Urinary calcium excretion in children with vesicoureteral reflux

BACKGROUND

Renal malformations including vesico-ureteral reflux (VUR) are associated with urolithiasis. However, studies on urinary calcium excretion in children with VUR have not been reported. This study was conducted to find out whether children with VUR have a higher prevalence of hypercalciuria and whether their family members are affected by hypercalciuria and/or urolithiasis.

METHODS

We studied the prevalence of hypercalciuria and urolithiasis in 46 children (12 males and 34 females) with VUR and in their parents.

RESULTS

Three out of 46 children had renal colic and nine out of 46 exhibited calyceal microlithiasis in the renal sonography. According to Stapleton's criteria, we found that 27 out of 46 children (58.6%) had hypercalciuria. These children were significantly shorter than children with normal calciuria and showed lower values of maximal urinary osmolality. We found no differences in urinary calcium excretion values related to the VUR grading, or to the presence or absence of renal scars, or to whether VUR was still unresolved or already resolved at the time of study. Seventeen out of 27 children with hypercalciuria (63%) had one or both parents affected by hypercalciuria, and there was a history of urolithiasis in six first-degree relatives and in four second-degree relatives (37%). Besides, 10 out of 19 children without hypercalciuria (52.6%) had one or both parents affected by hypercalciuria and there was a history of urolithiasis in three first-degree relatives and in three second-degree relatives (31.6%). Among the 27 children whose parents had hypercalciuria, four had both parents affected, 19 had only the mother affected and in four patients only the father was affected.

CONCLUSION

Our results showed that the prevalence of hypercalciuria was greater in paediatric patients with VUR than in the general population. Urolithiasis in patients with VUR had a metabolic origin. Hypercalciuria was inherited as an autosomal dominant trait although with a higher probability to be inherited from the mother.

Bone mass and bone modelling markers in hypertensive postmenopausal women

Numerous phosphocalcium alterations associated with bone mineral density in hypertension have been described, but very few studies assess them. This study assesses bone mass in hypertensive postmenopausal women and the hypertension influence determining both calcium homeostasis and bone turnover markers. Blood and urine samples were analysed for calcium metabolism-related parameters. Densitometry studies were conducted in the lumbar spine (L2-L4). Hypertensive osteoporotic women--selected from 82 women, with 22% osteoporosis prevalence, similar to the rate for the same age in the Spanish population--had significantly higher levels of body mass index (29+/-4 vs 26+/-4, P=0.019), calciuria (293+/-146 vs 210+/-116 mg/24 h, P=0.023) and calcium/creatinine ratio (0.33+/-0.2 vs 0.22+/-0.1 P=0.003) vs hypertensive nonosteoporotic women. No relation was found between systolic and diastolic blood pressure with bone mass. However, there was a negative osteocalcin correlation (r=-0.386, P=0.0001, and r=-0.242, P=0.033). Calciuria is associated with bone mass decrease in hypertensive women, and there is no relation between bone mass and blood pressure.

Hypercalciuria in Beckwith-Wiedemann syndrome

We determined the incidence of hypercalciuria (HC) and its association with nephrocalcinosis and nephrolithiasis in 18 consecutive patients with Beckwith-Weidemann syndrome (BWS). Random, nonfasting urine samples were obtained from each patient. All patients had abdominal ultrasonography, most on several occasions. Four patients (22%) had HC. Of these, 2 had nephrocalcinosis, one had hyperechoic kidneys, and one had normal renal imaging. Serum calcium was normal in all patients with HC. Because we found that an increased prevalence in the occurrence of HC and its complications in a group of children with BWS, any child with BWS should be evaluated for HC.

Fatty acids, calcium and bone metabolism

Epidemiological, clinical and experimental evidence suggests that fatty acids may have an effect (due to their chemical structure) on calcium metabolism in animals and man. Fatty acid deficiency in animals can lead to a loss of bone calcium and matrix, resulting in marked bone demineralization, and treatment with a mixture of omega-3 and omega-6 polyunsaturated fatty acids can induce significant reduction in some biochemical markers of bone reabsorption. A relationship, between phospholipid fatty acid content, calcium-regulating hormones and intestinal, renal, and bone calcium metabolism alterations, has been reported in patients with renal stones and hypercalciuria. Recent studies have shown specific effects of fatty acids on the gene expression of some bone cytokines. Fatty acids might be involved in calcium metabolism influencing cellular calcium ion transport directly, as second messengers, or generating, through the cyclooxygenase pathway, potential biological mediators which have complex effects on bone remodeling. Experimental and clinical documentation of the specific and indirect effects of fatty acids on calcium and bone metabolism could open up new and interesting clinical prospects.

