Low bone mass in idiopathic renal stone formers: magnitude and significance

Beyond the kidney: extra-renal manifestations of monogenic nephrolithiasis and their significance

BACKGROUND

The objective of this study was to explore the frequency of occurrence of extra-renal manifestations associated with monogenic nephrolithiasis.

METHODS

A literature review was conducted to identify genes that are monogenic causes of nephrolithiasis. The Online Mendelian Inheritance in Man (OMIM) database was used to identify associated diseases and their properties. Disease phenotypes were ascertained using OMIM clinical synopses and sorted into 24 different phenotype categories as classified in OMIM. Disease phenotypes caused by the same gene were merged into a phenotypic profile of a gene (PPG) such that one PPG encompasses all related disease phenotypes for a specific gene. The total number of PPGs involving each phenotype category was measured, and the median phenotype category was determined. Phenotype categories were classified as overrepresented or underrepresented if the number of PPGs involving them was higher or lower than the median, respectively. Chi-square test was conducted to determine whether the number of PPGs affecting a given category significantly deviated from the median.

RESULTS

Fifty-five genes were identified as monogenic causes of nephrolithiasis. A total of six significantly overrepresented and three significantly underrepresented phenotype categories were identified (p < 0.05). Four phenotypic categories (growth, neurological, skeletal, and abdomen/gastrointestinal) are significantly overrepresented after Bonferroni correction for multiple comparisons (p < 0.002). Among all phenotypes, impaired growth is the most common manifestation.

CONCLUSION

Recognizing the extra-renal manifestations associated with monogenic causes of kidney stones is critical for earlier diagnosis and optimal care in patients.

Prevalence of osteoporosis in patients with nephrolithiasis and vice versa: a cumulative analysis

Purpose

Nephrolithiasis is thought to be a risk factor for osteoporosis, but data assessing if osteoporosis predisposes to the risk of nephrolithiasis are lacking. The present study aims to investigate whether patients with nephrolithiasis have a prominently higher prevalence of osteoporosis than the controls and vice versa via a cumulative analysis.

Methods

Four databases were used to detect the eligible studies. We calculated the relative risk (RR) with a 95% confidence interval (CI) to assess the combined effect. The methodologies for conducting this study followed the PRISMA guidelines and were registered in the PROSPERO (ID: CRD42023395875).

Results

Nine case-control or cohort studies with a total of 454,464 participants were finally included. Combined results indicated that there was a significantly higher prevalence of osteoporosis in patients with nephrolithiasis as compared to the general population without nephrolithiasis (overall RR from six studies= 1.204, 95%CI: 1.133 to 1.28, P< 0.001; heterogeneity: I2 = 34.8%, P= 0.162). Conversely, osteoporosis was significantly correlated to an increased risk of nephrolithiasis as compared to the controls without osteoporosis (overall RR from four studies= 1.505, 95%CI: 1.309 to 1.731, P< 0.001; I2 = 89.8%, P< 0.001). Sensitivity analysis on the two categories validated the above findings. No significant publication bias was identified in this study.

Conclusions

The present study highlighted a significantly high prevalence of osteoporosis in patients with nephrolithiasis and vice versa. This reciprocal association reminded the clinicians to conduct a regular follow-up assessment when managing patients with nephrolithiasis or osteoporosis, especially for the elderly.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/#searchadvanced, identifier CRD42023395875.

Vitamin D and Calcium Supplementation and Urolithiasis: A Controversial and Multifaceted Relationship

Patients with urolithiasis, and particularly those with hypercalciuria, frequently have a marked reduction of bone mineral content up to the levels of osteoporosis, with a significant increase in bone fracture risk. For these reasons, the indication to prescribe vitamin D and/or calcium supplementations is very frequent in such patients. On the other hand, both calcium supplementation, and even more vitamin D therapy, can worsen the risk of developing urolithiasis by increasing calcium, phosphate, and oxalate urinary excretion. Despite the clinical and practical relevance of this issue, the evidence on this topic is scarce and contradictory. Therefore, some concerns exist about how and whether to prescribe such supplements to a patient with a history of kidney stones. In this narrative review, we resume some pivotal pathophysiological concepts strictly related to the dealt topic, and we draw some considerations and personal opinions on the pros and cons of such prescriptions. Finally, we share with the reader our pragmatic algorithm for handling the urolithiasis risk in patients who have strong indications to be prescribed vitamin D and calcium supplementations.

Vascular Calcification Is Associated with Fetuin-A and Cortical Bone Porosity in Stone Formers

Background: Nephrolithiasis has been associated with bone loss and vascular calcification (VC), reflecting abnormal extraosseous calcium deposition. Fetuin-A (Fet-A) acts as a potent inhibitor of ectopic mineralization. The aim of the present study was to evaluate the prevalence of VC in stone formers (SF) and non-stone formers (NSF) and to investigate potential determinants of VC among SF, including circulating levels of Fet-A and bone microarchitecture parameters. Methods: Abdominal aortic calcification (AAC) was assessed using available computed tomography in SF and in age-, sex-, and BMI-matched NSF (potential living kidney donors). Serum Fet-A was measured in stored blood samples from SF. Bone microarchitecture parameters were obtained as a post hoc analysis of a cross-sectional cohort from young SF evaluated by high-resolution peripheral quantitative computed tomography (HR-pQCT). Results: A total of 62 SF (38.0 [28.0−45.3] years old) and 80 NSF (40.0 [37.0−45.8] years old) were included. There was no significant difference in AAC scores between SF and NSF. However, when dividing SF according to mean AAC score, below <5.8% (n = 33) or above ≥5.8% (n = 29), SF with higher AAC presented significantly higher BMI and tibial cortical porosity (Ct.Po) and significantly lower serum HDL, klotho, Fet-A, and eGFR. Urinary calcium did not differ between groups, but fractional excretion of phosphate was higher in the former. Upon multivariate regression, BMI, serum Fet-A, and tibial Ct.Po remained independently associated with AAC. Conclusions: This study suggests an association between reduced circulating Fet-A levels and increased bone Ct.Po with VC in SF.

Predictors of Bone Mineral Density in Kidney Stone Formers

Introduction

Nephrolithiasis is associated with an increased fracture risk, but predictors of bone mineral density (BMD) in stone formers (SFs) remain poorly defined.

Methods

We conducted a retrospective analysis in the Bern Kidney Stone Registry (BKSR), an observational cohort of kidney SFs. Inclusion criteria were age ≥18 years and ≥1 past stone episode. Participants with non–calcium (Ca)-containing kidney stones, a history of primary hyperparathyroidism or antiresorptive or anabolic bone treatment were excluded. Multivariable linear regression analyses were used to assess the association of blood and 24-hours urine parameters and stone composition with BMD at the lumbar spine and femoral neck.

