Association between Circulating Vitamin D Level and Urolithiasis: A Systematic Review and Meta-Analysis

Relationship between remnant cholesterol and risk of kidney stones in U.S. Adults: a 2007-2016 NHANES analysis

PURPOSE

Remnant cholesterol (RC) is the cholesterol content of triglyceride-rich lipoproteins. This study aimed to investigate the association between RC levels and kidney stones in U.S. adults.

METHODS

Data were obtained from the 2007 to 2016 National Health and Nutrition Examination Survey (NHANES). A total of 10,551 participants with complete data were included and analyzed in this study. Univariate and multivariate logistic regression analysis, restricted cubic spline function, subgroup analysis and mediation analysis were preformed to estimate the independent relationship between RC levels and kidney stones.

RESULTS

Participants with stone formation had higher levels of RC than those with without stone formation (25.78 ± 13.83 vs 23.27 ± 13.04, p< 0.001). The results of logistic regression analysis and dose-response risk curves revealed a positive nonlinear association between RC levels and risk of kidney stones [univariate: adjusted odds ratio (aOR) =2.388, 95% CI: 1.797-3.173, p< 0.001; multivariate: aOR = 1.424, 95% CI: 1.050-1.929, p = 0.023]. Compared with the discordantly low RC group, the discordantly high RC group was associated with increased risk of kidney stones (aOR = 1.185, 95% CI: 1.013-1.386, p= 0.034). Similar results were demonstrated according to the discordance of different clinical cut points. And metabolic syndrome parameters and vitamin D levels parallelly mediated the association between RC and kidney stone risk.

CONCLUSIONS

Higher RC levels were independently associated with an increased risk of kidney stone incidence.

Association between serum 25-hydroxyvitamin D concentrations and kidney stone: a cohort study in the UK Biobank

OBJECTIVE

To investigate the association between serum 25(OH)D and kidney stone disease (KSD) in participants from the UK Biobank.

METHODS

We used data from the UK Biobank. Our analysis involved Cox proportional hazards models to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) to estimate the association between serum 25(OH)D levels (measured at the time of recruitment) and the risk of KSD, which was determined using hospital records.

RESULTS

This study involved 444,343 participants, with 4,458 cases of KSD identified during an average follow-up period of 12.6 years. Higher 25(OH)D levels were not associated with developing kidney stones in general population model 3 (HR = 0.88 [95% CI 0.77-1.01]). Interestingly, higher serum 25(OH)D concentrations in women over 60 years old were associated with a lower risk of kidney stone disease. The multivariate HRs and 95% CIs for participants who had serum 25(OH)D ≥ 50 nmol/L or ≥ 75 nmol/L, compared with those who were severely deficient (25[OH]D < 25 nmol/L), were 0.74 (0.58-0.95), 0.60 (0.43-0.85) for KSD, respectively (P for trend < 0.01). However, this trend was not statistically significant in the subgroup analysis of serum calcium ion concentration.

CONCLUSION

High 25(OH)D levels were not associated with a higher incidence of kidney stones if serum calcium levels are within a normal range. The findings alleviate physiological concerns regarding the supplementation of vitamin D alone to raise serum 25(OH)D concentration.

Diet-induced nephrocalcinosis in aquarium-raised juvenile spotted wolffish Anarhichas minor

Wolffish are regularly housed in aquaria, but little data on their husbandry and health is available for caretakers. High occurrence rates of nephrocalcinosis and urolithiasis have been observed in Atlantic Anarhichas lupus and spotted A. minor wolffish housed at 2 Canadian zoological institutions. To explore the effect of diet on nephrocalcinosis and urolithiasis development, a 16 mo prospective study was conducted. A total of 32 juvenile spotted wolffish were randomly assigned to one of 4 experimental groups fed exclusively with the following diet: (1) Skretting® Europa 18 pellets; (2) Mazuri® LS Aquatic Carni-Blend Diet Formula; (3) vitamin-supplemented fish-based diet, and (4) vitamin-supplemented invertebrate-based diet. Urinalysis, radiographs, and complete necropsies were performed at the end of the study. None of the wolffish developed uroliths during the study period. All specimens fed with the fish-based and invertebrate-based diets developed nephrocalcinosis, whereas this condition was seen in 12.5 and 0% of the fish in the Skretting® and Mazuri® groups, respectively. Affected wolffish often presented with oxalate crystalluria and increased radiodensity of the posterior kidneys. Urinalysis and radiographic study were considered useful in the antemortem diagnosis of nephrocalcinosis. None of the previously published risk factors for the development of nephrocalcinosis in fish were supported by the results of this study. However, nutritional analyses of the 4 diets suggest that high dietary levels of gelatin or vitamin C or low levels of vitamin E could be potential risk factors for the development of nephrocalcinosis in spotted wolffish and thus warrant further study.

Genes polymorphism as risk factor of recurrent urolithiasis: a systematic review and meta-analysis

INTRODUCTION

Urolithiasis is one of the most prevalent diseases worldwide. Its prevalence is rising, both in developing and developed countries. It is known that genetic factors play big roles in the development of urolithiasis. One of the suspected factors is gene polymorphism. This study aims to find an accurate estimate of the association between genetic polymorphism and the risk of recurrent urolithiasis.