Metabolic disorder in myocardiac intracellular free calcium after thermal injury

Cutaneous burn trauma causes functional inhibition of the heart, but the mechanism is unclear. Using a high dissociation constant (K(D)) calcium indicator TF-BAPTA and 19F MR spectroscopy, the relationship between the changes of cytosolic free calcium and cardiac function after burn trauma was examined. Sprague-Dawley rats received scald (43% TBSA) or sham burns. Twenty-four hours later, the hearts were excised and perfused by the Langendorff method with a modified phosphate-free Krebs-Henseleit bicarbonate buffer. Left ventricular developed pressure (LVDP) was recorded through a catheter attached to an intraventricular balloon. At the same time, 31P and 19F nuclear magnetic resonance (NMR) spectroscopy was perforined before and after TF-BAPTA loading. LVDP of the heart from burned rats was 40% less than in sham burn rats (65+/-6 vs 110+/-12 mmHg, P<0.01). Cytosolic free calcium increased about four-fold in those hearts from the burn group compared to the sham burn group (0.807+/-0.192 vs 3.891+/-0.929 microM). Loading TF-BAPTA in those hearts only caused about a 15-20% decrease in LVDP. PCr/Pi ratio also decreased significantly with this loading, but ATP signals were not affected. In conclusion, the inhibition of cardiac contractility caused by burn trauma correlated with the overload of cytosolic free calcium in the heart.

Correlation between 25-hydroxyvitamin D3 1 alpha-hydroxylase gene expression in alveolar macrophages and the activity of sarcoidosis

PURPOSE

To demonstrate expression of the 25-hydroxyvitamin D3 1 alpha-hydroxylase (1 alpha-hydroxylase) gene in human alveolar macrophages and measure the correlations among the 1 alpha-hydroxylase mRNA level, the activity of sarcoidosis, and calcium metabolism.

SUBJECTS AND METHODS

We examined 7 patients with sarcoidosis and 6 control patients with other pulmonary disorders who underwent bronchoalveolar lavage. Levels of 1 alpha-hydroxylase mRNA were measured by semiquantitative polymerase chain reaction amplification. We measured serum levels of calcium, ionized calcium, parathyroid hormone, calcitriol (1,25-dihydroxyvitamin D3), and 25-hydroxyvitamin D3 to evaluate calcium metabolism. To estimate the activity of sarcoidosis, we measured the cell count, the CD4/CD8 ratio in bronchoalveolar lavage cells, and the serum angiotensin-converting enzyme (ACE) activity.

RESULTS

Expression of 1 alpha-hydroxylase was demonstrated in purified human alveolar macrophages. The 1 alpha-hydroxylase mRNA levels in bronchoalveolar lavage cells were fivefold higher in sarcoidosis patients than in control patients (10.8 +/- 3.6 vs. 2.2 +/- 1.4, P <0.003). Among all patients studied, there were significant correlations between the 1 alpha-hydroxylase mRNA level in bronchoalveolar lavage samples and the percentage of alveolar lymphocytes (r = 0.83, P <0.005), the CD4/CD8 ratio (r = 0.77, P <0.02), serum ACE level (r = 0.58, P <0.05), serum ionized calcium level (r = 0.58, P <0.05), and the calcitriol/25-hydroxyvitamin D3 ratio (r = 0.57, P <0.05). In the sarcoidosis patients, a significant correlation was also observed between 1 alpha-hydroxylase mRNA and the percentage of alveolar lymphocytes (r = 0.82, P <0.05).

CONCLUSION

There is a correlation between 1 alpha-hydroxylase gene expression in alveolar macrophages with the activity of sarcoidosis and its associated disturbances in calcium metabolism.

Microgravity inhibits intestinal calcium absorption as shown by a stable strontium test

BACKGROUND

Little is known about the onset and degree of biochemical and functional alterations in calcium metabolism during microgravity.

OBJECTIVE

To evaluate the effect of microgravity on intestinal calcium absorption and calcium-regulating hormones under metabolic ward conditions.