Results

In the analysis, 504 participants were included, mean age was 46 years, and 76% were male. In multivariable analyses, fasting (β: −0.031; P = 0.042), postload (β: −0.059; P = 0.0028) and Δ postload − fasting (β: −0.053; P = 0.0029) urine Ca-to-creatinine ratios after 1 week of a sodium- and Ca- restricted diet and Ca oxalate dihydrate stone content (β: −0.042; P = 0.011) were negatively associated with z scores at the lumbar spine. At the femoral neck, alkaline phosphatase (β: −0.035; P = 0.0034) and parathyroid hormone (PTH) (β: −0.035; P = 0.0026) were negatively associated with z scores, whereas 24-hours urine Ca (β: 0.033; P = 0.0085), magnesium (β: 0.043; P = 3.5 × 10⁻⁴), and potassium (β: 0.032; P = 0.012) correlated positively with z scores at the femoral neck.

Conclusion

Our study reveals distinct predictors of BMD in SFs. Commonly available clinical parameters, such as kidney stone composition results, can be used to identify SFs at risk for low BMD.

Osteoporosis, Fractures, and Bone Mineral Density Screening in Veterans With Kidney Stone Disease

Whether a link exists between kidney stone disease and osteoporosis or fractures remains an open question. In this retrospective cohort study, we sought to determine the prevalence of osteoporosis and fractures and rate of bone mineral density screening by dual-energy X-ray absorptiometry (DXA) in patients with kidney stone disease. We examined nationwide data from the Veterans Health Administration and identified 531,431 patients with kidney stone disease between 2007 and 2015. Nearly 1 in 4 patients (23.6%, 95% confidence interval [CI] 23.5-23.7) with kidney stone disease had a prevalent diagnosis of osteoporosis or fracture. In patients with no prior history of osteoporosis or bone mineral density assessment before a kidney stone diagnosis, 9.1% were screened with DXA after their kidney stone diagnosis, of whom 20% were subsequently diagnosed with osteoporosis. Our findings provide support for wider use of bone mineral density screening in patients with kidney stone disease, including middle-aged and older men, a group less well recognized as at risk for osteoporosis or fractures. © 2021 American Society for Bone and Mineral Research (ASBMR).

Bisphosphonates and management of kidney stones and bone disease

PURPOSE OF REVIEW

Kidney stones are strongly associated with low bone density and bone fracture. Clinical management focuses on prevention of kidney stones and bone fracture. We reviewed literature of kidney stones and bone disease with a special focus on updates in therapeutic strategies. We will review the literature regarding dietary management, supplements, and medications and emphasize the recent studies on bisphosphonates and kidney stone management.

RECENT FINDINGS

Bisphosphonate medications are commonly used in management of low bone density. Previous studies showed that they reduce urinary calcium. A recent large prospective study found that bisphosphonates may reduce the risk of kidney stones in individuals who have low bone density. In addition to lowering urinary calcium, a recent study found that bisphosphonates may act as an inhibitor in the urinary space.

SUMMARY

There are multiple dietary and pharmacologic strategies that can be considered for kidney stones and bone disease, such as low salt and normal calcium diet, as well as thiazides, alkali, and bisphosphonate medications. Bisphosphonates may have an important role in reducing bone resorption and reducing overall risk of kidney stone and bone disease.

Practice patterns of kidney stone management across European and non-European centers: an in-depth investigation from the European Renal Stone Network (ERSN)

Rationale and objective

Kidney stones are a common condition in the general population, however, high-quality evidence for its management is scarce. We propose the creation of an international network with the aim of sharing practice patterns and patient data towards an improvement of our knowledge of the disease.

Study design

Cross-sectional survey.

Setting and participants

An online survey was circulated through several scientific societies. Items were grouped into six domains. Each center’s overall score (OS) was also calculated.

Analytical approach

Chi square and Mann–Whitney tests were performed for differences across centers.

Results

The countries that contributed most were Italy (8.6%), Turkey (6.6%), France and Spain (6.1%). Some type of nutritional work-up was implemented in 62% of centers. A DEXA scan was performed by 46% of centers, whereas some kind of acidification test was performed by 25% of centers. Most centers (80%) implemented blood investigations at least at baseline. With regard to 24-h urine exams, 7 out of 16 were performed by at least 50% of centers. Information on stone composition was collected by 58% of centers. The OS was significantly higher among higher-volume centers compared with lower-volume centers (p = 0.002). Significant differences between EU and non-EU centers were found.

Limitations

Cross-sectional design; no validation on information.

Conclusions

Our survey highlights the potential for the creation of a network of centers that could share information in a common database for observational research and for enrollment of patients in interventional trials.

Electronic supplementary material

The online version of this article (10.1007/s40620-020-00854-6) contains supplementary material, which is available to authorized users.

Metabolic effects of cholecalciferol supplementation in patients with calcium nephrolithiasis and vitamin D deficiency

INTRODUCTION

In this paper, we investigated whether cholecalciferol supplementation may increase the risk of stone recurrence in patients with calcium nephrolithiasis and Vitamin D deficiency.

METHODS

Thirty-three stone formers (56 ± 17 years old, 12 males) with 25(OH)D < 20 ng/mL were considered. Calcium excretion and urine supersaturation with calcium oxalate (ßCaOx) and brushite (ßbsh) were evaluated, both before and after cholecalciferol supplementation. Values of ß > 1 mean supersaturation. Cholecalciferol was prescribed as oral bolus of 100,000-200,000 IU, followed by weekly (5000-10,000 IU) or monthly (25,000-50,000 IU) doses. Calcium intake varied between 800 and 1000 mg/day. In urine, total nitrogen (TNE) was taken as an index of protein intake, sodium as a marker of dietary intake, and net acid excretion (NAE) as an index of acid-base balance.

RESULTS

TNE, sodium, and NAE did not change during the study (p = ns). Compared to baseline values, after cholecalciferol, both serum calcium and phosphate did not vary (p = ns); 25(OH)D increased from 11.8 ± 5.5 to 40.2 ± 12.2 ng/mL (p < 0.01); 1.25(OH)₂D increased from 41.6 ± 17.6 to 54 ± 16 pg/mL (p < 0.01); PTH decreased from 75 ± 27.2 to 56.7 ± 21.1 pg/mL (p < 0.01); urinary calcium increased from 2.7 ± 1.5 to 3.6 ± 1.6 mg/Kg b.w. (p < 0.01); ßbsh increased from 0.9 ± 0.7 to 1.3 ± 1.3 (p = 0.02); whereas ßCaOx varied but not significantly. Before cholecalciferol supplementation, 6/33 patients were hypercalciuric (i.e., urine Ca ≥ 4 mg/Kg b.w.) and increased to 13/33 after cholecalciferol supplementation (pX² = 0.03).

CONCLUSIONS

Cholecalciferol supplementation may increase calcium excretion, or reveal an underlying condition of absorptive hypercalciuria. This may increase both urine supersaturation with calcium salts and stone-forming risk.

Skeletal manifestations of renal disease in childhood

PURPOSE OF REVIEW

This review summarizes recent findings on musculoskeletal health in three chronic renal conditions of childhood: chronic kidney disease stages 2-5D, nephrotic syndrome, and urolithiasis. Findings with important clinical implications warranting further investigation are highlighted.

