Variables related to urinary calcium excretion in young girls

Calcium Intake in Bone Health: A Focus on Calcium-Rich Mineral Waters

Calcium is an essential element that plays numerous biological functions in the human body, of which one of the most important is skeleton mineralization. Bone is a mineralized connective tissue in which calcium represents the major component, conferring bone strength and structure. Proper dietary calcium intake is important for bone development and metabolism, and its requirement can vary throughout life. The mineral composition of drinking water is becoming relevant in the modulation of calcium homeostasis. In fact, calcium present in mineral drinking waters is an important quantitative source of calcium intake. This, together with its excellent bioavailability, contributes to the maintenance of the bone health. This article aims to examine studies that assessed the bioavailability of the calcium contained in calcium-rich mineral waters and their impact on bone health, including original data collected in a recent study in humans.

Using stable isotope tracers to study bone metabolism in children

Skeletal mineralization is initiated in utero and continues throughout childhood and adolescence. During these key periods of the life cycle, calcium retention must increase significantly to provide sufficient mineral for bone deposition and skeletal growth. Stable calcium isotopes have served as a fundamental tool to non-invasively characterize the dynamic changes in calcium physiology that occur from infancy through adolescence. These approaches have helped define the dynamics of calcium absorption and utilization in healthy children and in children with chronic diseases. As data in this area have accumulated, new areas of emphasis are beginning to characterize the determinants of variability in mineral retention, the genetic determinants of bone turnover and calcium flux and the impact of the gut microbiome on whole body and niche specific calcium dynamics. Advances in these areas will help define calcium utilization in paediatric populations and provide information that may be useful in maximizing bone acquisition across this critical phase of the life cycle.

Evidence of disordered calcium metabolism in adolescent girls with type 1 diabetes: An observational study using a dual-stable calcium isotope technique

Type 1 diabetes (T1D) is associated with skeletal abnormalities including low bone density and increased fracture risk. The pathophysiology underlying T1D related skeletal fragility remains unknown. The objective of this study was to use a dual-stable calcium isotope method to investigate the effects of T1D on calcium absorption and estimated calcium retention in adolescent females. Twenty adolescent females with T1D were admitted for a 24-h calcium absorption study using oral (⁴⁴Ca) and intravenous (⁴²Ca) stable isotopes for determination of percent gastrointestinal calcium absorption and estimated calcium retention. Five out of twenty participants were found to have negative estimated calcium retention. Participants with negative calcium retention had greater urinary calcium excretion [202mg/d (IQR: 178-213)] compared to those with positive calcium retention [101.5mg/d (IQR: 82-122)], p=0.01, but similar calcium intake and percent calcium absorption. With the exception of one outlier, 24-h urine calcium was significantly associated with hemoglobin A1c (Pearson's r=0.55, p=0.02). 50% of participants consumed less than the RDA for calcium; fractional calcium absorption was inversely correlated with calcium intake in participants not meeting the RDA (Spearman's rho -0.65, p=0.04). In conclusion, one-quarter of adolescent girls with T1D were found to have negative estimated calcium retention at a time when bone mineral accrual should be ongoing. This appeared to be the result of excess urinary calcium excretion as opposed to diminished gastrointestinal calcium absorption. Insufficient calcium availability for bone deposition during adolescence could impair bone mineral accrual and contribute to skeletal fragility. Trial registered: ClinicalTrials.gov Reg No. NCT03156179.

Evidence in favor of a severely impaired net intestinal calcium absorption in patients with (early-stage) chronic kidney disease

INTRODUCTION

Calcium and phosphorus are essential to many vital physiological processes. Little is known about the net and fractional intestinal absorption of calcium and phosphorus in patients with chronic kidney disease (CKD) and their clinical and hormonal determinants.

METHODS

Blood and 24-hour urine samples were collected in 20 healthy volunteers (HV) and 72 stable CKD stage 1-4 patients and analyzed for parameters of mineral metabolism including calcidiol, calcitriol, and parathyroid hormone (PTH). Dietary intake was assessed by dietary history.

RESULTS

The 24-hour urinary calcium excretion, as opposed to the phosphorus excretion, showed a stepwise decrease across CKD stages (median of 219, 84, 40, and 22 mg/day in HV and patients with CKD stages 1-2, 3 and 4, respectively). Younger age, high serum calcitriol, and high estimated GFR were associated with a high 24-hour urinary calcium excretion. High serum calcitriol levels and dietary phosphorus intake were associated with a high 24-hour urinary phosphorus excretion. The fractional intestinal calcium absorption, as estimated by the urinary-to-ingested calcium ratio, decreased across CKD stages.