METHODS

A systematic review and meta-analysis were performed on 12 studies from 3 databases that investigated gene polymorphism as an risk factor of urolithiasis. The review was done using Review Manager® version 5.3.

RESULTS

Insignificant heterogenicity was found in this study. Populations from Asia and the Middle East are more likely to experience recurrent urolithiasis. Additionally, variation in the VDR and urokinase genes, particularly in the Asian population, increases the risk of developing recurrent urolithiasis.

CONCLUSIONS

Gene polymorphisms have significant roles in the development of urolithiasis, especially in the Middle Eastern region.

Vitamins as regulators of calcium-containing kidney stones - new perspectives on the role of the gut microbiome

Calcium-based kidney stone disease is a highly prevalent and morbid condition, with an often complicated and multifactorial aetiology. An abundance of research on the role of specific vitamins (B6, C and D) in stone formation exists, but no consensus has been reached on how these vitamins influence stone disease. As a consequence of emerging research on the role of the gut microbiota in urolithiasis, previous notions on the contribution of these vitamins to urolithiasis are being reconsidered in the field, and investigation into previously overlooked vitamins (A, E and K) was expanded. Understanding how the microbiota influences host vitamin regulation could help to determine the role of vitamins in stone disease.

Lifestyle factors, serum parameters, metabolic comorbidities, and the risk of kidney stones: a Mendelian randomization study

Background and objective

The early identification of modifiable risk factors is important for preventing kidney stones but determining causal associations can be difficult with epidemiological data. We aimed to genetically assess the causality between modifiable factors (lifestyle factors, serum parameters, and metabolic comorbidities) and the risk of kidney stones. Additionally, we aimed to explore the causal impact of education on kidney stones and its potential mediating pathways.

Methods

We conducted a two-sample Mendelian randomization (MR) study to explore the causal association between 44 modifiable risk factors and kidney stones. The FinnGen dataset initially explored the causal relationship of risk factors with kidney stones and the UK Biobank dataset was used as the validation set. Then, a meta-analysis was conducted by combining discovery and validation datasets. We used two-step MR to assess potential mediators and their mediation proportions between education and kidney stones.

Results

The combined results indicated that previous exposures may increase the risk of kidney stones, including sedentary behavior, urinary sodium, the urinary sodium/potassium ratio, the urinary sodium/creatinine ratio, serum calcium, 25-hydroxyvitamin D (25OHD), the estimated creatinine-based glomerular filtration rate (eGFRcrea), GFR estimated by serum cystatin C (eGFRcys), body mass index (BMI), waist circumference, type 2 diabetes mellitus (T2DM), fasting insulin, glycated hemoglobin, and hypertension. Coffee intake, plasma caffeine levels, educational attainment, and the urinary potassium/creatinine ratio may decrease the risk of kidney stones. Ranked by mediation proportion, the effect of education on the risk of kidney stones was mediated by five modifiable risk factors, including sedentary behavior (mediation proportion, 25.7%), smoking initiation (10.2%), BMI (8.2%), T2DM (5.8%), and waist circumference (3.2%).

Conclusion

This study provides MR evidence supporting causal associations of many modifiable risk factors with kidney stones. Sedentary lifestyles, obesity, smoking, and T2DM are mediating factors in the causal relationship between educational attainment and kidney stones. Our results suggest more attention should be paid to these modifiable factors to prevent kidney stones.

Scientific opinion on the tolerable upper intake level for vitamin D, including the derivation of a conversion factor for calcidiol monohydrate

Following two requests from the European Commission (EC), the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver a scientific opinion on the revision of the tolerable upper intake level (UL) for vitamin D and to propose a conversion factor (CF) for calcidiol monohydrate into vitamin D3 for labelling purposes. Vitamin D refers to ergocalciferol (vitamin D2), cholecalciferol (vitamin D3), and calcidiol monohydrate. Systematic reviews of the literature were conducted to assess the relative bioavailability of calcidiol monohydrate versus vitamin D3 on serum 25(OH)D concentrations, and for priority adverse health effects of excess vitamin D intake, namely persistent hypercalcaemia/hypercalciuria and endpoints related to musculoskeletal health (i.e. falls, bone fractures, bone mass/density and indices thereof). Based on the available evidence, the Panel proposes a CF for calcidiol monohydrates of 2.5 for labelling purposes. Persistent hypercalciuria, which may be an earlier sign of excess vitamin D than persistent hypercalcaemia, is selected as the critical endpoint on which to base the UL for vitamin D. A lowest-observed-adverse-effect-level (LOAEL) of 250 μg/day is identified from two randomised controlled trials in humans, to which an uncertainty factor of 2.5 is applied to account for the absence of a no-observed-adverse-effect-level (NOAEL). A UL of 100 μg vitamin D equivalents (VDE)/day is established for adults (including pregnant and lactating women) and for adolescents aged 11-17 years, as there is no reason to believe that adolescents in the phase of rapid bone formation and growth have a lower tolerance for vitamin D compared to adults. For children aged 1-10 years, a UL of 50 μg VDE/day is established by considering their smaller body size. Based on available intake data, European populations are unlikely to exceed the UL, except for regular users of food supplements containing high doses of vitamin D.