RECENT FINDINGS

Recent cohort studies have demonstrated a high burden of fracture and progressive deficits of cortical bone in children with chronic kidney disease. Lower cortical density is associated with incident fracture and may be an important therapeutic target. Parathyroid hormone and calcium are independent correlates of cortical density, and modifiable factors for fracture include parathyroid hormone and phosphate binder use. Children with nephrotic syndrome, even with normal renal function, have evidence of abnormal bone metabolism and structure, and vitamin D deficiency may be an important modifiable risk factor in this population. Urolithiasis has been associated with reduced bone mineral density and is increasingly common in children and adolescents. Population-based data found a significantly increased risk of fracture in adolescent males and young women.

SUMMARY

Recent findings substantiate concern regarding the particular vulnerability of the growing skeleton to chronic renal disease. Studies are needed to determine how to optimize assessment and management of bone health in children with these conditions, particularly in terms of calcium and vitamin D requirements, with the goal of improving childhood bone accrual for lifelong fracture prevention.

Low Bone Density and Bisphosphonate Use and the Risk of Kidney Stones

BACKGROUND AND OBJECTIVES

Previous studies have demonstrated lower bone density in patients with kidney stones, but no longitudinal studies have evaluated kidney stone risk in individuals with low bone density. Small studies with short follow-up reported reduced 24-hour urine calcium excretion with bisphosphonate use. We examined history of low bone density and bisphosphonate use and the risk of incident kidney stone as well as the association with 24-hour calcium excretion.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We conducted a prospective analysis of 96,092 women in the Nurses' Health Study II. We used Cox proportional hazards models to adjust for age, body mass index, thiazide use, fluid intake, supplemental calcium use, and dietary factors. We also conducted a cross-sectional analysis of 2294 participants using multivariable linear regression to compare 24-hour urinary calcium excretion between participants with and without a history of low bone density, and among 458 participants with low bone density, with and without bisphosphonate use.

RESULTS

We identified 2564 incident stones during 1,179,860 person-years of follow-up. The multivariable adjusted relative risk for an incident kidney stone for participants with history of low bone density compared with participants without was 1.39 (95% confidence interval [95% CI], 1.20 to 1.62). Among participants with low bone density, the multivariable adjusted relative risk for an incident kidney stone for bisphosphonate users was 0.68 (95% CI, 0.48 to 0.98). In the cross-sectional analysis of 24-hour urine calcium excretion, the multivariable adjusted mean difference in 24-hour calcium was 10 mg/d (95% CI, 1 to 19) higher for participants with history of low bone density. However, among participants with history of low bone density, there was no association between bisphosphonate use and 24-hour calcium with multivariable adjusted mean difference in 24-hour calcium of -2 mg/d (95% CI, -25 to 20).

CONCLUSIONS

Low bone density is an independent risk factor for incident kidney stone and is associated with higher 24-hour urine calcium excretion. Among participants with low bone density, bisphosphonate use was associated with lower risk of incident kidney stone but was not independently associated with 24-hour urine calcium excretion.

Dietary Zinc and Incident Calcium Kidney Stones in Adolescence

PURPOSE

We determined the association between dietary zinc intake and incident calcium kidney stones in adolescents. We also examined the relationship between dietary zinc intake and urinary zinc excretion between cases and controls.

MATERIALS AND METHODS

We conducted a nested case-control study within a large pediatric health care system. Three 24-hour dietary recalls and spot urine chemistry analyses were obtained for 30 participants 12 to 18 years old with a first idiopathic calcium based kidney stone and 30 healthy controls matched for age, sex, race and month of enrollment. Conditional logistic regression models were used to estimate the association between daily zinc intake and incident calcium kidney stones, adjusting for dietary phytate, protein, calcium, sodium and oxalate. Multivariable linear regression was used to estimate the association between dietary and urine zinc, adjusting for urine creatinine and dietary phytate and calcium.

RESULTS

Cases had lower daily zinc intake (8.1 mg) than controls (10 mg, p = 0.029). Daily zinc intake of boys and girls with calcium stones was 2 mg and 1.2 mg less, respectively, than the daily intake recommended by the Institute of Medicine. Odds of incident stones were reduced by 13% for every 1 mg increase in daily zinc intake (OR 0.87, 95% CI 0.75-0.99). There was an estimated 4.5 μg/dl increase in urine zinc for every 1 mg increase in dietary zinc (p = 0.009), with weak evidence of a smaller increase in urine zinc in cases than in controls (interaction p = 0.08).

CONCLUSIONS

Decreased dietary zinc intake was independently associated with incident calcium nephrolithiasis in this population of adolescents.

Vitamin D Intake and the Risk of Incident Kidney Stones

PURPOSE

Kidney stones are a common and painful condition. Longitudinal prospective studies on the association between the intake of vitamin D and the risk of incident kidney stones are lacking.

MATERIALS AND METHODS

We performed a prospective analysis of 193,551 participants in the Health Professionals Follow-up Study and Nurses' Health Study I and II. Participants were divided into categories of total (less than 100, 100 to 199, 200 to 399, 400 to 599, 600 to 999, 1,000 IU per day or greater) and supplemental (none, less than 400, 400 to 599, 600 to 999, 1,000 IU per day or greater) vitamin D intake. During a followup of 3,316,846 person-years there were 6,576 incident kidney stone events. Cox proportional hazards regression models were adjusted for age, body mass index, comorbidities, use of medications and intake of other nutrients.

RESULTS

After multivariate adjustment there was no statistically significant association between vitamin D intake and risk of stones in the HPFS (HR for 1,000 or greater vs less than 100 IU per day 1.08, 95% CI 0.80, 1.47, p for trend = 0.92) and the NHS I (HR 0.99, 95% CI 0.73, 1.35, p for trend = 0.70), whereas there was a suggestion of a higher risk in the NHS II (HR 1.18, 95% CI 0.94, 1.48, p for trend = 0.02). Similar results were found for supplemental vitamin D intake.

CONCLUSIONS

Vitamin D intake in typical amounts was not statistically associated with risk of kidney stone formation, although higher risk with higher doses than those studied here cannot be excluded.

Nephrolithiasis, bone mineral density, osteoporosis, and fractures: a systematic review and comparative meta-analysis

Our meta-analysis demonstrates that people with nephrolithiasis have decreased bone mineral density, an increased odds of osteoporosis, and potentially an elevated risk of fractures.

INTRODUCTION

People with nephrolithiasis might be at risk of reduced bone mineral density (BMD) and fractures, but the data is equivocal. We conducted a meta-analysis to investigate if patients with nephrolithiasis have worse bone health outcomes (BMD), osteoporosis, and fractures versus healthy controls (HCs).

METHODS

Two investigators searched major databases for articles reporting BMD (expressed as g/cm² or a T- or Z-score), osteoporosis or fractures in a sample of people with nephrolithiasis, and HCs. Standardized mean differences (SMDs), 95 % confidence intervals (CIs) were calculated for BMD parameters; in addition odds (ORs) for case-control and adjusted hazard ratios (HRs) in longitudinal studies for categorical variables were calculated.