CONCLUSIONS

The 24-hour urinary excretion of calcium, as opposed to phosphorus, is markedly decreased in CKD, even in early-stage disease. This is partly explained by low calcitriol levels and older age. Assuming a neutral calcium balance at the time of urine collection, we infer that net intestinal calcium absorption may be severely impaired in CKD.

Gender and age differences in mixed metal exposure and urinary excretion

BACKGROUND

Little is known about the variation in exposure to toxic metals by age and gender and other potential modifying factors. We evaluated age and gender differences by measurements of metal/element concentrations in urine in a rural population in Matlab, Bangladesh, in three age groups: 8-12 (N=238), 14-15 (N=107) and 30-88 (N=710) years of age, living in an area with no point sources of metal exposure but where elevated water arsenic concentrations are prevalent.

RESULTS

We found marked differences in urine concentrations of metals and trace elements by gender, age, tobacco use, socioeconomic and nutritional status. Besides a clearly elevated urinary arsenic concentration in all age groups (medians 63-85 μg As/L), and despite the low degree of contamination from industries and traffic, the urine concentrations of toxic metals such as cadmium and lead were clearly elevated, especially in children (median 0.31 μg Cd/L and 2.9 μg Pb/L, respectively). In general, women had higher urinary concentrations of toxic metals, especially Cd (median 0.81 μg/L) compared to men (0.66 μg/L) and U (median 10 ng/L in women, compared to 6.4 ng/L in men), while men had higher urinary concentrations of the basic and essential elements Ca (69 mg/L in men, 30-50 years, compared to 52 mg/L in women), Mg (58 mg/L in men compared to 50 mg/L in women), Zn (182 μg/L in men compared to 117 μg/L in women) and Se (9.9 μg/L in men compared to 8.7 μg/L in women). Manganese was consistently higher in females than in males in all age groups, suggesting a biological difference between females and males in Mn metabolism. Increasing socioeconomic status decreased the toxic metal exposure significantly in children and especially in men. Poor iron status was detected in 17% of children, adolescents and women, but only in 6% of men. Also zinc deficiency was more prevalent in females than in males.

CONCLUSIONS

Women and children seemed to be more at risk for toxic metal exposure than men and at the same time more vulnerable to micronutrient deficiency. Higher concentrations of the toxic metals in urine in women are likely to reflect an increased gastrointestinal absorption of these metals at micronutrient deficiency, such as low body iron stores and Zn deficiency. Higher urinary concentrations of the essential elements in men likely reflect a better nutritional status. There is a need for information on exposure, lifestyle and socioeconomic factors, stratified by gender and age, for the purpose of conducting balanced risk assessment and management that considers such differences.

Evaluation of the Children's Eating Habits Questionnaire used in the IDEFICS study by relating urinary calcium and potassium to milk consumption frequencies among European children

BACKGROUND

Measuring dietary intake in children is notoriously difficult. Therefore, it is crucial to evaluate the performance of dietary intake assessment methods in children. Given the important contribution of milk consumption to calcium (Ca) and potassium (K) intakes, urinary calcium (UCa) and potassium (UK) excretions in spot urine samples could be used for estimating correlations with milk consumption frequencies.

OBJECTIVE

The aim of this study was to evaluate the assessment of milk consumption frequencies derived from the Food Frequency Questionnaire section of the Children's Eating Habits Questionnaire (CEHQ-FFQ) used in the IDEFICS (Identification and prevention of dietary- and lifestyle induced health effects in children and infants) study by comparing with UCa and UK excretions in spot urine samples.

DESIGN

This study was conducted as a setting-based community-oriented intervention study and results from the first cross-sectional survey have been included in the analysis.

SUBJECTS

A total of 10,309 children aged 2-10 years from eight European countries are included in this analysis.

METHODS

UCa and UK excretions were measured in morning spot urine samples. Calcium and potassium urine concentrations were standardised for urinary creatinine (Cr) excretion. Ratios of UCa/Cr and UK/Cr were used for multivariate regression analyses after logarithmic transformation to obtain normal distributions of data. Milk consumption frequencies were obtained from the CEHQ-FFQ. Multivariate regression analyses were used to investigate the effect of milk consumption frequencies on UCa and UK concentrations, adjusting for age, gender, study centre, soft drink consumption and frequency of main meals consumed at home.