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.

The influence of climatic factors in the seasonal fluctuation of urolithiasis and the trend of stone disease management in the southern Taiwan

This study aims to analyze the effects of climate parameters on the number of urolithiasis treatments in our hospital and understand the effects of climate parameters on the prevalence of urolithiasis in southern Taiwan. We also look at trends associated with urolithiasis and treatments. Retrospectively reviewed the records of extracorporeal shockwave lithotripsy (ESWL), ureteroscopy (URS), retrograde intrarenal surgery (RIRS), and percutaneous nephrolithotripsy (PCNL) performed in our hospital from January 2012 to December 2018. Climate data for were collected from Central Weather Bureau. The monthly meteorological data included average temperatures, humidity, rainfall, sunshine hours, atmospheric pressure, and wind speed. Monthly numbers of patients undergoing stone management was positively correlated to average temperature (r = 0.657), relative humidity (r = 0.234), monthly rainfall (r = 0.261) and monthly sunshine hours (r = 0.348), while it was negatively correlated to atmospheric pressure (r = - 0.522). The multivariate linear regression model demonstrated temperature (ß = 10.682, 95% CI 6.178-14.646, p < 0.001) and Relative humidity (ß = - 95% CI - 5.233- - 1.216, p = 0.002) to be independently related to numbers of stone treatment. The data also revealed a rising prevalence of urolithiasis with an associated increase in the number of interventions, with fewer ESWL (74.0-49.4%). Temperature and relative humidity are associated with monthly numbers of stone treatment. Ambient temperature is the most critical climate factor affecting the prevalence of symptomatic urolithiasis and intention of active stone removal in southern Taiwan.

A path analysis to investigate the interaction between serum, urinary and demographic factors influencing urine calcium in kidney stone formers

BACKGROUND

Hypercalciuria is one of the most important urinary risk factors in kidney stone formers. This study aimed to delineate the interaction of some demographic, serum, and urinary risk factors influencing 24-h urinary (24-U) calcium excretion.

METHODS

This study was secondary data analysis, using data from 593 kidney stone patients referred to the Labbafinejad kidney stone prevention clinic from March 2015 to May 2019. The study considered serum, urinary and demographic factors that interact to influence 24-U calcium using path analysis. In addition to the direct impact of predictors on the 24-U calcium, this analysis considered the effects of the predictors on the 24-U calcium transmitted by a mediating variable named indirect effects.

RESULTS

The results showed that age indirectly affected on 24-U calcium through 25-hydroxy vitamin D (25(OH)D), serum and 24-U creatinine. As well, weight had an indirect effect through 24-urine metabolites (creatinine, citrate, urea, and sodium). Among serum variables, PTH and creatinine significantly directly affected on 24-U calcium. In comparison, 25(OH)D and phosphorus appeared to influence 24-U calcium indirectly through serum parathormone. Regarding 24-U metabolites, sodium, urea, and citrate had a significant direct effect on 24-U calcium. Moreover, 24-U creatinine has a significant direct and indirect effect on 24-U calcium through citrate and urea as mediator variables.

CONCLUSION

Serum 25(OH)D and phosphorus, along with age and weight, indirectly affected urinary calcium through a third variable. Other variables (PTH, serum creatinine, and 24-U sodium, urea, and citrate) showed a direct effect on 24-U calcium excretion.

Association of hypercalciuria with vitamin D supplementation in patients undergoing ketogenic dietary therapy

Background

Ketogenic dietary therapy (KDT) is used as an effective treatment for epilepsy. However, KDT carries the risk of bone health deterioration; therefore, vitamin D supplementation is required. Vitamin D replacement therapy in KDT has not been established because it may be related to hypercalciuria/urolithiasis, which are common adverse effects of KDT. Hence, this study aimed to evaluate the dose-dependent association between vitamin D₃ and hypercalciuria/urolithiasis in patients undergoing KDT and dose optimization for renal complications.

Materials and methods

Overall, 140 patients with intractable childhood epilepsy started 3:1 KDT (lipid to non-lipid ratio) at the Severance Children’s Hospital from January 2016 to December 2019. Regular visits were recommended after KDT initiation. Participants were assessed for height, weight, serum 25-hydroxyvitamin D (25-OH-D₃) level, parathyroid hormone level, and ratio of urinary excretion of calcium and creatinine (Uca/Ucr). Kidney sonography was conducted annually. Patients who already had urolithiasis and were taking hydrochlorothiazide before KDT, failed to maintain KDT for 3 months, did not visit the pediatric endocrine department regularly, did not take prescribed calcium and vitamin D3 properly, or needed hospitalization for > 1°month because of serious medical illness were excluded. Data from patients who started diuretic agents, e.g., hydrochlorothiazide, were excluded from that point because the excretion of calcium in the urine may be altered in these patients.