MATERIALS AND METHODS

Fractional calcium absorption (Fc240 in percentage of dose administered) was determined pre-flight, in-flight and post-flight, by use of a stable strontium test in one cosmonaut who spent 20 days in space. Moreover, a sequence of blood samples was collected for the determination of serum parathyroid hormone (PTH), 25-hydroxyvitamin D, calcitriol and serum C-telopeptide (CTx, biomarker of bone resorption) levels. During all periods of data collection, calcium intake was held constant at a minimum level of 1.000 mg day(-1) and a daily supplement of 16.6 microg vitamin D2 was given. Personal ultraviolet (UV) light exposure was measured during the whole mission using a biologically weighting UV dosimeter.

RESULTS

Fc240 was markedly reduced on flight day 19 (4.4%) as compared to pre-flight and post-flight data (13.4% and 17.2%, respectively). Serum calcitriol levels fell from 40.6 pg mL(-1) (mean pre-flight level) to 1.3 pg mL(-1) on flight day 18 and returned into the normal range after recovery. Serum CTx increased during the flight, while serum PTH and 25-hydroxyvitamin D levels did not change significantly.

CONCLUSIONS

Intestinal calcium absorption can be diminished after only three weeks of microgravity. Changes are associated with a severe suppression of circulating calcitriol levels, but are independent of exogenous vitamin D supply and serum PTH levels.

Quantitative determination of parathyroid hypertensive factor by enzyme-linked immunosorbent assay

A new competitive enzyme immunoassay for the detection parathyroid hypertensive factor (PHF) in human plasma using a PHF-horseradish peroxidase conjugate and IgM antibody adsorbed on the microtiter plate was established. The antibodies raised against rat PHF could recognize human PHF. Cross-reactivity of anti-PHF antibodies with other serum haptens and proteins was negligible. Conjugation of PHF with horseradish peroxidase did not neutralize the antigen activity. The limit of detection of PHF was 0.02 U/mL in reference units and PHF levels between 0.02 and 1 U/mL could be detected. Within-run coefficient of variation (CV) was less than 10%, and between-run CV was less than 15% for over the dynamic range of the assay. Preliminary clinical studies were performed with plasma samples from hypertensive patients with confirmed diagnosis. Parathyroid hypertensive factor levels, as detected with this immunoassay, were positively correlated with PHF levels detected with the semiquantitative blood pressure (BP) bioassay previously used. Parathyroid hypertensive factor levels detected with the enzyme-linked immunosorbent assay (ELISA) were also correlated with BP in patients. The PHF ELISA provides a selective, simple, and rapid method that can be used for routine determination of PHF in human plasma, and provides useful clinical information.

Changes in renal hemodynamics and tubular function of surgically cured primary hyperparathyroid patients are probably due to chronic hypercalcemic nephropathy

To understand the mechanisms responsible for the persistent hypercalciuria and reduced glomerular filtration rate (GFR) previously found in 6 of 10 patients surgically cured of primary hyperparathyroidism (PHPx), the tubular handling of lithium, sodium, calcium, and phosphate as well as the renal hemodynamics were evaluated in these 10 PHPx patients, in 10 control subjects, and in 5 patients with renal hypercalciuria (RH), during fasting and after an oral calcium load. A positive correlation between the fractional excretions of calcium and sodium was found in all groups, but the PHPx patients excreted more calcium for the same amount of sodium than control subjects. The fractional proximal sodium reabsorption (FPRNa), distal delivery, and fractional phosphate reabsorption were similar in all groups; a significant positive correlation was found between the fractional calcium reabsorption and the FPRNa, indicating that proximal tubular function was preserved and that the urinary calcium losses in RH and in the hypercalciuric PHPx patients (h-PHPx) occurred in the distal nephron. However, only h-PHPx patients had reduced renal plasma flow, renal blood flow, and GFR, as well as a high renal vascular resistance, which was even more evident after the calcium challenge. These findings lead us to conclude that RH and h-PHPx patients are very different, as far as kidney dysfunction is concerned, and that a hypercalcemic nephropathy is the most probable cause of the alterations in distal calcium reabsorption and renal hemodynamics found in the h-PHPx patients.

High prevalence of bone disorders after gastrectomy

BACKGROUND

Studies indicate that gastrectomy might alter calcium and bone metabolism, resulting in bone disorders. No data are currently available on the prevalence of bone disorders after gastrectomy.