RESULTS

A significant positive correlation was found between milk consumption frequencies and ratios of UK/Cr and a weaker but still significant positive correlation with ratios of UCa/Cr, when using crude or partial Spearman's correlations. Multivariate regression analyses showed that milk consumption frequencies were predictive of UCa/Cr and UK/Cr ratios, when adjusted for age, gender, study centre, soft drink consumption and frequency of main meals consumed at home. Mean ratios of UK/Cr for increasing milk consumption frequency tertiles showed a progressive increase in UK/Cr. Children consuming at least two milk servings per day had significantly higher mean UCa/Cr and UK/Cr ratios than children who did not. Large differences in correlations between milk consumption frequencies and ratios of UCa/Cr and UK/Cr were found between the different study centres.

CONCLUSION

Higher milk consumption frequencies resulted in a progressive increase in UK/Cr and UCa/Cr ratios, reflecting the higher Ca and K intakes that coincide with increasing milk consumption, which constitutes a major K and Ca source in children's diet.

Estudo da excreção urinária de cálcio, potássio e sódio com o emprego de citrato de potássio na hipercalciúria idiopática na criança

OBJETIVO: Estudar as relações entre a excreção urinária de cálcio, sódio e potássio e a associação sódio/potássio urinários em crianças com hipercalciúria idiopática em dieta habitual, antes e depois da administração de citrato de potássio na dose de 1mEq/kg/dia. MÉTODOS: Foram estudadas prospectivamente 26 crianças: 19 (73%) meninos e sete (27%) meninas com idade entre dois e 13 anos, portadores de hipercalciúria idiopática recém-diagnosticada por dosagem de cálcio em urina de 24 horas >4mg/kg/dia. O citrato de potássio foi administrado na dose de 1mEq/kg/dia. Foram realizadas dosagens séricas e em urina de 24 horas de cálcio (Ca), potássio(K), sódio (Na) e creatinina (Cr), antes e 15 dias depois da administração diária do citrato de potássio. Para comparar os resultados de cálcio/creatinina (Ca/Cr), potássio/creatinina (K/Cr) e sódio/potássio (Na/K) urinários nos dois momentos, aplicou-se o teste não-paramétrico de Wilcoxon. Para a análise das associações entre Ca/Cr e K/Cr e entre Ca/Cr e Na/Cr foi utilizado o coeficiente de correlação de Pearson. Considerou-se significante p<0,05. RESULTADOS: Após o uso de citrato de potássio, ocorreu significativa redução da calciúria e da relação Na/K urinários, bem como elevação na caliúria. Não houve modificação da excreção urinária de sódio. CONCLUSÕES: Em dieta habitual, o citrato de potássio eleva a caliúria e diminui a calciúria em criança hipercalciúricas, sendo um eficaz recurso terapêutico.

Urinary calcium excretion in healthy Turkish children

The aim of this study was to establish the age related reference percentile values for urinary calcium excretion in healthy Turkish children, and to determine the frequency of hypercalciuria and also the factors affecting urinary calcium excretion. A cross-sectional study was performed in Aydin, in western Turkey during winter. Study population was constituted from seventeen districts of this region (sample size was calculated from a formula using the results of the last population census) by stratified and random sampling methods. Urinary calcium excretion was measured as the calcium/creatinine concentration ratio in the second non-fasting urine samples. A total of 2252 children (1132 male) with a mean age of 8.57 +/- 4.44 years (ranged from 15 days to 15 years) were studied. The mean of urinary calcium/creatinine concentration ratio was calculated as 0.092 +/- 0.123. The percentile values between 3rd and 97th for urinary calcium/creatinine concentration ratio according to age were calculated and shown as multiple line graphs. Hypercalciuria prevalence was found as 9.6% when the upper limit of urinary calcium/creatinine concentration ratio was accepted as 0.21. Urinary calcium/creatinine concentration ratio of the children from different districts, altitudes, and ethnic origins were statistically different. Poor negative correlations were found between urinary calcium/creatinine concentration ratio and age and weight. No differences in urinary calcium/creatinine concentration ratios were observed in terms of sexes, diet, physical activity, urolithiasis in the family, symptoms related to hypercalciuria, amount of calcium in drinking water, and urine strip analysis. In conclusion, reference values for urinary calcium/creatinine concentration ratios should be established for children in each country and also in each geographic region.

A 7-week reduction in salt intake does not contribute to markers of bone metabolism in young healthy subjects

BACKGROUND

Sodium intake increases urinary calcium excretion and may thus lead to negative calcium balance and bone loss.