Result

In total, 49 patients were included in this study. Uca/Ucr ratio significantly decreased with increasing levels of 25-OH-D₃ (p = 0.027). The odds ratio for hypercalciuria was 0.945 (95% confidence interval, 0.912–0.979; p = 0.002) per 1.0 ng/mL increment in 25-OH-D₃ level. Based on findings of receiver operating characteristic curve analysis and Youden’s J statistic, the cut-off 25-OH-D₃ level for preventing hypercalciuria was > 39.1 ng/mL at 6 months. Furthermore, the vitamin D₃ supplementation dose cut-off was > 49.5 IU/kg for hypercalciuria prevention.

Conclusion

An inverse relationship between Uca/Ucr ratio and 25-OH-D₃ level was noted, which means that vitamin D supplementation is helpful for preventing hypercalciuria related to KDT. We suggest that the recommended 25-OH-D₃ level is > 40 ng/mL for hypercalciuria prevention and that KDT for children with epilepsy can be optimized by vitamin D₃ supplementation at 50 IU/kg.

Genetically Predicted Lifelong Circulating 25(OH)D Levels are Associated With Serum Calcium Levels and Kidney Stone Risk

OBJECTIVE

To assess whether lifelong higher circulating 25-hydroxyvitamin D [25(OH)D] levels increase serum calcium levels and kidney stone disease (KSD) risk.

METHODS

Summary data for KSD were obtained from the UK biobank genome-wide association study (6536 cases and 388 508 controls). We acquired summary data for 25(OH)D from 120 618 Europeans and another large-scale analysis (443 734 Europeans) for primary and secondary analysis. Random-effect inverse-variance weighted (IVW) and 7 additional sensitivity analyses were applied. Next, multivariable Mendelian randomization (MVMR) was performed by introducing data for serum calcium levels.

RESULTS

Genetic predisposition for a 1-SD higher 25(OH)D level was associated with increased serum calcium levels (IVW; beta, 0.014; 95% CI, 0.010-0.018; P = 7.64E-10). Genetically predicted higher circulating 25(OH)D levels were associated with increased the risk of KSD, with per 1-SD odds ratios (ORs) of 1.47 (95% CI, 1.22-1.77; P = 5.49E-05) and 1.36 (95% CI, 1.03-1.80; P = 0.029) using the IVW and MVMR-Egger methods, respectively. In secondary analysis, similar results were found: 25(OH)D was associated with an increased risk of KSD in univariate Mendelian randomization (IVW; OR 1.71; 95% CI, 1.26-2.32; P = 0.001) and MVMR (OR 1.43; 95% CI, 1.16-1.76; P < 0.001) analyses. Most sensitivity analyses were consistent with the primary results, both for the primary and secondary analyses.

CONCLUSIONS

Our study supports that higher genetically predicted lifelong circulating 25(OH)D levels are associated with higher calcium levels and KSD risk. The effects of 25(OH)D on KSD were partially attenuated-but still significant-in MVMR.

A Phase II Multicenter Trial on High-Dose Vitamin D Supplementation for the Correction of Vitamin D Insufficiency in Patients with Breast Cancer Receiving Adjuvant Chemotherapy

Breast cancer (BC) treatments induce vitamin D (VD) insufficiency and bone metabolism changes, resulting in osteoporosis and skeletal morbidity risk. We report the results of a bicentric phase II trial (ClinicalTrials.gov Identifier: NCT04091178) on the safety and efficacy of high-dose oral VD supplementation for VD deficiency correction in 44 patients with early BC treated with adjuvant chemotherapies. Patients received one dose of 100,000 IU 25-OH VD every 3 weeks from day 1 of cycle 1 to day 1 of cycle 5. The primary endpoint was the percentage of patients achieving serum 25-OH VD concentration normalization on day 1 of cycle 6 (D1C6). Secondary endpoints were safety, VD and calcium parameters at baseline and during chemotherapy, and identification of predictive biomarkers of VD normalization on D1C6. On D1C6, 21 patients (47.7%, 95% CI: 33.0–62.8) achieved VD normalization. No VD-related clinical toxicity was reported. However, 13 patients (29.5%) presented asymptomatic grade 1 hypercalciuria, leading to interruption of the high-dose oral VD supplementation in 10, followed by a rapid reduction in serum VD concentration. No baseline clinical factor was predictive of VD normalization on D1C6. This high-dose VD supplementation appears safe and efficient in patients with early BC receiving adjuvant chemotherapy.

