Relation between hypercalciuria and vitamin D3-status in patients with urolithiasis

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.

Beta-thalassaemia major: Prevalence, risk factors and clinical consequences of hypercalciuria

Regular transfusion and chelation therapy produces increased life expectancy in thalassaemic patients who may develop new complications. Since few data are available regarding hypercalciuria in β‐thalassaemia major (TM), the aim of our study was to evaluate its prevalence, risk factors and clinical consequences. We enrolled 176 adult TM patients followed at the Center of Thalassemia of Ferrara. Hypercalciuria was defined by a calciuria of 4 mg/kg/day or more in a 24‐h urine sample. Anamnestic, biochemical and radiological data were collected. Hypercalciuria prevalence was reported in 69.3% of patients (females 52.5%). Hypercalciuric (HC) patients used deferasirox (DFX) more often than normocalciuric (NC) patients (47.5% vs 29.6%; p < 0.05). In HC subjects plasma parathyroid hormone (PTH) (24.1 ± 10.4 vs 30.1 ± 13.2 pg/ml) and phosphate levels (3.6 ± 0.5 vs 3.8 ± 0.7 mg/dl) were lower, whereas serum calcium (9.6 ± 0.4 vs 9.4 ± 0.4 mg/dl) and urinary 24‐h phosphaturia (0.9 ± 0.4 vs 0.6 ± 0.3 g/day) were higher as compared to NC patients (p < 0.05 for all comparisons). Supplementation with oral calcium and cholecalciferol was similar between the groups. A higher rate of kidney stones was present in HC (14.8%) versus NC patients (3.7%) (p < 0.05). Hypercalciuria is a frequent complication in adequately treated adult TM patients. Hypercalciuria prevalence is increased in DFX users whereas haemoglobin level or calcium supplements play no role. A significant proportion of HC patients developed kidney stones.

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.

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.

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.

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

Many studies compared the serum/plasma 1,25 dihydroxyvitamin D₃ (1,25(OH)₂D) and 25 hydroxyvitamin D₃ (25(OH)D) between people with and without nephrolithiasis, and their results were conflicting. After systematically searching PubMed, Web of Science, The Cochrane Library, CNKI, and the Wanfang Database, we conducted a meta-analysis. Thirty-two observational studies involving 23,228 participants were included. Meta-analysis of these studies showed that of stone formers (SFs), calcium SFs had significantly higher concentrations of 1,25(OH)₂D (weighted mean difference (WMD), 10.19 pg/mL; 95% confidence interval (CI), 4.31-16.07; p = 0.0007 and WMD, 11.28 pg/mL; 95% CI, 4.07-18.50; p = 0.002, respectively) than non-stone formers, while the levels of 25(OH)D (WMD, 0.88 ng/mL; 95% CI, -1.04-2.80; p = 0.37 and WMD, -0.63 ng/mL; 95% CI, -2.72-1.47; p = 0.56, respectively) are similar. Compared with controls and normocalciuria SFs, hypercalciuria SFs had increased circulating 1,25(OH)₂D (WMD, 9.41 pg/mL; 95% CI, 0.15-18.67; p = 0.05 and WMD, 2.75 pg/mL; 95% CI, -0.20-5.69; p = 0.07, respectively) and markedly higher 25(OH)D (WMD, 5.02 ng/mL; 95% CI, 0.99-9.06; p = 0.01 and WMD, 5.02 ng/mL; 95% CI, 2.14-7.90; p = 0.0006, respectively). Normocalciuria SFs had elevated 1,25(OH)₂D level (WMD, 6.85 pg/mL; 95% CI, -5.00-18.71; p = 0.26) and comparable 25(OH)D (WMD, 0.94 ng/mL; 95% CI, -3.55-5.43; p = 0.68). Sensitivity analysis generated similar results. Current evidence suggests that increased circulating 1,25(OH)₂D is associated with urinary stones and a higher level of circulating 25(OH)D is significantly associated with hypercalciuria urolithiasis. Further studies are still needed to reconfirm and clarify the role of vitamin D in the pathogenesis of stones.

Association between serum vitamin D levels and the risk of kidney stone: evidence from a meta-analysis

Background

Many epidemiological studies have conducted to evaluate the association between serum vitamin D levels and the risk of kidney stone. The aim of this study was to summarize the evidence from epidemiological studies between them.

Methods

Pertinent studies were identified by a search of PubMed, Embase, the Cochrane Library, China National Knowledge Infrastructure (CNKI) and China Biology Medical literature up to July 2015. Standardized mean difference (SMD) was conducted to combine the results. Random-effect model was used. Publication bias was estimated using Egger’s regression asymmetry test.

