Urinary Calcium Excretion Rate Research Articles

Dietary potassium effects on renal calcium transport at single nucleus resolution

Calcium homeostasis is maintained by the coordination of the intestines, bones, and kidneys. Dietary calcium is absorbed in the intestines, enters the bloodstream, and eventually finds its place in the bone reservoir or undergoes filtration by the glomerulus before being reabsorbed throughout the nephron. The late distal convoluted tubule (DCT2) and connecting tubule (CNT) determine the final rate of urinary calcium excretion, since no calcium reabsorption takes place beyond the connecting tubule (CNT). When excess calcium is excreted in the urine, also known as hypercalciuria, it contributes to the development of osteoporosis and the formation of kidney stones. High dietary potassium intake is strongly associated with a lower risk of kidney stone formation. Yet, the precise mechanism by which potassium intake modulates calcium excretion is not clear. To examine the transcriptional changes linking high dietary potassium intake and calcium transport, we applied single-nucleus RNA-sequencing (snRNA-Seq) in enriched distal nephron cells. To achieve the enrichment, we crossed a Calbindin 1 (Calb1)-driven Cre mouse line with the INTACT (for Isolation of Nuclei TAgged in Specific Cell Types) reporter line, which allows the GFP reporter to be expressed at the nuclear envelope of all calbindin 1-expressing cells. As the Calb1-Cre is constitutively expressed, all cells that have calbindin 1 expression at any time point during development will express the reporter. We examined the GFP expression by immunofluorescence, and found that it is expressed along the entire distal nephron from the distal convoluted tubule (DCT), CNT, to the collecting duct (CD). Male Calb1-Cre-INTACT mice were provided either a normal (NK, 1.05%) or a high (HK, 2%) potassium diet for 4 days and kidneys were snap-frozen for targeted snRNA-Seq using 10X Chromium (n=3 mice per group, targeting 10,000 nuclei per mouse). Our snRNA-seq dataset showed 6 major clusters, including DCT (DCT1 and DCT2), CNT (3 subclusters), CD principal cells (3 subclusters), ɑ-intercalated cells (2 subclusters), β-intercalated cells (2 subclusters), and proliferating cells. We curated a calcium score from the expression of known calciotropic genes ( Slc8a1, Vdr, Trpv5, Calb1, S100g, Ryr2, Trpv6) and used it as an index of calcium handling capacity. The calcium score is the highest in DCT2 and CNT along the distal nephron. In all CNT subclusters of the HK-treated animals, the calcium score is higher compared to the NK-treated animals, suggesting more calcium transport in CNT. Given that HK stimulates aldosterone and causes CNT hypertrophy, we compared the results with mice subjected to low dietary potassium (LK) treatment and metolazone (thiazide) treatment. The aim was to delineate the effects of dietary potassium and aldosterone A comprehensive summary of plasma potassium levels, urinary calcium excretion, aldosterone levels, calcium scores, and CNT morphology has been presented in the table below. Notably, the comparative analysis reveals a significant correlation between aldosterone levels and CNT size, both of which exhibit an inverse relationship with urinary calcium excretion: [Formula: see text] Our results suggest that DCT2 and CNT are the major sites for calcium transport. Yet, CNT exhibit more heightened adaptability in response to physiological or pharmacological perturbations at both transcriptional and morphological levels. Calcium homeostasis coincides with the regulation of aldosterone levels and CNT remodeling. DK51496 and DK133220 to DHE; K01DK121737 and AHA 20CDA35320169 to JWN. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Обмен кальция и остеопороз у больных ишемической болезнью сердца в пожилом и старческом возрасте