Calcium and Vitamin D Supplementation and Their Association with Kidney Stone Disease: A Narrative Review

Kidney stone disease is a multifactorial condition influenced by both genetic predisposition and environmental factors such as lifestyle and dietary habits. Although different monogenic polymorphisms have been proposed as playing a causal role for calcium nephrolithiasis, the prevalence of these mutations in the general population and their complete pathogenetic pathway is yet to be determined. General dietary advice for kidney stone formers includes elevated fluid intake, dietary restriction of sodium and animal proteins, avoidance of a low calcium diet, maintenance of a normal body mass index, and elevated intake of vegetables and fibers. Thus, balanced calcium consumption protects against the risk for kidney stones by reducing intestinal oxalate availability and its urinary excretion. However, calcium supplementation given between meals might increase urinary calcium excretion without the beneficial effect on oxalate. In kidney stone formers, circulating active vitamin D has been found to be increased, whereas higher plasma 25-hydroxycholecalciferol seems to be present only in hypercalciuric patients. The association between nutritional vitamin D supplements and the risk for stone formation is currently not completely understood. However, taken together, available evidence might suggest that vitamin D administration worsens the risk for stone formation in patients predisposed to hypercalciuria. In this review, we analyzed and discussed available literature on the effect of calcium and vitamin D supplementation on the risk for kidney stone formation.

Switching from conventional therapy to burosumab injection has the potential to prevent nephrocalcinosis in patients with X-linked hypophosphatemic rickets

OBJECTIVES

X-linked hypophosphatemic rickets (XLH) is a congenital fibroblast growth factor (FGF)23-related metabolic bone disease that is treated with active vitamin D and phosphate as conventional therapies. Complications of these therapies include nephrocalcinosis (NC) caused by excessive urine calcium and phosphate concentrations. Recently, an anti-FGF23 antibody, burosumab, was developed and reported to be effective in poorly-controlled or severe XLH patients. This study aimed to reveal the impact of switching treatments in relatively well-controlled XLH children with the Rickets Severity Scale less than 2.0.

METHODS

The effects of the two treatments in eight relatively well-controlled XLH children with a mean age of 10.4 ± 1.9 years were compared retrospectively for the same treatment duration (31 ± 11 months) before and after the baseline.

RESULTS

Actual doses of alfacalcidol and phosphate as conventional therapy were 150.9 ± 43.9 ng/kg and 27.5 ± 6.3 mg/kg per day, respectively. Renal echography revealed spotty NC in 8/8 patients, but no aggravation of NC was detected by switching treatments. Switching treatments increased TmP/GFR (p=0.002) and %TRP (p<0.001), and improved the high urine calcium/creatinine ratio to the normal range (p<0.001) although both treatments controlled disease markers equally. Additionally, low intact parathyroid hormone during conventional therapy was increased within the normal range by switching treatments.

CONCLUSIONS

Our results suggest that a high dose of alfacalcidol was needed to control the disease, but it caused hypercalciuria and NC. We concluded that switching treatments in relatively well-controlled XLH children improved renal phosphate reabsorption and decreased urine calcium extraction, and may have the potential to prevent NC.

Prevalence of Vitamin D Inadequacy in Urolithiasis Patients

Introduction

The role of vitamin D in kidney stone disease is unclear. Current evidence and existing studies are inconsistent and inconclusive. The objective of this study is to assess the prevalence of vitamin D (VD) inadequacy (VDI) and metabolic abnormalities in urolithiasis patients presenting to a tertiary care center.

Materials and methods

This is a prospective case-control study of 200 patients divided into two groups - Group 1: 100 urolithiasis patients (case group), and Group 2: 100 non-urolithiasis patients (control group) - which was conducted from January 2016 to January 2017. Demographic, clinical data, parathyroid level, serum 25-hydroxy VD [25(OH)D], and metabolic stone work-up were recorded and analyzed. 

Results

Patient demographics were comparable in both groups. The prevalence of vitamin D inadequacy in urolithiasis patients was 95% as compared to 57% in the control group. The mean value ± SD of serum vitamin D in urolithiasis patients (16.5 ± 8.6 ng/mL) was significantly lower than in non-urolithiasis patients (28.7 ± 8.3 ng/mL) (p = <0.0001). Thirty-seven percent of the patients were recurrent stone formers. Hyperparathyroidism was observed in 77% of the patients and 71% of them were secondary to VDI.

Conclusion

Urolithiasis patients were found to have an increased prevalence of deficient VD related to secondary hyperparathyroidism.

Obstructive urolithiasis in buffalo calves (Bubalus bubalis): Serum changes of Vitamins A and D and efficacy of surgical management using tube cystostomy

Background and Aim:

Obstructive urolithiasis is one of the major health problems in livestock animals, mainly in young calves. The present study was designed first to investigate the changes in the serum levels of Vitamins A and D in buffalo calves (Bubalus bubalis) with obstructive urolithiasis and second to investigate the efficacy of tube cystostomy technique in management of such condition.

Materials and Methods:

One hundred and forty-nine buffalo calves of variable ages ranged from 3 to 7 months with a history of retained urine were examined clinically and ultrasonographically. Then, they were subjected to surgical treatment using the tube cystostomy technique. The serum levels of Vitamins A and D were investigated in retained urine calves in addition to 10 clinically healthy calves of the same age used as a control group.