Results

Seven articles involving 451 kidney stone cases and 482 controls were included in this meta-analysis. Our pooled results suggested that kidney stone patients had a significantly higher serum vitamin D level compared with controls [summary SMD = 0.65, 95 % CI = 0.51, 0.79, I² = 97.0 %]. The associations were also significant both in Europe [SMD = 0.35, 95 % CI = 0.17, 0.53] and in Asia [SMD = 1.00, 95 % CI = 0.76, 1.25]. No publication bias was found.

Conclusions

Our analysis indicated that serum vitamin D level in kidney stone patients was significantly higher than that in non-kidney stone controls, both in Europe and Asia populations.

Electronic supplementary material

The online version of this article (doi:10.1186/s12937-016-0148-y) contains supplementary material, which is available to authorized users.

Combined vitamin D and calcium supplementation in vitamin D inadequate patients with urolithiasis: Impact on hypercalciuria and de novo stone formation

INTRODUCTION

We examined the effect of combined vitamin D and calcium supplementation (VDCS) on urinary calcium excretion and de novo stone formation in vitamin D inadequate (VDI) urolithiasis patients.

METHODS

We retrospectively reviewed the data of VDI patients (serum 25-hydroxyvitamin D <75 nmol/L) followed at a tertiary stone centre between September 2009 and December 2014. VDI patients with history of urolithiasis, who were placed on VDCS for abnormal bone mineral density or hyperoxaluria, were included. Hypercalciuric patients and patients on thiazide diuretics were excluded. Metabolic stone workup and two 24-hour urine collections were performed before and after VDCS.

RESULTS

In total, we included 34 patients, with a mean age of 54.8 years and a mean body mass index of 25.7 kg/m(2). After VDCS, there was a significant increase in the mean serum 25-hydroxyvitamin D (52.0 vs. 66.4 nmol/L, p < 0.001) and the mean urinary calcium excretion (3.80 vs. 5.64 mmol/d, p < 0.001). Eight (23.5%) patients developed de novo hypercalciuria. After a median follow-up of 39 (range: 7-60) months, 50% of hypercalciuric patients developed stones compared with 11.5% of non-hypercalciuric patients (p = 0.038).

CONCLUSION

This study showed a significant effect of combined VDCS on mean urinary calcium excretion, de novo hypercalciuria, and stone development in VDI patients with history of urolithiasis. Therefore, VDI urolithiasis patients receiving VDCS are advised to have monitoring with 24-hour urine collections and imaging studies. Although small, our sample size was good enough to validate the statistical outcomes. Prospective studies are needed to confirm these results.

Association of urinary calcium excretion with serum calcium and vitamin D levels

BACKGROUND AND OBJECTIVES

Population-based data on urinary calcium excretion are scarce. The association of serum calcium and circulating levels of vitamin D [25(OH)D2 or D3] with urinary calcium excretion in men and women from a population-based study was explored.

DESIGN, SETTINGS, PARTICIPANTS, & MEASUREMENTS

Multivariable linear regression was used to explore factors associated with square root-transformed 24-hour urinary calcium excretion (milligrams per 24 hours) taken as the dependent variable with a focus on month-specific vitamin D tertiles and serum calcium in the Swiss Survey on Salt Study.

RESULTS

In total, 624 men and 669 women were studied with mean ages of 49.2 and 47.0 years, respectively (age range=15-95 years). Mean urinary calcium excretion was higher in men than in women (183.05 versus 144.60 mg/24 h; P<0.001). In adjusted models, the association (95% confidence interval) of square root urinary calcium excretion with protein-corrected serum calcium was 1.78 (95% confidence interval, 1.21 to 2.34) mg/24 h per milligram per deciliter in women and 0.59 (95% confidence interval, -0.11 to 1.29) mg/24 h per milligram per deciliter in men. Men in the third 25(OH)D3 tertile had higher square root urinary calcium excretion than men in the first tertile (0.99; 95% confidence interval, 0.36 to 1.63 mg/24 h per nanogram per milliliter), and the corresponding association was 0.32 (95% confidence interval, -0.22 to 0.85) mg/24 h per nanogram per milliliter in women. These sex differences were more marked under conditions of high urinary sodium or urea excretions.

CONCLUSIONS

There was a positive association of serum calcium with urinary calcium excretion in women but not men. Vitamin 25(OH)D3 was associated with urinary calcium excretion in men but not women. These results suggest important sex differences in the hormonal and dietary control of urinary calcium excretion.

Role of 1,25-dihydroxy vitamin D3 and parathyroid hormone in urinary calcium excretion in calcium stone formers

PURPOSE

To find out the possible role of 1,25(OH)₂ vitamin D₃ [1,25(OH)₂D₃] and parathyroid hormone (PTH) as intrinsic factors in urinary calcium stone formers (SFs), we investigated their relationship with serum and urinary biochemical parameters.