im. To analyze the relationship between calcium and various clinical and laboratory parameters in old and very old patients with coronary artery disease (CAD) based on the determination of the blood concentration of ionized calcium and daily excretion of calcium in the urine. Materials and methods. This work was a cross-sectional study enrolled 102 patients (84 women and 18 men) with coronary artery disease with a mean age of 83.0±5.9 years. The blood level of ionized calcium (N 1.16–1.32 mmol/l), daily excretion of calcium in the urine (N 2.5– 7.5 mmol/l) and concentration of 25-hydroxycalciferol (25(OH)D) were determined in all patients. Along with this, the bone mineral density of the lumbar spine and proximal femur was analyzed using dual-energy x-ray absorptiometry. Results. The mean daily excretion of calcium in the urine was 1.39±1.1 mmol/l (0.17–7.44 mmol/l). 84.4% of patients had low calcium content in daily urine. The mean blood concentration of ionized calcium was 1.26±0.05 mmol/l (1.16–1.53 mmol/l). Hypercalcemia was observed in 8.3% of patients. Osteoporosis in the proximal femur was registered in 32.9% of patients, in the lumbar spine – in 18.1% of patients. In patients with normal vitamin D level the mean urinary calcium excretion was 1.77±1.2 mmol/l, with vitamin D deficiency – 1.1±0.7 mmol/l (p=0.07). In patients with low calcium excretion in the urine, the mean blood concentration of vitamin D was 18.7±7.7, with normal excretion – 28.5±10.8 ng/ml (p=0.007). Significant inverse relationships were registered between urinary calcium excretion and creatinine (r=-0.36; p<0.0001). In the group of patients with low urinary calcium excretion the mean creatinine level reached 102.3±23.9 µmol/l, with normal excretion – 84.9±11.2 µmol/l (p<0.0001). There was a significant direct correlation between daily urinary calcium excretion and glomerular filtration rate, estimated using the CKD-EPI formula (r=0.39; p<0.0001) and an inverse correlation between blood calcium and GFR (r=-0.26; p=0.01). Significant direct relationship was registered between the blood concentration of ionized calcium and the creatinine (r=0.2; p=0.05) and urea (r=0.32; p=0.04) concentration. Conclusion. The study results demonstrate a low level of calcium excretion in the urine in old and very old patients with coronary artery disease. The urine calcium excretion is primarily due to impaired renal function and low vitamin D concentration.

Effect of Herbal Formulation “Cystone®” on Urolithiasis

Context: The study aimed to systematically review the clinical data on the efficacy of Cystone® as an herbal treatment for urolithiasis. Methods: Full text randomized clinical trials comparing Cystone® with placebo or citrate in patients with urolithiasis for urinary stone prevention or treatment were evaluated. Three databases, including PubMed, Scopus, and Cochrane Library, were searched from January 2000 to December 2017. The main outcomes were the reductions in calculi number/size and urinary excretion rate of calcium, oxalate, and urate. The secondary outcome was the adverse effects of Cystone®. Documents were screened by two reviewers for eligibility. The Jadad score was used for quality assessment. The data were analyzed using the comprehensive meta-analysis version 2.2.064 software. Results: Of 532 relevant studies, five were finally included. Cystone® was effective in the decrement of stone size in comparison with placebo (95% CI: 0.63, 9.13). There was a significant difference in the excretion rate of uric acid but not calcium compared to the placebo. Cystone® had no significant side effects. Conclusions: Cystone® is more effective than a placebo in the treatment of urinary tract stones. It significantly induces stone size decrement and clearance compared to placebo. The low quality of reports is a major limitation in the applicability of these results.

Effectiveness of Daily Urinary Excretion of Minerals as an Indicator of Dietary Mineral Intake: Effect of Absorption-Promoting or Inhibiting Factors in Foods on Daily Urinary Excretion Rate of Calcium, Magnesium and Zinc in Young Women

Effectiveness of Daily Urinary Excretion of Minerals as an Indicator of Dietary Mineral Intake: Effect of Absorption-Promoting or Inhibiting Factors in Foods on Daily Urinary Excretion Rate of Calcium, Magnesium and Zinc in Young Women

Urinary stone risk factors in the descendants of patients with kidney stone disease.