OBJECTIVE

We hypothesised that reducing sodium intake would reduce urinary calcium excretion and have a beneficial influence in bone metabolism.

DESIGN

A total of 29 subjects, 14 males and 15 females, were divided into two study groups. One group (low-sodium group (LS)) reduced sodium intake for 7 weeks by substituting low-salt alternatives for the most important dietary sources of sodium. The other group, serving as a control group (C), was given the same food items in the form of normally salted alternatives. Fasting serum samples as well as 24-h urine samples were obtained in the beginning and at the end of the study. Urinary sodium, urinary calcium, urinary creatinine, serum calcium, serum phosphate, serum creatinine, serum parathyroid hormone (s-PTH), serum C-terminal telopeptides of Type-I collagen and serum bone alkaline phosphatase (s-B-ALP) were analysed.

RESULTS

The LS group showed a significant decline (P = 0.001) in urinary sodium/creatinine ratio without a significant effect on urinary calcium/creatinine ratio. In the LS group, s-PTH increased (P = 0.03). The C group showed an increase in s-PTH (P = 0.05) and in s-B-ALP, but no differences were observed between the study groups in the changes of serum markers of calcium and bone metabolism.

CONCLUSIONS

We have shown that reducing the sodium intake of young, healthy people with adequate calcium intake over a 7-week period does not affect the markers of bone metabolism.

CALCIUM AND BONE MINERAL METABOLISM IN CHILDREN WITH CHRONIC ILLNESSES

Increased longevity and improved medical management of children with chronic illnesses has led to a focus on the short- and long-term consequences of these conditions on bone health. Bone loss is influenced by diet, malabsorption, and disease-related imbalances in bone turnover. It may be exacerbated by common medications, especially corticosteroids. Assessment of bone mass and quality, calcium absorption, kinetically derived rates of bone turnover, and biochemical markers of bone turnover have increased our knowledge of the pathophysiology of bone loss in these children as well as provided insights into possible therapeutic interventions. Increased intake of calcium and vitamin D, while useful, is unlikely to prevent or resolve bone loss in many chronically ill children. Emphasis on combination of nutritional interventions with exercise and newer bone-sparing therapies may be necessary.

Calcium, Sodium and Potassium Urinary Excretion during the First Five Days of Life in Very Preterm Infants

BACKGROUND

Hypercalciuria has been associated with the risk of nephrocalcinosis and renal stones in both adults and children. Renal calcifications are frequently encountered in preterm infants because this particular population presents most of the risk factors of increased urinary calcium excretion. Urinary calcium excretion has been shown to correlate with sodium and potassium excretions in adult patients, but these correlations have not been demonstrated in the early neonatal period yet.

OBJECTIVE

To define the relationship between calcium urinary excretion and sodium or potassium excretions in the first 5 days of life in preterm babies.

METHODS

A prospective study was conducted in 16 preterm infants born before 32 weeks of gestation (body weight 1,373 +/- 310 g; gestational age 29.1 +/- 1.6 weeks). Fifteen consecutive 8-hour urine collections were performed for each infant from the 8th hour of life. A plasma sample was obtained at the end of each urine collection. Sodium, potassium, calcium and creatinine were measured in urine and blood samples as often as possible.

RESULTS

(1) Urine sodium excretion was 6.56 +/- 4.35 mmol/kg per day. (2) Urinary calcium excretion was 5.9 +/- 5.4 mg/kg per day and the urinary calcium/creatinine ratio was 0.48 +/- 0.39 mg/mg. (3) Urinary calcium and sodium excretion were positively correlated (r = 0.65, p = 0.0001), while an inverse correlation was found between calcium and potassium excretion (r = 0.31, p = 0.004).

CONCLUSION

The mean values of urinary calcium excretion and calcium/creatinine ratio observed in our population were higher than 4 mg/kg per day and 0.4 mg/mg, respectively, i.e. boundary values previously associated with an increased risk of nephrocalcinosis. We hypothesize that an increase in urinary sodium excretion in this population may facilitate calcium excretion.

Fruit and vegetable intakes are an independent predictor of bone size in early pubertal children

BACKGROUND

Adequate intakes of fruit and vegetables are recommended for optimum health in children.

OBJECTIVE

The objective of this study was to determine whether consuming fruit and vegetables >3 times per day is beneficial to bone mass in children.