METHODS

Sixty gastrectomy patients were investigated for serum parameters of calcium and bone metabolism 5 to 20 years postoperatively and compared to an age- and sex-matched healthy control population. Forty patients agreed to a radiological investigation of the spine by anterior-posterior and lateral radiographs of the thoracic and lumbar spine and by computed tomography (CT) osteodensitometry.

RESULTS

Serum calcium and 25-(OH)-vitamin D were decreased in gastrectomized patients, while parathyroid hormone and 1,25-(OH)2-vitamin D were increased. Serum parameters of calcium metabolism were altered in as many as 68% of patients. We found 31 vertebral fractures in 13 patients, 30 grade 2 vertebral deformities in 18 patients, and osteopenia in 15 patients, corresponding to a prevalence of 33%, 45%, and 37% in gastrectomized patients, respectively. The overall rate of gastrectomy patients having vertebral fractures and/or osteopenia was 55%. The risk of having a vertebral deformity was increased by more than sixfold after gastrectomy. Our study is the first report evaluating vertebral deformities in gastrectomized patients, and the largest series of gastrectomized patients investigated by CT osteodensitometry.

CONCLUSION

We found a high prevalence of bone disorders in gastrectomized patients, possibly resulting from disorders in calcium metabolism. Postgastrectomy bone disease might derive from a calcium deficit, which increases calcium release from bone and impairs calcification of newly build bone matrix.

[The use of xidifon for the correction of phosphorus-calcium metabolism in patients in the terminal stage of chronic kidney failure who are on programmed hemodialysis]

Correction of impaired phosphoric-calcium metabolism was performed in 15 hemodialysis patients with terminal chronic renal failure (TCRF). For this purpose a synthetic analogue of pyrophosphoric acid xidiphone produced in Russia was used (2% aqueous solution 1 tablespoon 3 times a day 0.5 h before meal for 2-3 months). Prior to and in the course of xidiphone treatment all the patients received calcium gluconate (1 g x 3 daily), polyvitamins, on-demand digoxine. Measurements of serum concentrations of urea, potassium, sodium, total calcium, alkaline phosphatase activity demonstrated xidiphone-related normalization of serum total calcium, serum activity of alkaline phosphatase, a mild rise of sodium. The results say in favor of using xidiphone in the TCRF patients.

[Hypercalciuria: etiologies and treatment]

Hypercalciuria is a rare biological symptom with multiple possible etiologies in children. Normal calcium excretion rate in children is defined as lower than 4 mg/kg per day, significantly higher values being observed in infants. When using urinary calcium: creatinine ratio, normal values are below 0.22 mg/mg in children, and below 0.6 to 0.8 mg/mg in infants. In our experience half patients with hypercalciuria have idiopathic hypercalciuria. Idiopathic hypercalciuria can be hereditary with a dominant autosomal mode of inheritance. Its pathophysiology is unclear, increased calcium intestinal absorption and impaired renal tubular calcium reabsorption being the two main underlying anomalies. Patients with hypercalciuria should be informed about the risk of urolithiasis and its possible prevention by a high water intake. In those patients with nephrocalcinosis or recurrent episodes of lithiasis, hydrochlorothiazide can be effective in reducing hypercalciuria. However, adverse effects of hydrochlorothiazide on serum lipids have been recently reported and make this treatment questionable in the long term.

[Studies of calcium metabolism in patients with hypercalciuria]

The different subgroups of hypercalciuria cannot be separated clearly by the Pak calcium-load test. To improve the diagnosis and therapy we examined all relevant parameters of calcium metabolism in 32 patients with calcium urolithiasis and hypercalciuria (> 6.25 mmol/day). We also conducted bone mineral density measurements as well as the Pak calcium-load test. In most cases the pathophysiological constellations which Pak takes as the basis for his classification of hypercalciuria could not be shown. To date, diagnostics only insufficiently explains the genesis of hypercalciuria (except pHPT). As a consequence, a therapeutic problem arises: a low-calcium diet should not be generally recommended, since some patients may develop osteopenia. From our investigation the following diagnostic and therapeutic conclusions can be drawn: (1) Hypercalciuria in primary hyperparathyroidism should be treated by surgical removal of the adenoma. (2) The parathormone-independent osteogenic form should be treated with thiazides. (3) Hypercalciuria with increased 1.25-dihydroxyvitamin D should be treated by low-calcium diet.