Evidence has indicated that immediate family members of nephrolithiasis patients had high opportunity to develop stones. However, they are usually not regarded to be at risk, since it is unclear if there are any lithogenic abnormalities found in non-stone-forming nephrolithiasis relatives. Our aim was to investigate urinary metabolic abnormalities in the children of nephrolithiasis patients, compared with the general population. The 24-h urinary metabolic profile was studied for 28 calcium oxalate nephrolithiasis patients (NL) and 46 of their descendants (ND), as well as 40 non-stone-forming volunteers (V) and 34 of their descendants (VD). There was no difference between age, gender, and serum creatinine between NL vs. V (parental groups) and ND vs. VD (descendant groups). High urinary oxalate in nephrolithiasis and urinary calcium in their descendants was detected. In addition, an elevated urinary excretion rate of calcium, phosphate, protein, and albumin, along with low citrate excretion and high urinary supersaturation was observed in both the nephrolithiasis patients and their descendants. Approximate 17.8-24.4% of the nephrolithiasis descendants had a urinary supersaturation higher than the nephrolithiasis level, but none was found in VD group. The level of urinary supersaturation index was correlated with urinary protein and albumin excretion in nephrolithiasis family. It was demonstrated that nephrolithiasis offspring carried several urinary metabolic risks predisposing to stone formation which are similar to their parents, and about one in every five nephrolithiasis children had nephrolithiasis level urinary supersaturation.

Prevalence of idiopathic hypercalciuria in children with urinary system related symptoms attending a pediatric hospital in Bandar Abbas in 2014

BackgroundIdiopathic hypercalciuria is a group of diseases which can be manifested with urinary symptoms. Its importance is due to high prevalence, recurrent infections, and stone formations which are often asymptomatic.ObjectiveThe objective of this study was to determine the prevalence of idiopathic hypercalciuria in children with urinary system related symptoms in Bandar Abbas in 2014.MethodsThis descriptive cross-sectional study was done in 2014 in a children’s hospital in Bandar Abbas (southern Iran) on 321 children who were between 2 months to 14 years old. Random morning urine sample was obtained from all the patients, and calcium to creatinine ratio was assessed for all the patients for two times. Hypercalciuria is defined as urinary calcium excretion rate that is greater than 4 mg/kg per 24 hours in a child older than two years of age. Data was analyzed using IBM SPSS statistics 23.0 software and Chi-square and independent-samples t-test.ResultsAmong the 321 children assessed, 153 (47.7%) had idiopathic hypercalciuria. The mean age of the children with idiopathic hypercalciuria was 55.20±43.71. Prevalence of idiopathic hypercalciuria was 48.3% in children with urinary tract infection, 54.9% and 53.6% in children with microscopic and macroscopic hematuria respectively, In children with dysuria, there were 52.1%, and 51.8% in children with frequency, 49.1% in children with kidney stone which was confirmed with sonography, 28.6% and 37.5% in children with nocturnal and daily urinary incontinency respectively. Results of this study showed no significant relationship between urinary system symptoms and idiopathic hypercalciuria (p>0.05).ConclusionHypercalciuria can be presented with different symptoms associated with urinary symptoms. Therefore, it is recommended to check the urinary calcium level in children with urinary symptoms with no definite etiology.

Serum Cortisol and the Risk of Osteoporosis in Nigerians on Medroxyprogesterone Acetate

Depo-Provera®; Depot-Medroxyprogesterone Acetate (DMPA) is one of the most used contraceptives and it is currently used by more than 30 million women in most of developed and developing countries. The study was designed to investigate the relationship between serum cortisol and the risk of osteoporosis in Nigerians using Depo-Provera®. We investigated 50 women using Depo-Provera® and 50 age-matched control, not on DPMA. Serum cortisol, progesterone, estrogen, estradiol, serum calcium, cathepsin K and urinary excretion rate of calcium were determined in subjects and controls. Serum cortisol and cathepsin K were significantly higher in women using DPMA Vs controls (P<0.01), we also found a significantly lower estradiol, serum calcium and an increased urinary excretion rate of calcium in subjects using DPMA as compared to controls (P<0.05). We found a positive correlation between serum cortisol and serum calcium (r=0.553) (P<0.01), serum cortisol and cathepsin K (r=0.568, P<0.05). Our study shows that hypercortisolaemia may be responsible for calcium loss, further investigation is needed to determine if cortisol induced calcium loss is responsible for bone demineralization associated with the use of DPMA.

Hypercalciuria following ceftriaxone a fact or myth.