Results:

Based on clinical and ultrasonographic findings, the calves were diagnosed as obstructive urolithiasis with intact bladder (n=64 calves) or with bladder rupture (n=85 calves) with the peak incidence in winter months. Tube cystostomy was an efficient and quick surgical technique for the management of such condition and 95.3% of calves returned their normal urination within 7–14 days after surgery. Significant hypovitaminoses A and D were found between retained urine calves and control ones (p= 0.01 and 0.002, respectively).

Conclusion:

Hypovitaminoses A and D suggested predisposing obstructive urolithiasis in buffalo calves, but further clinical studies are recommended for more confirmation. Surgical treatment using tube cystostomy technique is recommended for the management of obstructive urolithiasis in buffalo calves.

Effect of Fat-Soluble Vitamins A, D, E and K on Vitamin Status and Metabolic Profile in Patients with Fat Malabsorption with and without Urolithiasis

Patients with intestinal fat malabsorption and urolithiasis are particularly at risk of acquiring fat-soluble vitamin deficiencies. The aim of the study was to evaluate the vitamin status and metabolic profile before and after the supplementation of fat-soluble vitamins A, D, E and K (ADEK) in 51 patients with fat malabsorption due to different intestinal diseases both with and without urolithiasis. Anthropometric, clinical, blood and 24-h urinary parameters and dietary intake were assessed at baseline and after ADEK supplementation for two weeks. At baseline, serum aspartate aminotransferase (AST) activity was higher in stone formers (SF; n = 10) than in non-stone formers (NSF; n = 41) but decreased significantly in SF patients after supplementation. Plasma vitamin D and E concentrations increased significantly and to a similar extent in both groups during intervention. While plasma vitamin D concentrations did not differ between the groups, vitamin E concentrations were significantly lower in the SF group than the NSF group before and after ADEK supplementation. Although vitamin D concentration increased significantly in both groups, urinary calcium excretion was not affected by ADEK supplementation. The decline in plasma AST activity in patients with urolithiasis might be attributed to the supplementation of ADEK. Patients with fat malabsorption may benefit from the supplementation of fat-soluble vitamins ADEK.

Vitamin D and Kidney Stones

This review explores the relationship between vitamin D supplementation and lithogenesis. A causal relationship has been assumed despite myriad studies demonstrating that therapeutic doses of vitamin D do not increase lithogenic risk. Select stone formers may be at increased risk for recurrence with vitamin D supplementation, possibly from CYP24A1 gene mutations. Additionally, the evidence for who is vitamin D deficient, and the benefits of supplementation in those not at risk for rickets, is sparse. Concerns may be avoidable as vitamin D screening appears unnecessary in most patients, and superior pharmacology is available which increases bone density, while decreasing stone formation.

Elevated Levels of 1,25-Dihydroxyvitamin D in Plasma as a Missing Risk Factor for Celiac Disease

The prevalence of celiac disease (CD) has increased significantly in some developed countries in recent decades. Potential risk factors that have been considered in the literature do not appear to provide a convincing explanation for this increase. This has led some researchers to hypothesize that there is a "missing environmental factor" that increases the risk of CD. Based on evidence from the literature, the author proposes that elevation in plasma levels of 1,25-dihydroxyvitamin D [1,25(OH)₂D] is a missing risk factor for CD, and relatedly that significant oral vitamin D exposure is a "missing environmental factor" for CD. First, elevated plasma levels of 1,25(OH)₂D are common in CD, especially in the newly diagnosed. Second, nine distinct conditions that increase plasma levels of 1,25(OH)₂D are either associated with CD or have indications of such an association in the literature. Third, a retrospective study shows that sustained oral vitamin D supplementation in infancy is associated with increased CD risk, and other studies on comorbid conditions support this association. Fourth, large doses of oral vitamin D upregulate many of the same cytokines, chemokines, and toll-like receptors that are upregulated in CD. Fifth, epidemiological evidence, such as the timing of the inception of a CD "epidemic" in Sweden, the increased prevalence of CD in Finland and the United States in recent decades, the unusually low prevalence of CD in Germany, and the differential in prevalence between Finnish Karelians and Russian Karelians, may all be explained by oral vitamin D exposure increasing CD risk. The same is true of some seemingly contradictory results in the literature on the effects of breastfeeding on CD risk. If future research validates this hypothesis, adjustments to oral vitamin D consumption among those who have genetic susceptibility may decrease the risk of CD in these individuals.

Vitamin D and Calcium Supplementation Accelerates Randall's Plaque Formation in a Murine Model

Most kidney stones are made of calcium oxalate crystals. Randall's plaque, an apatite deposit at the tip of the renal papilla, is considered to at the origin of these stones. Hypercalciuria may promote Randall's plaque formation and growth. We analyzed whether long-term exposure of Abcc6^-/- mice (a murine model of Randall's plaque) to vitamin D supplementation, with or without a calcium-rich diet, would accelerate the formation of Randall's plaque. Eight groups of mice (including Abcc6^-/- and wild type) received vitamin D alone (100,000 UI/kg every 2 weeks), a calcium-enriched diet alone (calcium gluconate 2 g/L in drinking water), both vitamin D supplementation and a calcium-rich diet, or a standard diet (controls) for 6 months. Kidney calcifications were assessed by 3-dimensional microcomputed tomography, μ-Fourier transform infrared spectroscopy, field emission-scanning electron microscopy, transmission electron microscopy, and Yasue staining. At 6 months, Abcc6^-/- mice exposed to vitamin D and calcium supplementation developed massive Randall's plaque when compared with control Abcc6^-/- mice (P < 0.01). Wild-type animals did not develop significant calcifications when exposed to vitamin D. Combined administration of vitamin D and calcium significantly accelerates Randall's plaque formation in a murine model. This original model raises concerns about the cumulative risk of vitamin D supplementation and calcium intakes in Randall's plaque formation.