RESULTS

From 1816 initial hits, 28 studies were included. A meta-analysis of case-control studies including 1595 patients with nephrolithiasis (mean age 41.1 years) versus 3402 HCs (mean age 40.2 years) was conducted. Patients with nephrolithiasis showed significant lower T-scores values for the spine (seven studies; SMD = -0.69; 95 % CI = -0.86 to -0.52; I ² = 0 %), total hip (seven studies; SMD = -0.82; 95 % CI = -1.11 to -0.52; I ² = 72 %), and femoral neck (six studies; SMD = -0.67; 95 % CI = --1.00 to -0.34; I ² = 69 %). A meta-analysis of the case-controlled studies suggests that people with nephrolithiasis are at increased risk of fractures (OR = 1.15, 95 % CI = 1.12-1.17, p < 0.0001, studies = 4), while the risk of fractures in two longitudinal studies demonstrated trend level significance (HR = 1.31, 95 % CI = 0.95-1.62). People with nephrolithiasis were four times more likely to have osteoporosis than HCs (OR = 4.12, p < 0.0001).

CONCLUSIONS

Nephrolithiasis is associated with lower BMD, an increased risk of osteoporosis, and possibly, fractures. Future screening/preventative interventions targeting bone health might be indicated.

Correlation of Osteoporosis and Calcium Urolithiasis in Adult Population

Introduction:

Scientific studies indicate that there is a correlation between decreased bone mineral density and the age of the patient, especially in post menopausal women.

Goal:

The aim of our study was to assess the connection between osteoporosis and the age of respondents, based on the DEXA findings in patients with calcium urolithiasis.

Material and methods:

The study was prospectively and conducted in University Clinical Center Banja Luka, at the Urology Clinic and Clinic of Internal Medicine. In this study the respondents were divided into two groups: experimental group–subjects with calcium urolithiasis and control group without calcium urolithiasis. The study included 240 patients, in both groups of 120 patients who were divided into three age groups: 20-40 years, 40-60 years and more than 60 years. In both groups of respondents was conducted determination of bone mineral density in L2-L4 vertebra lumbar spine and hip by DEXA method.

Results:

Observing the whole sample of the experimental group, according to age groups it can be noticed that DEXA results are at 72.5% normal, 27.5% below expected value, more in women within older subgroups, 20% show signs of osteopenia and osteoporosis in 7.5 %. Share of patients with osteoporosis is statistically different (p<0.05) only between sub-groups 20-40 years and over 60 years. Although appears absolute difference in the participation of patients with osteopenia by age groups, the differences are not statistically significant (p>0.05). The share of patients with normal DEXA values was significantly lower in the group over 60 years compared to the other two age groups (p<0.05). At age subgroups of the control group, the youngest group of respondents share with normal DEXA finding is 95% and among the oldest group (over 60 years) this share is much lower and is 60%, which represents a statistically significant difference, and confirms the relationship (p<0.01). Normal DEXA findings decreases with increasing years, the share of those who do not have normal findings is higher in the elderly population.

Conclusion:

Our study has just shown that in adult patients with calcium urolithiasis osteoporosis is more prevalent in older patients and more pronounced in patients with calcium urolithiasis in relation to the population without the same.

Calcium intake and urinary stone disease

Calcium homeostasis is a complicated and incompletely understood process that is primarily regulated through an interaction between the intestines, kidneys, and bones. Intestinal calcium absorption is determined by many factors including the amount of regular calcium intake, as well as vitamin D and parathyroid hormone levels. Intestinal calcium absorption is likely different between stone formers and non-stone formers, with higher levels of calcium absorption in those with a history of stones independent of their calcium intake. We no longer recommend dietary calcium restriction as this may lead to bone demineralization and an increase in stone formation. Practitioners need to continue to educate patients to maintain moderate dietary calcium intake. The effect of calcium supplementation on stone formation is currently controversial. It is likely that large doses of supplemental calcium, especially if taken separate from a meal, may lead to stone formation. When necessary, stone forming patients should be encouraged to take their calcium supplements with a meal and their stone disease should be monitored.

Nephrolithiasis and Risk of Incident Bone Fracture

PURPOSE

Higher urine calcium is a common feature of calcium nephrolithiasis and may be associated with lower bone mineral density in individuals with kidney stones. However previous population based studies of kidney stones and the risk of bone fracture demonstrate conflicting results. We examined independent associations between a history of kidney stones and incident fracture.

MATERIALS AND METHODS

We performed prospective studies using data from the Nurses' Health Study of 107,001 women with 32 years of followup and the Health Professionals Follow-up Study of 50,982 men with 26 years of followup. We excluded premenopausal women, men younger than 45 years and individuals who reported osteoporosis at baseline. Study outcomes were incident wrist (distal radius) or incident hip (proximal femur) fracture due to low or moderate trauma. Cox proportional hazards regression was used to adjust for multiple factors, including age, race, body mass index, thiazide use, supplemental calcium and dietary intakes.

RESULTS

There were 4,940 wrist and 2,391 hip fractures in women, and 862 wrist and 747 hip fractures in men. All fractures were incident. The multivariable adjusted relative risk of incident wrist fracture in participants with a history of kidney stones compared to participants without kidney stones was 1.18 (95% CI 1.04-1.34) in women and 1.21 (95% CI 1.00-1.47) in men. The pooled multivariable adjusted relative risk of wrist fracture was 1.20 (95% CI 1.08-1.33). The multivariable adjusted relative risk of incident hip fracture in participants with kidney stones was 0.96 (95% CI 0.80-1.14) in women and 0.92 (95% CI 0.74-1.14) in men. The pooled multivariable adjusted relative risk of hip fracture was 0.94 (95% CI 0.82-1.08).

CONCLUSIONS

Nephrolithiasis is associated with a significantly higher risk of incident wrist but not hip fracture in women and men.

Urinary Tract Stones and Osteoporosis: Findings From the Women's Health Initiative

Kidney and bladder stones (urinary tract stones) and osteoporosis are prevalent, serious conditions for postmenopausal women. Men with kidney stones are at increased risk of osteoporosis; however, the relationship of urinary tract stones to osteoporosis in postmenopausal women has not been established. The purpose of this study was to determine whether urinary tract stones are an independent risk factor for changes in bone mineral density (BMD) and incident fractures in women in the Women's Health Initiative (WHI). Data were obtained from 150,689 women in the Observational Study and Clinical Trials of the WHI with information on urinary tract stones status: 9856 of these women reported urinary tract stones at baseline and/or incident urinary tract stones during follow-up. Cox regression models were used to determine the association of urinary tract stones with incident fractures and linear mixed models were used to investigate the relationship of urinary tract stones with changes in BMD that occurred during WHI. Follow-up was over an average of 8 years. Models were adjusted for demographic and clinical factors, medication use, and dietary histories. In unadjusted models there was a significant association of urinary tract stones with incident total fractures (HR 1.10; 95% CI, 1.04 to 1.17). However, in covariate adjusted analyses, urinary tract stones were not significantly related to changes in BMD at any skeletal site or to incident fractures. In conclusion, urinary tract stones in postmenopausal women are not an independent risk factor for osteoporosis.

Modeling hypercalciuria in the genetic hypercalciuric stone-forming rat

PURPOSE OF REVIEW

In this review, we discuss how the genetic hypercalciuric stone-forming (GHS) rats, which closely model idiopathic hypercalciuria and stone formation in humans, provide insights into the pathophysiology and consequences of clinical hypercalciuria.