Introduction: Nephrolithiasis is a common worldwide problem both in children and adults. Ceftriaxone as a widely used antibiotic can contribute to the formation of renal stones and hypercalciuria. Objectives: To find the effect of ceftriaxone, a widely used antibiotic, on urinary calcium excretion rate in children. Patients and Methods: 84 infants and children over 3 months admitted to hospital for non-renal problems. They were all previously healthy children affected with a condition mandating hospitalisation. They were randomly divided into 2 groups; those who received ceftriaxone according to their physician decision as the case group and those who did not receive antibiotics as the control group. The patients urinary calcium excretion was determined as calcium to creatinine ratio in a random urine sample in the first and third day of their admission. All data was expressed by mean ± SD and analysed by t independent and chi-square tests by SPSS 16. P P value less than 0.05 was significant. Results: Eighty-four cases were analysed. Calcium excretion in received and non-received ceftriaxone groups was 0.13 ± 0.06 and 0.14 ± 0.02 respectively at first day of admission ( P = 0.1). After 3 days, the urine calcium to creatinine ratio increased to 0.27 ± 0.2 and 0.26 ± 0.08 in received and non- received ceftriaxone groups ( P = 0.8). Conclusion: In children, urinary calcium excretion increases 2 times in average in a short time after admission because of gastroenteritis, and ceftriaxone is not different to other antibiotics for increase urinary calcium excretion in 3 days after admission.

MP20-06 OVERNIGHT PRECIPITATION RISK STUDY

You have accessJournal of UrologyStone Disease: Basic Research I1 Apr 2014MP20-06 OVERNIGHT PRECIPITATION RISK STUDY Mohammad Shafiee Nyestanak, Mitchell Halperin, Mehdi Aarabi, Alexander Logan, and Ali Vahidirad Mohammad Shafiee NyestanakMohammad Shafiee Nyestanak More articles by this author , Mitchell HalperinMitchell Halperin More articles by this author , Mehdi AarabiMehdi Aarabi More articles by this author , Alexander LoganAlexander Logan More articles by this author , and Ali VahidiradAli Vahidirad More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2014.02.728AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Restful sleep is essential for the normal functioning of our body and should not be interrupted by an urge to void. In order to achieve this goal, the urine flow rate (UFR) should be low in this period. Conceivably, a lower urine volume may lead to supersaturation of lithogen in the renal collecting system. Some authors suppose that the overnight period is a time of maximal urinary precipitation risk and perhaps a target for specific clinical intervention. The aim of this study is to define the urinary composition and excretion rate of calcium, phosphate, pH, and recognize the likelihood of supersaturation, when the urine flow rate is at nadir overnight. METHODS 26 subjects’ urine sample every 2-3 hours during daylight and one nocturnal were collected. Subjects’ urine flow rate was calculated in each collection. Urinary constituents for calcium phosphate precipitation including electrolytes, calcium, phosphate, citrate, and pH were measured. Urine sodium and potassium were measured by flame photometry. Chloride was measured by electromimetic titration. Osmolality was measured by freezing point depression. Comparisons within individuals were done by paired t test. RESULTS Total urine phosphate concentration rose significantly overnight (daytime 18.7 ± 1.4 umol/min vs nocturnal 20.9 ± 1.7 umol/min). Calcium excretion rate fell significantly overnight (from 2.4 ± 0.2 umol/min to 1.5 ± 0.3 umol/min, P <0.05), in parallel with sodium excretion (54 ± 16 umol/min from its daytime 127 ± 12 umol/min, P <0.05), preventing nocturnal calcium concentration from increasing (3.0 ± 0.3 mmol/l daytime to 2.5 ± 0.5 mmol/l overnight). CONCLUSIONS This study clearly showed that there is no significant change in calcium concentration overnight. Even though total phosphate concentration rises significantly, there is no significant change in divalent phosphate concentration. In conclusion, although UFR is lower overnight, there is no evidence that risk of calcium phosphate precipitate formation will increase. © 2014FiguresReferencesRelatedDetails Volume 191Issue 4SApril 2014Page: e198 Advertisement Copyright & Permissions© 2014MetricsAuthor Information Mohammad Shafiee Nyestanak More articles by this author Mitchell Halperin More articles by this author Mehdi Aarabi More articles by this author Alexander Logan More articles by this author Ali Vahidirad More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Association of Serum Calcium and 24 Hours Urinary Excretion of Calcium in Patients of Preeclampsia