Non-malignant complications of coeliac disease

Patients with coeliac disease are at increased risk of developing complications which increase morbidity and mortality. Emphasis on malignant complications has often overshadowed the non-malignant risks, which have received relatively little attention, although some of these can be very troublesome and even life-threatening. This article points out that a large population of unidentified or neglected coeliac patients is at potential risk. The challenge is to identify this group by case-finding or screening programmes in selected populations, so that they can be offered a gluten-free diet and other treatments which will not only improve general health but may also prevent or reduce the development of health problems. The non-malignant risks are outlined and bone and neuropsychiatric disturbances considered in more detail because of recent developments in these areas.

The cause of maintained hypercalciuria after the surgical cure of primary hyperparathyroidism is a defect in renal calcium reabsorption

The hypercalciuria that eventually remains after the successful removal of a solitary parathyroid adenoma may originate from excessive intestinal calcium absorption, bone resorption or deficient renal reabsorption. In order to clarify this question, ten patients surgically cured from primary hyperparathyroidism (PHPx), ten age-matched normal subjects and five nephrolithiasic patients with renal hypercalciuria (RH) were studied after five days on a low calcium diet, either during fasting or after oral calcium load. Fasting serum calcium, amino-terminal and intact PTH levels and also urinary cAMP excretion were normal in every individual patient. Serum ionized calcium and inulin clearance (GFR) were used for calculations of the filtered load (FL Ca) and the fractional excretion of calcium (FE Ca). Six PHPx patients displayed fasting calciuria above the upper limit calculated for control subjects, despite having the lowest GFR and FL Ca (p < 0.05 vs control). These patients (h-PHPx) had a small calciuric response to oral calcium load. Serum 1,25-(OH)2D3 and 25OHD3 did not correlate with calciuria. Our findings exclude intestinal hyperabsorption and excessive bone resorption in h-PHPx patients, and strongly suggest a renal tubular defect in calcium reabsorption as the cause of their hypercalciuria. This defect could be primary, as in RH, but only three hPHPx patients had recurrent kidney stones before surgery. On the other hand, as a negative correlation between GFR and FE Ca was only found in PHPx patients, it seems probable that the disturbances in glomerular and tubular functions were secondary to the long standing hypercalcemic hyperparathyroidism.

Investigation of calcium disorders

The advent of new two-site immunometric assays for intact parathyroid hormone (PTH) measurement has enhanced the interpretation of results in many patients under investigation for hypercalcemia. The aim of this article is to give practical advice on the use of the new intact PTH methods and other tests for the investigation of the more common disorders of calcium metabolism.

Aetiology of nephrolithiasis in north Indian children

The aetiology of nephrolithiasis was investigated in 32 north Indian children (25 boys, 7 girls, mean age 7.9 +/- 3.3 years). An underlying disorder was detected in 16 (50%) patients and included idiopathic hypercalciuria (8 patients), hyperoxaluria (3 patients) and renal tubular acidosis, primary hyperparathyroidism and hyperuricosuria (1 patient each). Magnesium ammonium phosphate calculi were found in 2 patients with recurrent urinary tract infections, 1 of whom had a duplex pelvic collecting system. In 16 patients (50%) a cause for renal calculi was not identified. Our findings suggest that an underlying disorder is present in a large proportion of children with nephrolithiasis where appropriate treatment may be beneficial.

Boucher-Neuhauser syndrome associated with hypocalciuric hypercalcemia

A 52-year-old woman was diagnosed as having cerebellar ataxia, hypogonadotropic hypogonadism and retinochoroidal degeneration, the so-called, "Boucher-Neuhauser" syndrome proposed by Limber et al (Am J Med Genet 33:409, 1989). In addition, laboratory findings showed the elevation of serum calcium (Ca) levels, low urinary Ca excretion, and exaggerated reabsorption of filtrated Ca (FECa:0.14%), suggesting complication of hypocalciuric hypercalcemia. This is a very rare case of Boucher-Neuhauser syndrome associated with hypocalciuric hypercalcemia.

Calcium and phosphorus derangements

Derangements in plasma calcium and phosphorus concentrations can precipitate serious and life-threatening complications in critically ill patients. An understanding of the function and homeostasis of these ions is essential to fully comprehend the causes, clinical manifestations, and treatment of calcium and phosphorus imbalances. This article will help the critical care nurse to identify patients at risk, to recognize derangements early (while they are still mild), and to seek and monitor appropriate treatment.