RECENT FINDINGS

Hypercalciuria in the GHS rats is due to a systemic dysregulation of calcium transport, as manifest by increased intestinal calcium absorption, increased bone resorption and decreased renal tubule calcium reabsorption. Increased levels of vitamin D receptor in intestine, bone and kidney appear to mediate these changes. The excess receptors are biologically active and increase tissue sensitivity to exogenous vitamin D. Bones of GHS rats have decreased bone mineral density (BMD) as compared with Sprague-Dawley rats, and exogenous 1,25(OH)2D3 exacerbates the loss of BMD. Thiazide diuretics improve the BMD in GHS rats.

SUMMARY

Studying GHS rats allows direct investigation of the effects of alterations in diet and utilization of pharmacologic therapy on hypercalciuria, urine supersaturation, stone formation and bone quality in ways that are not possible in humans.

Vascular Calcification and Stone Disease: A New Look towards the Mechanism

Calcium phosphate (CaP) crystals are formed in pathological calcification as well as during stone formation. Although there are several theories as to how these crystals can develop through the combined interactions of biochemical and biophysical factors, the exact mechanism of such mineralization is largely unknown. Based on the published scientific literature, we found that common factors can link the initial stages of stone formation and calcification in anatomically distal tissues and organs. For example, changes to the spatiotemporal conditions of the fluid flow in tubular structures may provide initial condition(s) for CaP crystal generation needed for stone formation. Additionally, recent evidence has provided a meaningful association between the active participation of proteins and transcription factors found in the bone forming (ossification) mechanism that are also involved in the early stages of kidney stone formation and arterial calcification. Our review will focus on three topics of discussion (physiological influences-calcium and phosphate concentration-and similarities to ossification, or bone formation) that may elucidate some commonality in the mechanisms of stone formation and calcification, and pave the way towards opening new avenues for further research.

Risk of fracture in urolithiasis: a population-based cohort study using the health improvement network

BACKGROUND AND OBJECTIVES

Studies have shown decreased bone mineral density in individuals with urolithiasis, but their burden of fracture remains unclear. This study sought to determine whether urolithiasis is associated with increased fracture risk across the lifespan and to delineate sex effects.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A population-based retrospective cohort study using The Health Improvement Network was performed. The median calendar year for the start of the observation period was 2004 (1994-2012). This study identified 51,785 participants with ≥1 of 87 diagnostic codes for urolithiasis and 517,267 randomly selected age-, sex-, and practice-matched participants. Cox regression was used to estimate the hazard ratio (HR) for first fracture. Fractures identified using diagnostic codes were classified by anatomic site.

RESULTS

Median age was 53 years, and 67% of participants were men, confirming their greater urolithiasis burden. Median time from urolithiasis diagnosis to fracture was 10 years. The HR for fracture associated with urolithiasis differed by sex and age (P for interactions, P≤0.003). In men, the adjusted HR was greatest in adolescence (1.55; 95% confidence interval [95% CI], 1.07 to 2.25) with an overall HR of 1.10 (95% CI, 1.05 to 1.16). Urolithiasis was associated with higher fracture risk in women aged 30-79 years (HR, 1.17-1.52), and was highest in women aged 30-39 years (HR, 1.52; 95% CI, 1.23 to 1.87). Peak background fracture rates were highest in boys aged 10-19 years and in women aged 70-79 years. The incidence per 10,000 person-years in participants with versus without urolithiasis was 392 versus 258 in male participants aged 10-19 years, and 263 versus 218 in women aged 70-79 years. Distribution of fracture site within sex did not differ between participants with versus without urolithiasis.

CONCLUSIONS

Urolithiasis was associated with higher incident fracture risk. The significantly higher risk at times of peak background fracture incidence in adolescent boys and elderly women has profound public health implications.

Incidence of osteoporosis in patients with urolithiasis

Introduction.

Clinical researches have shown an increased bone disintegration and lower bone mass in patients with calcium urolithiasis.

Goal.

The goal of our research was to establish the incidence of osteoporosis in adult patients with calcium urolithiasis, on the basis of measuring mineral bone density, using DEXA method, with a special reflection on age subgroups.

Material and methods.

Clinical research was prospective and it was implemented at the University Clinical Center of Banja Luka, at the Clinic for Endocrinology, Diabetes and Metabolic Diseases and at the Urology Clinic. Material in this research consisted of patients divided in two groups, a working and a control group. One hundred and twenty (120) patients were included in both these groups, divided in three age subgroups: 20-40, 40-60 and over 60. The working group consisted of the patients with calcium urolithiasis and the control group consisted of patients without calcium urolithiasis. Establishing of mineral bone density at L2-L4 of lumbal spine vertebrae and hip was done for the patients in both these groups, using DEXA method.

Results.

Analysis of mineral bone density using DEXA method in patients in age groups of working and control groups, as well as in the total sample of working and control groups, have shown that the patients of the working group, over 60, had a decreased mineral bone density (30% of osteopenia and 15% osteoporosis) significantly more expressed when compared to the other two age groups (12.5% in the subgroup 20-40 and 17.5% in the subgroup 40-60), which presents a statistically significant difference (p<0.05). In the control group, when taking into account age groups, osteopenia and osteoporosis were marked in 37.5% and 2.5% in the group of patients over 60, whereas in the youngest population, 5% of osteopenia was found, which presents a statistically significant difference (p<0.05). When observing the total sample of working and control group, there was a statistically significant difference in the working and control group (p<0.01); incidence of osteoporosis in the working group amounted to 7.5% and in the control group it was 0.8%.

Conclusion.

Urolithiasis and osteoporosis are two multifactorial diseases which are evidently reciprocal. This is why we suggest that educating the population about the risk factors for occurrence of these diseases as well as preventive measures that may contribute to their decrease should begin as early as possible.

Osteoporosis and the risk of symptomatic nephrolithiasis: a population-based 5-year follow-up study in Taiwan

This study estimates the risk of symptomatic nephrolithiasis within 5 years of newly diagnosed osteoporosis in a Taiwan population. This cohort study consisted of patients with a diagnosis of osteoporosis between Jan. 2003 and Dec. 2005 (N = 1634). Four age- and gender- matched patients for every patient in the study cohort were selected using random sampling as the comparison cohort (N = 6536). All patients were tracked for 5 years from the date of cohort entry to identify whether they developed symptomatic nephrolithiasis. Cox proportional hazard regressions were performed to evaluate the 5-year nephrolithiasis-free survival rates. During the 5-year follow-up period, 60 osteoporosis patients (3.7%) and 165 non- osteoporosis patients (2.5%) developed symptomatic nephrolithiasis. The adjusted HR of symptomatic nephrolithiasis was 1.38 times greater risk for patients with osteoporosis than for the comparison cohort (95% confidence interval (CI) 1.03-1.86; P < .05). Osteoporosis is very likely to be an independent risk factor for subsequent diagnosis of symptomatic nephrolithiasis.

Pediatric nephrolithiasis and the link to bone metabolism

PURPOSE OF REVIEW

To review the recent publications describing the link between pediatric nephrolithiasis and bone metabolism.

