is commonly not taken correctly or long enough to be effective. Recent advances in understanding of the regulators and mediators of bone remodeling have led to new therapeutic targets and the development of drugs that may offer advantages over current agents in reducing the burden of osteoporotic fractures. Many genetic factors that play a role in the pathogenesis of osteoporosis and metabolic bone disease have now been identified. At the 2009 Santa Fe Bone Symposium, held in Santa Fe, New Mexico, USA, the links between advances in genetics, basic bone science, recent clinical trials, and new and emerging therapeutic agents were presented and explored. Socioeconomic challenges and opportunities in the care of osteoporosis were discussed. This is a collection of medical essays based on key presentations at the 2009 Santa Fe Bone Symposium.

Diagnosis and treatment of osteoporosis in chronic renal disease

Osteoporosis is the most prevalent metabolic bone disease leading to low-trauma (fragility) fractures worldwide. There is no reason why osteoporosis, as defined by different criteria, cannot accompany the derangements in bone metabolism that characterize chronic kidney disease (CKD). In fact, osteoporosis could and should be included in the broad characterization of CKD-mineral and bone disorder (CKD-MBD), as recently proposed by the Kidney Disease: Improving Global Outcomes working group. The pathophysiology leading to osteoporosis or CKD-MBD shares many common yet distinctly different pathways. Both pathways may lead to impairment of bone strength and low-trauma fractures. The challenge for clinical practice is how to discriminate between osteoporosis and CKD-MBD in fracturing patients. There is agreement that in the absence of aberrant biochemical tests suggesting CKD-MBD in stages 1 through 3 CKD, osteoporosis can be diagnosed using the World Health Organization criteria or development of low-trauma fractures. The distinction between osteoporosis and CKD-MBD becomes more difficult in stages 4 and 5 through 5D CKD. In fracturing patients with these levels of severe CKD, careful biochemical assessment of bone turnover markers and, in selected cases, bone biopsy is needed to eliminate CKD-MBD and to diagnose osteoporosis by exclusion. In stages 1 through 3 CKD, the current registered osteoporosis pharmacologic therapies can be used to treat osteoporosis. In stage 4, 5, and 5D these agents can be considered off-label, but only after very careful considerations and only in fracturing patients without CKD-MBD. We need better noninvasive means of discriminating among all these metabolic bone diseases and prospective data to guide us to the use of agents that alter bone remodeling in high-risk patients with more severe CKD.

Anti-resorptives in the management of osteoporosis

Bone-active agents that decrease bone turnover (the anti-resorptive agents) have been, to date, the most thoroughly studied pharmacological agents for the management of osteoporosis in a variety of populations - postmenopausal, male, and glucocorticoid-induced osteoporosis - and have received both Food and Drug Administration (FDA) and Committee for Medicinal Products for Human Use (CHMP) as well as other worldwide registrations for the management of these conditions. While the mechanisms of action of 'anti-resorptives' as a class differ, their effect on increasing bone strength and reducing the risk of fragility fractures share common pathways: an increase in bone mineral content, and a reduction in bone turnover. Within the category of anti-resorptives: estrogen, selective estrogen receptor modulators, tibolone, calcitonin, bisphosphonates and denosumab all reduce vertebral fractures risk, but differ in their ability to reduce the risk of non-vertebral fractures in randomized clinical trials. This chapter will discuss the data on these effects for each class of anti-resorptive agent.