Adverse events from large dose vitamin D supplementation taken for one year or longer

In recent years, clinical trials increasingly have given large doses of vitamin D supplements to investigate possible health benefits beyond bone at high 25-hydroxyvitamin D levels. However, there are few publications on the safety of high-dose vitamin D given long term. The study objective was to investigate the cumulative relative risk (RR) of total adverse events, kidney stones, hypercalcemia and hypercalciuria from ≥2800 IU/d vitamin D₂ or D₃ supplementation, followed for one year or more in randomized controlled trials (RCTs). A systematic review was conducted in Medline Ovid, EMBASE and Cochrane in March 2018 to update results of studies published since a previous review in October 2015. RCTs were included if they gave vitamin D₂ or D₃ at ≥2800 IU/d for at least one year and reported on total adverse events or at least one calcium-related adverse event. There were a total of 32 studies that met the inclusion criteria. Of these, only 15 studies (3150 participants) reported one or more event of the outcomes of interest. Long-term high-dose vitamin D supplementation did not increase total adverse events compared to placebo in 1731 participants from 10 studies (RR = 1.05; 95% CI = 0.88, 1.24; p = 0.61), nor kidney stones in 1336 participants from 5 studies (RR = 1.26; 95% CI = 0.35, 4.58; p = 0.72). However, there was a trend for vitamin D to increase risk of hypercalcemia in 2598 participants from 10 studies (RR = 1.93; 95% CI = 1.00, 3.73; p = 0.05); while its effect on hypercalciuria in only 276 participants from 3 studies was inconclusive (RR = 1.93; 95% CI = 0.83, 4.46; p = 0.12). In conclusion, one year or longer supplementation with a large daily, weekly or monthly dose of vitamin D₂ /D₃ did not significantly increase a risk of total adverse events or kidney stones, although there was a trend towards increased hypercalcemia, and possibly for hypercalciuria.

Meeting report of the "Symposium on kidney stones and mineral metabolism: calcium kidney stones in 2017"

A symposium on kidney stones and mineral metabolism held on December 2017 in Brussels, Belgium was the first international multidisciplinary conference of the International Collaborative Network on Kidney Stones and Mineral Metabolism. This meeting addressed epidemiology, underlying pathophysiological mechanisms, genetics, pathological, as well as clinical and research topics. The participants included clinicians and recognized experts in the field from Europe and the United States interacted closely during the symposium which promoted a chance to explore new frontiers in the field of kidney stone disease. This manuscript summarizes some of the major highlights of the meeting.

Phosphaturia in kidney stone formers: Still an enigma

Calcium kidney stones are common worldwide. Most are idiopathic and composed of calcium oxalate. Calcium phosphate is present in around 80% and may initiate stone formation. Stone production is multifactorial with a polygenic genetic contribution. Phosphaturia is found frequently among stone formers but until recently received scant attention. This review examines possible mechanisms for the phosphaturia and its relevance to stone formation from a wide angle. There is a striking lack of clinical data. Phosphaturia is associated, but not correlated, with hypercalciuria, increased 1,25 dihydroxy-vitamin D [1,25 (OH)₂D], and sometimes evidence of disturbances in proximal renal tubular function. Phosphate reabsorption in the proximal renal tubules requires tightly regulated interaction of many proteins. Paracellular flow through intercellular tight junctions is the major route of phosphate absorption from the intestine and can be reduced therapeutically in hyperphosphatemic patients. In monogenic defects stones develop when phosphaturia is associated with hypercalciuria, generally explained by increased 1,25 (OH)₂D production in response to hypophosphatemia. Calcification does not occur in disorders with increased FGF23 when phosphaturia occurs in isolation and 1,25 (OH)₂D is suppressed. Candidate gene studies have identified mutations in the phosphate transporters, but in few individuals. One genome-wide study identified a polymorphism of the phosphate transporter gene SLC34A4 associated with stones. Others did not find mutations obviously linked to phosphate reabsorption. Future genetic studies should have a wide trawl and should focus initially on groups of patients with clearly defined phenotypes. The global data should be pooled.