RECENT FINDINGS

Nephrolithiasis incidence is increasing in children and is associated with low bone mineral density (BMD). Affected children are conceptually at risk for fractures and osteoporosis. In addition to abnormal calcium metabolism, inflammation, genetic makeup and dietary habits are being recognized as important factors in the pathophysiology of nephrolithiasis and low bone density. Findings from retrospective reviews suggest that low BMD in children may be improved with citrate or thiazide treatment.

SUMMARY

The healthcare burden from low BMD with subsequent osteoporosis and fracture risk is immense with potential far-reaching effects in patient quality of life and healthcare expense. Bone mass is acquired in the pediatric age range, thus it is important to identify and treat at-risk children. Retrospective reviews in pediatric patients indicate that citrate or thiazide diuretic treatment may improve BMD. We now understand that a relationship exists between nephrolithiasis and low BMD. To improve healthcare for our current patients as well as protect their future health it is important to identify low BMD and initiate strategies to improve BMD in 'at-risk' children.

The relation between bone and stone formation

Hypercalciuria is the most common metabolic abnormality found in patients with calcium-containing kidney stones. Patients with hypercalciuria often excrete more calcium than they absorb, indicating a net loss of total-body calcium. The source of this additional urinary calcium is almost certainly the skeleton, the largest repository of calcium in the body. Hypercalciuric stone formers exhibit decreased bone mineral density (BMD), which is correlated with the increase in urine calcium excretion. The decreased BMD also correlates with an increase in markers of bone turnover as well as increased fractures. In humans, it is difficult to determine the cause of the decreased BMD in hypercalciuric stone formers. To study the effect of hypercalciuria on bone, we utilized our genetic hypercalciuric stone-forming (GHS) rats, which were developed through successive inbreeding of the most hypercalciuric Sprague-Dawley rats. GHS rats excrete significantly more urinary calcium than similarly fed controls, and all the GHS rats form kidney stones while control rats do not. The hypercalciuria is due to a systemic dysregulation of calcium homeostasis, with increased intestinal calcium absorption, enhanced bone mineral resorption, and decreased renal tubule calcium reabsorption associated with an increase in vitamin D receptors in all these target tissues. We recently found that GHS rats fed an ample calcium diet have reduced BMD and that their bones are more fracture-prone, indicating an intrinsic disorder of bone not secondary to diet. Using this model, we should better understand the pathogenesis of hypercalciuria and stone formation in humans to ultimately improve the bone health of patients with kidney stones.

Primary male osteoporosis is associated with enhanced glucocorticoid availability

OBJECTIVE

While systemic glucocorticoids compromise bone metabolism, altered intracellular cortisol availability may also contribute to the pathogenesis of primary male osteoporosis (MO). The objective of this study was to assess whether intracellular cortisol availability is increased in MO due to a distorted local cortisol metabolism.

METHODS

Forty-one patients with MO were compared with age- and BMI-matched non-osteoporotic subjects after excluding overt systemic hypercortisolism (N = 41). Cortisol, cortisone and the respective tetrahydro-, 5α-tetrahydro- and total cortisol metabolites were analysed by GC-MS in 24 h urine. Apparent 11β-hydroxysteroid dehydrogenase (11β-HSD) enzyme activities, excretion of cortisol metabolites and calcium, and fractional urinary calcium excretion were assessed and related to BMD.

RESULTS

Fractional and total urinary calcium excretion negatively correlated with BMD at all (P < 0.05) and at three of five (P < 0.05) measurement sites, respectively. While systemic cortisol was unchanged, apparent 11β-HSD enzyme activity in MO patients (P < 0.01) suggested increased intracellular cortisol availability. Total and fractional urinary calcium excretion was higher, with apparent 11β-HSD enzyme activities consistent with an enhanced intracellular cortisol availability (P < 0.05).

CONCLUSION

Apparent 11β-HSD enzyme activities consistent with increased intracellular cortisol availability correlated with urinary calcium loss and reduced bone mineral density in MO. The changes in 11β-HSD activity were associated with both the fractional calcium excretion, suggesting altered renal calcium handling, and the absolute urinary calcium excretion. Both mechanisms could result in a marked bone calcium deficiency if insufficiently compensated for by intestinal calcium uptake.

Calcium renal lithiasis and bone mineral density. Importance of bone metabolism in urinary lithiasis

CONTEXT

Calcium Nephrolithiasis is a multifactorial disease; in its pathophysiology is involved various minerals and metabolic factors that may be altered, including bone and phosphor-calcium metabolism.

OBJECTIVE

To establish the scientific evidence and demonstrate the relationship between calcium nephrolithiasis and bone mineral density loss, through the use of bone turnover markers, serum and urinary metabolites.

EVIDENCE ACQUISITION

We performed a PubMed literature review using different MeSH Terms like "Nephrolithiasis", "Bone mineral density", "Urinary stones", "Calcium", Bone resorption" and "Bone formation", with different combinations. We only selected articles with abstracts in English or Spanish and discarded clinical cases and articles with inappropriate statistical study. A total of 40 articles were selected.

EVIDENCE SYNTHESIS

In different studies reviewed have been observed that patients with hypercalciuria have a higher bone mineral density loss with respect to normocalciuric. Among patients with calcium stones (normocalciuric or hypercalciuric), there is loss of bone mineral density, being more evident in patients with stones and hypercalciuria. This mineral density loss is marked and important in patients with recurrent calcium stones. Increased markers like fasting calcium/creatinine and β-CrossLaps are determinant of nephrolithiasis and mineral density loss in these patients.

CONCLUSION

We recommend perform markers of bone turnover and fasting calcium/creatinine in patients with recurrent calcium stones by the significant presence of bone mineral density loss, with a level of evidence III.

Idiopathic hypercalciuria and bone health

Calcium is an important participant in many physiologic processes including coagulation, cell membrane transfer, hormone release, neuromuscular activation, and myocardial contraction. The body cooperates in a sophisticated web of hormonally mediated interactions to maintain stable extracellular calcium levels. Calcium is vital for skeletal mineralization, and perturbations in extracellular calcium may be corrected at the expense of bone strength and integrity. The aim of this review is to delineate our current understanding of idiopathic hypercalciuria in the context of bone health, specifically its definition, etiology, epidemiology, laboratory evaluation, and potential therapeutic management.

Biomolecular mechanism of urinary stone formation involving osteopontin

Urinary stones consist of two phases-an inorganic (mineral) phase and an organic (matrix) phase. Studies on the organic components of kidney stones have been undertaken later than those on the inorganic components. After osteopontin was identified as one of the matrix components, the biomolecular mechanism of urinary stone formation became clearer. It also triggered the development of new preventive treatments. Osteopontin expression is sporadically observed in normal distal tubular cells and is markedly increased in stone-forming kidneys. Calcium oxalate crystals adhering to renal tubular cells are incorporated into cells by the involvement of osteopontin. Stimulation of crystal-cell adhesion impairs the opening of mitochondrial permeability transition pores (mPTP) in tubular cells and produces oxidative stress, apoptosis, and osteopontin expression. Macrophages phagocytose and digest a small amount of crystals, but many crystals aggregate into a mass containing osteopontin and epithelial cell debris and are excreted into the renal tubular lumen, becoming nuclei of urinary stones. This biomolecular mechanism is similar to atherosclerotic calcification. Based on these findings, new preventive treatments have been developed. Dietary control such as low-cholesterol intake and the ingestion of antioxidative foods and vegetables have successfully reduced the 5-year recurrence rate. Osteopontin antibodies and cyclosporine A, which blocks the opening of mPTP, have markedly inhibited the expression of osteopontin and urinary stone formation in animal models.