DESIGN

Fifty-six white females (Tanner stage 2) recorded dietary intake on 3 independent days. The numbers of servings of fruit and vegetables were recorded for each day and tallied, and the subjects were divided into 2 consumption groups for analysis (low consumption: <3 servings/d, n = 22; high consumption: > or = 3 servings/d, n = 34). Bone area and the bone mineral content of the whole body and radius were assessed by using dual-energy X-ray absorptiometry. Radioimmunoassays measured serum parathyroid hormone and 25-hydroxyvitamin D. Twenty-four-hour urine samples were assessed for calcium, sodium, and creatinine.

RESULTS

After adjustment for age, body mass index, and physical activity, those children who reported consuming > or = 3 servings fruit and vegetables/d had more bone area of the whole body (6.0%; P = 0.03) and radius (8.3%; P = 0.03), lower urinary calcium excretion (2.6 +/- 0.2 compared with 1.8 +/- 0.3 mg/kg; P = 0.04), and lower parathyroid hormone (19.6 +/- 1.9 compared with 25.0 +/- 1.6 pg/mL; P = 0.01) than did those children who reported consuming <3 servings fruit and vegetables/d.

CONCLUSIONS

High fruit and vegetable intakes have beneficial effects on the bone area of the radius and whole body in early pubertal girls. The lower urinary calcium output associated with higher fruit and vegetable intakes may be a modulating factor.

Efficiency of calcium absorption is not compromised in clinically stable prepubertal and pubertal girls with cystic fibrosis

BACKGROUND

Reduced bone mass is common in both children and adults with cystic fibrosis (CF) and may be a consequence of inadequate calcium absorption. The effect of CF on intestinal calcium absorption and retention has not been described in children.

OBJECTIVE

Calcium absorption and urinary losses were characterized in clinically stable girls with CF consuming self-selected diets and following usual pancreatic enzyme regimens.

DESIGN

The percentage of calcium absorption was assessed in 23 girls (aged 7-18 y) with CF by using oral ((44)Ca) and intravenous ((42)Ca) stable isotopes. Girls were grouped according to Tanner stage of breast development. True calcium absorption (V(a)) was determined as the product of percentage calcium absorption and average 4-d daily calcium intake. Calcium balance was estimated by subtracting urinary calcium and estimated endogenous fecal losses from the measure of V(a). Analysis of variance was used to compare outcomes among pubertal groups, and regression analysis was used to describe the relations of percentage and total calcium absorption to calcium intake and of urinary calcium to sodium excretion.

RESULTS

Percentage calcium absorption was inversely related to calcium intake. Percentage absorption and V(a) were similar to values observed in healthy girls in other studies. Total calcium absorption and estimated calcium balance were significantly greater among girls in early puberty (Tanner stages 2-3) than in prepubertal or late-pubertal girls (P < 0.05). Urinary calcium was positively related to urinary sodium excretion (P = 0.02).

CONCLUSION

The efficiency of calcium absorption was not compromised in clinically stable girls with CF.

Bone mineral content in girls perinatally infected with HIV

BACKGROUND

Early diagnostic efforts and advances in multidrug therapy have considerably prolonged the survival time of children infected perinatally with HIV. Despite these advances, few studies have addressed calcium status and bone growth in HIV-infected children.

OBJECTIVE

Our objective was to examine the effect of HIV infection on calcium status and bone growth in children.

DESIGN

We measured calcitropic hormones, urinary calcium excretion, bone mineral content, and body composition in 19 young girls aged 9.2 +/- 2.6 y (range: 5.9-15.2 y) who were infected perinatally with HIV.

RESULTS

Serum concentrations of 1,25-dihydroxyvitamin D [1,25(OH)(2)D] and parathyroid hormone concentrations were elevated above normal ranges in 25% and 12% of these girls, respectively. Urinary calcium excretion normalized for creatinine excretion was also elevated (Ca/Cr >0.18) in 17% of these children despite suboptimal calcium intakes (679 +/- 437 mg/d). Total-body bone mineral content, measured with the use of dual-energy X-ray absorptiometry, averaged 845.1 +/- 279.0 g and was on average 2.7 z scores below age- and race-matched values reported in non-HIV-infected healthy girls. Significant positive correlations were found between an indirect marker of bone resorption in urine (N:-telopeptide) and 1,25(OH)2D (P < 0.02, r2 = 0.586, n = 9), and between serum N-telopeptide and total alkaline phosphatase (P < 0.001, r2 = 0.541, n = 17), suggesting that calcium insufficiency may be increasing bone resorption in this group.

CONCLUSIONS

Young girls with HIV infection had low bone mass and evidence of calcium insufficiency. Nutritional counseling of children with HIV infection should emphasize adequate calcium intakes because of the importance of this age period in bone mineral acquisition.