MATERIALS AND METHODS

A total of 326 calcium SFs (male: 204, female: 122) were enrolled and underwent outpatient metabolic evaluations including 1,25(OH)₂D₃ and PTH as well as serum and 24-hour urinary biochemical parameters. As control, 163 age- and sex-matched (2:1) individuals (non-SFs) who have never urinary stone episode were included.

RESULTS

1,25(OH)₂D₃ level was positively correlated with urinary calcium excretion (r=0.347, p<0.001). The hypercalciuric group and recurrent SFs had higher serum 1,25(OH)₂D₃ levels than the normocalciuric group (p<0.001) and first SFs (p=0.050). In the adjusted multiple linear regression analysis, serum 1,25(OH)₂D₃ level (β=0.259, p<0.001) and serum PTH level (β=-0.160, p<0.001) were significantly correlated with urinary calcium excretion. The patients in highest tertile of 1,25(OH)₂D₃ had a more than 3.1 fold risk of hypercalciuria than those in the lowest tertile (odds ratio=3.14, 95% confidence interval: 1.431-6.888, p=0.004). No correlation was observed between PTH and 1,25(OH)₂D₃ (R=0.005, p=0.929) in calcium SFs, while a negative correlation was found in controls (R=-0.269, p=0.001).

CONCLUSION

1,25(OH)₂D₃ was closely correlated with urinary calcium excretion, and high 1,25(OH)₂D₃ levels were detected in the hypercalciuric group and in recurrent SFs. However, 1,25(OH)₂D₃ was not correlated with PTH in calcium SFs. These findings suggest that 1,25(OH)₂D₃ might be important intrinsic factor for altered calcium regulation in SFs.

Effects of high doses of cholecalciferol in normal subjects: a randomized double-blinded, placebo-controlled trial

BACKGROUND

Vitamin D repletion with high doses of vitamin D is often recommended to patients and healthy subjects. The safety, especially concerning changes in urinary calcium excretion is of great importance.

METHODS

In a double-blinded, placebo-controlled study in 40 healthy volunteers, we examined the changes in mineral metabolism during supplementation with 3000 IU of oral cholecalciferol daily during 4 months.

RESULTS

Both 25(OH)vitamin D and 1,25(OH)2vitamin D increased significantly in the active treated group as compared to the placebo group (186% versus 14% (P<0.001) and 28% versus -8% (P<0.001)). No change was observed in urinary calcium excretion in the active group compared to the placebo group (P = 0.891). Fibroblast growth factor 23 increased significantly by 10% (P<0.018) in the active group. However, there was no difference in changes in FGF23 between treatment groups (P = 0.457).

CONCLUSION

High dose cholecalciferol significantly increases 25(OH)vitamin D and 1,25(OH)2vitamin D levels compared to placebo. No changes in urinary calcium excretion or other measured components of the mineral metabolism were found between groups.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00952562.

Effect of calcium intake on serum levels of 25-hydroxyvitamin D3

The effects of high calcium intake on vitamin D metabolism were investigated. To the normal diet of 14 healthy men, 2 g calcium were added daily for 6-7 weeks. The mean serum concentration of 25-hydroxyvitamin D3 increased from 73 +/- 7 to 94 +/- 6 nmol l-1 (P less than 0.05, Student's unpaired t-test; P less than 0.01, paired t-test) in the subjects receiving calcium, whereas there was only a minimal increase, from 67 +/- 5 to 71 +/- 4 nmol l-1 in a control group on a normal diet. At the end of the study the difference between the test group and the controls was highly significant (P less than 0.005). The calcium loading caused a statistically significant depression of the serum levels of 1,25-dihydroxyvitamin D. The results obtained are in agreement with previous studies in rats and indicate that calcium intake is of some importance for the serum level of 25-hydroxyvitamin D3. The findings are discussed in relation to our previous finding that there is a relationship between high 25-hydroxyvitamin D3 levels and hypercalciuria in renal-stone formers.

Proposed criteria for identifying hyperabsorbers among normocalcaemic renal stone formers

Normocalcaemic male stone formers (n = 138), 31-51 years of age, were divided into a hypercalciuric group (n = 80), with calcium excretions exceeding 7.0 mmol/24 h, and a normocalciuric group (n = 58), with calcium excretions of 7.0 mmol/24 h or less. The hypercalciuric group of patients was further subdivided using two previously published methods for identifying hyperabsorbers--one based on fasting urinary calcium/creatinine ratios and renal threshold phosphate concentrations, Jongen and the other method based on an oral calcium load test, Pak et al. The first method identified 37 patients and the second method 12 patients as hyperabsorbers. However, of the latter 12 patients only 8 were identified as hyperabsorbers using the first method of classification. It is thus evident that the two methods used for subclassification may give surprisingly different results. In order to obtain better congruence, the consequences of changing the defining limits in the two different methods were investigated. On the basis of the results obtained a new model for identification of hyperabsorbers is presented and discussed. With these new selection criteria (TmPO4/GFR greater than or equal to 0.75, urinary fasting molar calcium/creatinine ratio less than 0.40, and an increase in urinary molar calcium/creatinine ratio after calcium load greater than or equal to 0.20), 27 of the hypercalciuric patients were identified as hyperabsorbers. This group included 23 of Jongen's 37 and all of Pak's 12 hyperabsorbers. No patient not identified as a hyperabsorber according to either Jongen's or Pak's method were found in this group. The suggested model for identifying hyperabsorbers seems to be practical at least in studies on the relation between hypercalciuria and metabolism of vitamin D3.