High Doses of Boron Have No Protective Effect Against Nephrolithiasis or Oxidative Stress in a Rat Model

Boron plays roles in the metabolism of calcium, vitamin D, steroid hormones, healthy bone development, and maintenance of cell membranes. The biological effects of boron are dose-dependent but follow a U-shaped pattern, rendering it important to define the active range. The studies of Bahadoran et al. on rats and Naghii et al. on humans showed that low doses of boron (3 and 10 mg/day) prevented kidney stone formation. The aim of this study was to determine whether high doses of boron have an anti-urolithiatic or antioxidant effect on nephrolithiasis in an experimental rat model. The study was conducted on 50 adult male Wistar rats randomized to five groups. Nephrolithiasis was induced with water containing 0.75% ethylene glycol (EG) and 2% ammonium chloride (AC). This treatment was given to animals in all groups for 10 days, except the positive and negative controls. Simultaneously, groups 2, 3, and 4 were given boric acid via gavage at doses of 25, 50, and 100 mg/kg/day (equivalent to 4/8/16 mg boron respectively) as the source of boron. Animals in the negative and positive control groups were given 6 μL/g distilled water without boric acid. At day 10, intra-cardiac blood samples were drawn from all animals. The right and left kidneys were removed for biochemical and histopathological examinations, respectively. The groups were compared with respect to serum urea, creatinine, calcium, phosphorous, total antioxidant status (TAS), total oxidant status (TOS), serum paraoxonase (PON1) activity, tissue calcium and oxalate levels, and stone burden as determined by histopathological examination. Serum urea and creatinine levels were significantly higher (p < 0.001 and p < 0.05, respectively), while serum calcium and phosphorous levels were significantly lower (p < 0.001 and p < 0.001, respectively), in animals given EG/AC compared to negative controls. No significant differences were detected in serum calcium, phosphorous, urea, or creatinine levels between animals treated with boron and positive controls (p > 0.05). Serum PON1 activity was significantly lower in animals given EG/AC than in negative controls (p < 0.001), while no significant difference in serum PON1 level was detected between rats treated with boron and positive controls. No significant differences were detected in vitamin D, TAS, TOS, tissue calcium, or tissue oxalate levels among groups. No stone formation was detected on histopathological examination in negative controls. No significant differences were found in stone formation between rats treated with boron and positive controls. Based on this study, high doses of boron had no protective effect against nephrolithiasis and oxidative stress.

Vitamin D, Hypercalciuria and Kidney Stones

The estimated lifetime risk of nephrolithiasis is growing nowadays, and the formation of kidney stones is frequently promoted by hypercalciuria. Vitamin D, and especially its active metabolite calcitriol, increase digestive calcium absorption—as urinary calcium excretion is directly correlated with digestive calcium absorption, vitamin D metabolites could theoretically increase calciuria and promote urinary stone formation. Nevertheless, there was, until recently, low evidence that 25-hydroxyvitamin D serum levels would be correlated with kidney stone formation, even if high calcitriol concentrations are frequently observed in hypercalciuric stone formers. Low 25-hydroxyvitamin D serum levels have been associated with a broad spectrum of diseases, leading to a huge increase in vitamin D prescription in the general population. In parallel, an increased frequency of kidney stone episodes has been observed in prospective studies evaluating vitamin D alone or in association with calcium supplements, and epidemiological studies have identified an association between high 25-hydroxyvitamin D serum levels and kidney stone formation in some groups of patients. Moreover, urinary calcium excretion has been shown to increase in response to vitamin D supplements, at least in some groups of kidney stone formers. It seems likely that predisposed individuals may develop hypercalciuria and kidney stones in response to vitamin D supplements.

Drug-Induced Kidney Stones and Crystalline Nephropathy: Pathophysiology, Prevention and Treatment

Drug-induced calculi represent 1-2% of all renal calculi. The drugs reported to produce calculi may be divided into two groups. The first one includes poorly soluble drugs with high urine excretion that favour crystallisation in the urine. Among them, drugs used for the treatment of patients with human immunodeficiency, namely atazanavir and other protease inhibitors, and sulphadiazine used for the treatment of cerebral toxoplasmosis, are the most frequent causes. Besides these drugs, about 20 other molecules may induce nephrolithiasis, such as ceftriaxone or ephedrine-containing preparations in subjects receiving high doses or long-term treatment. Calculi analysis by physical methods including infrared spectroscopy or X-ray diffraction is needed to demonstrate the presence of the drug or its metabolites within the calculi. Some drugs may also provoke heavy intra-tubular crystal precipitation causing acute renal failure. Here, the identification of crystalluria or crystals within the kidney tissue in the case of renal biopsy is of major diagnostic value. The second group includes drugs that provoke the formation of urinary calculi as a consequence of their metabolic effects on urinary pH and/or the excretion of calcium, phosphate, oxalate, citrate, uric acid or other purines. Among such metabolically induced calculi are those formed in patients taking uncontrolled calcium/vitamin D supplements, or being treated with carbonic anhydrase inhibitors such as acetazolamide or topiramate. Here, diagnosis relies on a careful clinical inquiry to differentiate between common calculi and metabolically induced calculi, of which the incidence is probably underestimated. Specific patient-dependent risk factors also exist in relation to urine pH, volume of diuresis and other factors, thus providing a basis for preventive or curative measures against stone formation.