Unrecognized and unappreciated secondary causes of osteoporosis

There are a substantial number of secondary causes of osteoporosis that can be identified through appropriate evaluation. Unrecognized celiac disease, Monoclonal gamopathy of undetermined significance (MGUS), impaired renal function, diabetes mellitus, and renal tubular acidosis are just a few of the more common secondary causes of osteoporosis. Through targeted laboratory tests, many secondary causes of osteoporosis can be identified.

Osteopenia/osteoporosis in patients with calcium nephrolithiasis

The objective of this study is to analyze the alterations in bone mineral density and bone and calcium-phosphorus metabolism in patients with calcium nephrolithiasis. We designed a study with 182 patients who were distributed among three groups: group O, 56 patients without nephrolithiasis; group A, 67 patients with calcium nephrolithiasis and mild lithogenic activity; and group B, 59 patients with calcium nephrolithiasis and severe lithogenic activity. Metabolic parameters of blood and urine that were related to calcium-phosphorous and bone metabolism and bone densitometry were assessed in all patients. A comparative study was performed on the variables of bone and calcium-phosphorus metabolism and bone densitometry as well as the presence or absence of osteopenia/osteoporosis. The patients in group B had a greater loss of bone mineral density, measured by the T-score, than the patients in groups O and A. Moreover, the proportion of patients in group B with osteopenia/osteoporosis was statistically significantly higher than the proportion of patients in groups O and A. We observed higher values of calciuria, fasting calcium/creatinine ratio, and 24-h calcium/creatinine among the patients in group B compared to the other two groups. Calciuria, citraturia, and fasting calcium/creatinine were independent factors that showed a relationship with severe lithogenic activity compared to the control group, and β-crosslaps is an independent factor that has a relationship with severe lithogenic activity as compared to mild lithogenic activity. Patients with calcium lithiasis and severe lithogenic activity have a greater loss in bone mineral density and therefore a greater risk of osteopenia/osteoporosis.

Prevalence and densitometric characteristics of incomplete distal renal tubular acidosis in men with recurrent calcium nephrolithiasis

The aim of this study was to assess the prevalence of incomplete distal renal tubular acidosis (idRTA) in men with recurrent calcium nephrolithiasis and its potential impact on bone mineral density. We conducted a retrospective analysis of 150 consecutive, male idiopathic recurrent calcium stone formers (RCSFs), which had originally been referred to the tertiary care stone center of the University Hospital of Berne for further metabolic evaluation. All RCSFs had been maintained on a free-choice diet while collecting two 24-h urine samples and delivered second morning urine samples after 12 h fasting. Among 12 RCSFs with a fasting urine pH >5.8, a modified 3-day ammonium chloride loading test identified idRTA in 10 patients (urine pH >5.32, idRTA group). We matched to each idRTA subject 5 control subjects from the 150 RCSFs, primary by BMI and then by age, i.e., 50 patients, without any acidification defect (non-RTA group) for comparative biochemistry and dual energy X-ray absorptiometry (DEXA) analyses. The prevalence of primary idRTA among RCSFs was 6.7% (10/150). Patients with idRTA had significantly higher 2-h fasting and 24-h urine pH (2-h urine pH: 6.6 ± 0.4 vs. 5.2 ± 0.1, p = 0.001; 24-h urine pH: 6.1 ± 0.2 vs. 5.3 ± 0.3, p = 0.001), 24-h urinary calcium excretion (7.70 ± 1.75 vs. 5.69 ± 1.73 mmol/d, p = 0.02), but significantly lower 24-h urinary urea excretion (323 ± 53 vs. 399 ± 114 mmol/d, p = 0.01), urinary citrate levels (2.32 ± 0.82 vs. 3.01 ± 0.72 mmol/d, p = 0.04) and renal phosphate threshold normalized for the glomerular filtration rate (TmPO(4)/GFR: 0.66 ± 0.17 vs. 0.82 ± 0.21, p = 0.03) compared to non-RTA patients. No significant difference in bone mineral density (BMD) was found between idRTA and non-RTA patients for the lumbar spine (LS BMD (g/cm(2)): 1.046 ± 0.245 SD vs. 1.005 ± 0.119 SD, p = 0.42) or femoral neck (FN BMD (g/cm(2)): 0.830 ± 0.135 SD vs. 0.852 ± 0.127 SD). Thus, idRTA occurs in 1 in 15 male RCSFs and should be sought in all recurrent calcium nephrolithiasis patients. Bone mineral density, however, does not appear to be significantly affected by idRTA.

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.

Bone disease and cytokines in idiopathic hypercalciuria: a review

Bone remodeling is a continuous and dynamic process of skeletal destruction and renewal. A complex regulatory mechanism with the participation of several cytokines precisely defines the role of osteoclasts in the chain of events leading to bone resorption. There are multiple mechanisms underlying the regulation of bone resorption, which can involve increased calcium excretion and decreased bone density in patients with idiopathic hypercalciuria (IH). However, the pathogenesis of bone mass reduction in IH remains uncertain. The purpose of this review is to summarize the recent published evidence on the possible mechanisms by which cytokines could be associated with the pathogenesis of IH.

Nephrolithiasis-associated bone disease: pathogenesis and treatment options

Nephrolithiasis remains a formidable health problem in the United States and worldwide. A very important but underaddressed area in nephrolithiasis is the accompanying bone disease. Epidemiologic studies have shown that osteoporotic fractures occur more frequently in patients with nephrolithiasis than in the general population. Decreased bone mineral density and defects in bone remodeling are commonly encountered in patients with calcium nephrolithiasis. The pathophysiologic connection of bone defects to kidney stones is unknown. Hypercalciuria and hypocitraturia are two important risk factors for stone disease, and treatments with thiazide diuretics and alkali, respectively, have been shown to be useful in preventing stone recurrence in small prospective trials. However, no studies have examined the efficacy of these agents or other therapies in preventing continued bone loss in calcium stone formers. This manuscript reviews the epidemiology, pathophysiology, and potential treatments of bone disease in patients with nephrolithiasis.

Tibial or hip BMD predict clinical fracture risk equally well: results from a prospective study in 700 elderly Swiss women

SUMMARY

In a randomly selected cohort of Swiss community-dwelling elderly women prospectively followed up for 2.8 +/- 0.6 years, clinical fractures were assessed twice yearly. Bone mineral density (BMD) measured at tibial diaphysis (T-DIA) and tibial epiphysis (T-EPI) using dual-energy X-ray absorptiometry (DXA) was shown to be a valid alternative to lumbar spine or hip BMD in predicting fractures.