Studies on the relationship between vitamin D3 status and urinary excretion of calcium in healthy subjects: effects of increased levels of 25-hydroxyvitamin D3

The metabolic consequences of a rapid increase in vitamin D status in healthy subjects were investigated. Circulating levels of 25-hydroxyvitamin D3 were increased by 224% in 12 healthy men by giving oral vitamin D3 for 7 weeks and by 200% in 15 healthy women by UVB irradiation for 7 weeks. No statistically significant effects on the serum levels of calcium, phosphate, creatinine, urate, albumin, PTH, basal urinary excretion of calcium, fasting urinary excretion of cAMP, or urinary excretion of calcium after calcium load tests were observed with the unpaired t-test. With the paired t-test the small stimulatory effects (about 25%) on basal urinary excretion of calcium became statistically significant in both experiments. The ratio between calcium and creatinine in fasting urine was significantly elevated following UVB irradiation (from 0.11 +/- 0.02 to 0.21 +/- 0.04, p less than 0.025 unpaired t-test, p less than 0.02 paired t-test) but not after oral intake of vitamin D3. The level of 1,25-dihydroxyvitamin D in serum was not affected to a statistically significant degree by oral vitamin D3, whereas there was a slight decrease from 48 +/- 3 to 39 +/- 3 pmol/l following UVB irradiation. It is concluded that an increase in the concentration of 25-hydroxyvitamin D3 up to about 125 nmol/l has small and negligible effects on calcium homeostasis in healthy subjects. This finding is discussed in relation to our previous finding that hypercalciuric renal stone formers have elevated serum levels of 25-hydroxyvitamin D3 as compared with normocalciuric stone formers and healthy subjects.

High circulating levels of 25-hydroxyvitamin D3 in renal stone formers with hyperabsorptive hypercalciuria

Normocalcaemic male stone formers, 31-51 years old (n = 108) on a free diet, were divided into a hypercalciuric group (n = 47) with calcium excretion rates higher than 8.0 mmol/24 h, a normocalciuric group (n = 32) with calcium excretion rates below 6.1 mmol/24 h and an intermediate group (n = 29). There were no statistically significant differences between the hypercalciuric and the normocalciuric groups with respect to serum levels of calcium, phosphate, creatinine, urate, ALAT, albumin, PTH, 1,25-dihydroxyvitamin D or urinary excretion of cAMP. The group of patients with high calcium excretion had significantly higher serum levels of 25-hydroxyvitamin D3 (75 +/- 4 nmol/l) than the group with low calcium excretion (57 +/- 4 nmol/l) (p less than 0.002), while the group of patients with intermediate calcium excretion had 25-hydroxyvitamin D3 levels between the other two groups (69 +/- 4 nmol/l). A highly accurate method based on isotope dilution-mass spectrometry was used to assay 25-hydroxyvitamin D3. Of the patients with hypercalciuria (n = 47), seven were classified as hyperabsorbers on the basis of calcium load tests. These patients were found to have even higher serum levels of 25-hydroxyvitamin D3 (108 +/- 10 nmol/l)--significantly higher than that of the hypercalciuric patients as a whole. The above study was carried out in March 1983. In September, the group of patients with high urinary calcium excretion also had significantly higher levels of 25-hydroxyvitamin D3 than the group of patients with low calcium excretion.(ABSTRACT TRUNCATED AT 250 WORDS)

Cellulose phosphate and chlorothiazide in childhood idiopathic hypercalciuria

A calcium loading test performed on seven of eight children with idiopathic hypercalciuria identified the hyperabsorptive form of hypercalciuria in five and renal hypercalciuria in one. The type of hypercalciuria was not identified in the other patient. Three children presented with hematuria without calculus formation. Chlorothiazide reduced the urinary calcium excretion level in two of six patients to the normal range. The addition of cellulose phosphate to chlorothiazide reduced the urinary calcium excretion level to the normal range in those four patients who showed an incomplete response to chlorothiazide alone. There was clinical improvement with cellulose phosphate in another child whose symptoms did not disappear after chlorothiazide had reduced urinary calcium level to the normal range. Cellulose phosphate is effective in children with recurrent stone formation who have shown inadequate response to chlorothiazide.