Oligofructose stimulates calcium absorption in adolescents

BACKGROUND

In rats, nondigestible oligosaccharides stimulate calcium absorption. Recently, this effect was also found in human subjects.

OBJECTIVE

The objective of the study was to investigate whether consumption of 15 g oligofructose/d stimulates calcium absorption in male adolescents.

DESIGN

Twelve healthy, male adolescents aged 14-16 y received, for 9 d, 15 g oligofructose or sucrose (control treatment) daily over 3 main meals. The treatments were given according to a randomized, double-blind, crossover design, separated by a 19-d washout period. On the 8th day of each treatment period, 44Ca was given orally with a standard breakfast containing approximately 200 mg Ca. Within half an hour after administration of 44Ca, 48Ca was administered intravenously. Fractional calcium absorption was computed from the enrichment of 44Ca:43Ca and 48Ca:43Ca in 36-h urine samples, which was measured by inductively coupled plasma mass spectrometry.

RESULTS

An increase in true fractional calcium absorption (%) was found after consumption of oligofructose (mean difference +/- SE of difference: 10.8+/-5.6; P < 0.05, one sided). The results are discussed in relation to the methods used.

CONCLUSION

Fifteen grams of oligofructose per day stimulates fractional calcium absorption in male adolescents.

Think of genetic hypercalciuria when a child has urinary tract findings

Genetic hypercalciuria, one of the most common mineral disorders in childhood, is frequently associated with a variety of urinary tract problems. Identifying and treating genetic hypercalciuria alleviates urinary tract problems and optimizes peak bone mass growth in affected children. Advanced practice pediatric nurses play a key role in identifying and coordinating care for children with genetic hypercalciuria.

The relationship between urinary calcium, sodium, and potassium excretion and the role of potassium in treating idiopathic hypercalciuria

OBJECTIVES

1) To evaluate the relationships between urinary sodium (UNa), potassium (UK), and calcium (UCa) excretion in the pediatric population; and 2) to determine the effect of increasing potassium intake in patients with idiopathic hypercalciuria and investigate whether this intervention can be offered as another mode of therapy in this patient population.

DESIGN

Prospectively, we determined UNa, UK, UCa, and creatinine (Cr) concentrations in randomly collected urine samples from children on initial evaluation for urinary frequency, dysuria, hematuria, enuresis, or kidney stones to identify children with hypercalciuria.

SETTING

The outpatient renal clinic of an academic hospital.

PARTICIPANTS

Twenty-three black children (13 girls and 10 boys) and 77 white children (44 girls and 33 boys) 3.92 to 16.67 years of age.

INTERVENTIONS

Eleven children with hypercalciuria were given potassium supplementation or placed on a high-potassium diet for at least 2 weeks.

OUTCOME MEASURES

UNa to UK, UNa to Cr, UK to Cr, and UCa to Cr ratios were calculated from measured levels of urinary minerals. These were repeated in 11 hypercalciuric patients after 2 weeks of increased potassium intake.

RESULTS

A total of 100 urine samples were analyzed. The UCa/Cr ratio in blacks 0.04 +/- 0.06 (mean +/- standard deviation) was significantly lower than in whites 0.16 +/- 0.12. There were 21 hypercalciuric white children versus only 1 black child. Linear regression analysis revealed a positive direct correlation between UNa/Cr and UCa/Cr in all 100 subjects and in whites alone but not in blacks. An inverse relationship existed between UK/Cr and UCa/Cr in all subjects and in whites and showed a strong trend in blacks. A marked direct relationship was found between UNa/K and UCa/Cr in all subjects (r = .43) as well as in whites (r = .59) and blacks (r = .49). One black child and 10 white hypercalciuric children were treated with "extra" K for at least 2 weeks. The UNa/K decreased from 4.73 +/- 2.28 to 1.98 +/- 1.09, and the UCa/Cr decreased from 0. 31 +/- 0.10 to 0.14 +/- 0.07, with resolution or improvement of the patients' symptoms.

CONCLUSIONS

In our patient population with urinary symptoms, the UCa/Cr ratio in black children is lower and hypercalciuria less common than in white children. In both white and black populations, the UNa/K ratio had the strongest association with the UCa/Cr ratio, indicating an opposing role of UNa and UK on the UCa/Cr ratio. Increased potassium intake was found to be beneficial for hypercalciuric children by decreasing the UNa/K ratio and, consequently, the UCa/Cr ratio.