INTRODUCTION

A study was carried out to determine whether BMD measurement at the distal tibia sites of T-EPI and T-DIA is predictive of clinical fracture risk.

METHODS

In a predefined representative cohort of Swiss community-dwelling elderly women aged 70-80 years included in the prospective, multi-centre Swiss Evaluation of the Methods of Measurement of Osteoporotic Fracture risk (SEMOF) study, fracture risk profile was assessed and BMD measured at the lumbar spine (LS), hip (HIP) and tibia (T-DIA and T-EPI) using DXA. Thereafter, clinical fractures were reported in a bi-yearly questionnaire.

RESULTS

During 1,786 women-years of follow-up, 68 clinical fragility fractures occurred in 61 women. Older age and previous fracture were identified as risk factors for the present fractures. A decrease of 1 standard deviation in BMD values yielded a 1.5-fold (HIP) to 1.8-fold (T-EPI) significant increase in clinical fragility fracture hazard ratio (adjusted for age and previous fracture). All measured sites had comparable performance for fracture prediction (area under the curve range from 0.63 [LS] to 0.68 [T-EPI]).

CONCLUSION

Fracture risk prediction with BMD measurements at T-DIA and T-EPI is a valid alternative to BMD measurements at LS or HIP for patients in whom these sites cannot be accessed for clinical, technical or practical reasons.

Genetic hypercalciuric stone-forming rats have a primary decrease in BMD and strength

Kidney stone patients often have a decrease in BMD. It is unclear if reduced BMD is caused by a primary disorder of bone or dietary factors. To study the independent effects of hypercalciuria on bone, we used genetic hypercalciuric stone-forming (GHS) rats. GHS and control (Ctl) rats were fed a low Ca (0.02% Ca, LCD) or a high Ca (1.2% Ca, HCD) diet for 6 wk in metabolic cages. All comparisons are to Ctl rats. Urine Ca was greater in the GHS rats on both diets. GHS fed HCD had reduced cortical (humerus) and trabecular (L(1)-L(5) vertebrae) BMD, whereas GHS rats fed LCD had a reduction in BMD similar to Ctl. GHS rats fed HCD had a decrease in trabecular volume and thickness, whereas LCD led to a approximately 20-fold increase in both osteoid surface and volume. GHS rats fed HCD had no change in vertebral strength (failure stress), ductibility (failure strain), stiffness (modulus), or toughness, whereas in the humerus, there was reduced ductibility and toughness and an increase in modulus, indicating that the defect in mechanical properties is mainly manifested in cortical, rather than trabecular, bone. GHS rat cortical bone is more mineralized than trabecular bone and LCD led to a decrease in the mineralization profile. Thus, the GHS rats, fed an ample Ca diet, have reduced BMD with reduced trabecular volume, mineralized volume, and thickness, and their bones are more brittle and fracture prone, indicating that GHS rats have an intrinsic disorder of bone that is not secondary to diet.

Bone disease and idiopathic hypercalciuria

Observational and epidemiologic studies alike have shown that idiopathic hypercalciuric (IH) stone-forming patients typically show bone mineral density scores that are significantly lower than those observed for age- and sex-matched normal subjects or those for nonhypercalciuric stone-forming patients. Most of these studies have relied on changes in bone mineral density and have not explored the mechanism(s) involved. There have been a small number of studies that have relied on dynamic bone histomorphometry to ascertain the nature of the bone defect in IH patients. When performed, these studies clearly have shown increased bone resorption and high bone turnover in patients with fasting hypercalciuria whereas suppressed bone formation indices are the most consistent finding in patients with the absorptive variant of IH. The causes of this apparent difference in bone remodeling between the 2 variants of IH still is uncertain. Available evidence suggests that potential mechanisms may be dependent in large part to genetic, metabolic, and nutritional causes of hypercalciuria and bone loss in patients with IH.

Urolithiasis in an acute lymphoblastic leukemia child during induction chemotherapy

An 11-year-old acute lymphoblastic leukemia patient suddenly developed severe abdominal flank pain and hematuria caused by renal stone during induction chemotherapy. The patient was treated with forced hydration, and the pain was relieved after the renal stone passed through. The renal stone was composed of calcium phosphate. The patient is currently in continuous complete remission, has had no recurrence of the urolithiasis, and is on consolidation chemotherapy. Although urolithiasis is extremely rare in childhood acute lymphoblastic leukemia, it should be considered in patients who complain of abdominal flank pain or back pain during chemotherapy.

Renal stone disease: Causes, evaluation and medical treatment

The purpose of the present review is to provide an update about the most common risk factors or medical conditions associated with renal stone formation, the current methods available for metabolic investigation, dietary recommendations and medical treatment. Laboratory investigation of hypercalciuria, hyperuricosuria, hyperoxaluria, cystinuria, hypocitraturia, renal tubular acidosis, urinary tract infection and reduction of urinary volume is based on the results of 24-hr urine collection and a spot urine for urinary sediment, culture and pH. Blood analysis for creatinine, calcium and uric acid must be obtained. Bone mineral density has to be determined mainly among hypercalciurics and primary hyperparathyroidism has to be ruled out. Current knowledge does not support calcium restriction recommendation because it can lead to secondary hyperoxaluria and bone demineralization. Reduction of animal protein and salt intake, higher fluid intake and potassium consumption should be implemented. Medical treatments involve the use of thiazides, allopurinol, potassium citrate or other drugs according to the metabolic disturbances. The correction of those metabolic abnormalities is the basic tool for prevention or reduction of recurrent stone formation.

Blood pressure and calcium intake are related tobone density in adult males

Based on the premise that elevated blood pressure and low bone mass have both been associated with poor Ca nutriture and disturbances in Ca metabolism, a cross-sectional study was employed to determine if blood pressure and dietary Ca intake were significantly related to bone mass. Forty-seven men between 24–77 years of age with blood pressure values ranging from normal to mildly elevated comprised the study group. Blood pressure was measured with a random-zero sphygmomanometer. Bone mineral content (BMC) and density (BMD) of the hip, spine and total body were measured with dual-photon absorptiometry. Dietary intake and physical activity were also assessed. Multiple linear regression analysis was used for statistical analysis. After adjusting for known confounding variables (age, BMI, Ca intake, and others) diastolic blood pressure was negatively related to BMC (P ≤ 0·05) and BMD (P ≤ 0·01) of the total body, trochanteric region (P < 0·01) and Ward's triangle (P < 0·05), and to BMC of the femoral neck (P < 0·05) and lumbar spine, although the latter was just shy of statistical significance (P = 0·058). Systolic blood pressure was negatively related to trochanteric BMD (P = 0·04) and BMC (P = 0·06). Ca intake was positively related to total body BMD (P = 0·005), and BMC of the lumbar spine (P = 0·05). In this population of men, Ca intake was a positive predictor, and blood pressure was a negative predictor of regional measures of bone mass. These findings support the concept that independent of age, BMI and Ca intake, elevated blood pressure varies indirectly with bone mass and density, known predictors of osteoporotic fractures. Future studies are needed to determine whether elevated blood pressure is causally related to the development of low bone mass, and what role dietary Ca plays in that pathway.