Preeclampsia is a leading cause of fetal growth retardation, infant morbidity, mortality and maternal death. Several biochemical changes occur during the course of the disease, among them serum total calcium and 24 hr urinary calcium excretion rate have drawn remarkable attention. A case control study was designed to see the association of serum calcium and 24 hours urinary excretion of calcium in patients of pre- eclampsia. The study was done from July 2008 to June 2009 in the Department of Biochemistry, Dhaka Medical College, Dhaka. Total 60 subjects were selected as study population. Among them 30 were diagnosed case of preeclampsia and 30 were age- and sex-matched normal pregnant female healthy control. It was found that the mean measured serum calcium level in case group were 1.96 ±0.17 ( mean±SD ) mmol / l and that of control group were 2.34±0.12 (mean±SD) m mol/ l respectively. The mean 24 hr urinary calcium excretion level were 94.40 ±10.68mg/24 hr (mean±SD) in case group and that of control group were 154.35±66.68 (mean ±SD) mg / 24 hr respectively. The study suggests that low level of serum calcium and urinary excretion of calcium was associated with Pre-eclampsia. DOI: http://dx.doi.org/10.3329/bjmb.v3i2.13813 Bangladesh J Med Biochem 2010; 3(2): 57-60

Urinary oxalate and calcium excretion by dogs and cats diagnosed with calcium oxalate urolithiasis

Urine concentrations of oxalate and calcium play an important role in calcium oxalate (CaOx) urolith formation in dogs and cats, with high excretions of both substances increasing the chance of...

Dietary and animal-related factors associated with the rate of urinary oxalate and calcium excretion in dogs and cats

This paper reports the results of a cohort study and randomised clinical trial (RCT) in cross-over design. In the cohort study, the range of urinary oxalate (Uox) and calcium (Uca)...

Serum total estrogen levels and urinary excretion of calcium and hydroxyproline in premenopausal and postmenopausal Chinese women.

Ruey-Jian Chen, MD1 Abstract The study subjects included 26 normal young women with regular menstruation cycles and 30 postmenopausal women. The blood and fasting morning urine samples of premenopausal women were taken between the 4th to 11th day of menstrual cycle. In postmenopausal women the blood and urine specimens were taken at least one year after natural menopause, two months after surgical castration, and two months after completion of radiation therapy for cervical cancer. Serum total estrogen level was measured by radioimmunoassay. The urine hydroxyproline concentration was determined by Kivirikko's method. The mean concentrations of serum total estrogens levels were 185.5 pg/ml and 71.7 pg/ml in premenopausal and postmenopausal women respectively. The mean values of urinary calcium/creatinine (Ca/Cr) molar ratio in premenopausal and postmenopausal women were 0.139 and 0.249 respectively. The mean value of hydroxyproline/creatinine (HOPr/Cr) molar ratio was 0.012 in premenopausal women and 0.028 in postmenopausal women. The parameters of bone loss, such as Ca/Cr ratio and HOPr/Cr ratio, are inversely related with the circulating total estrogen concentration. Therefore, decreased endogenous estrogen production seems to be the major pathophysiologic basis for the enhanced rate of urinary calcium and hydroxyproline excretion in Chinese postmenopausal women.

Glucocorticoids and body fat associated with renal uric acid and oxalate, but not calcium excretion, in healthy children

In patients with hypercortisolism, who are frequently obese, the prevalence of elevated urinary excretion rates of the potential lithogenic factors (calcium, oxalate, and uric acid) is increased. We examined whether the 24-hour urinary excretion rates of calcium, oxalate, and uric acid are already associated with body fat and endogenous glucocorticoids in healthy free-living children, taking relevant nutritional and acid-base factors into account. Urinary analyte excretions were determined in 24-hour urine samples of 300 healthy children aged 4 to 14 years. Potentially bioactive free glucocorticoids were assessed as urinary free cortisol + urinary free cortisone. Associations of glucocorticoids and percentage body fat with the outcome variables were examined in regression models adjusted for sex, height, growth velocity, urinary volume, net acid excretion, and relevant nutritional factors. Percentage body fat and urinary free cortisol + urinary free cortisone explained most of the growth-independent variation of urinary uric acid and also a relevant part of oxalate, but none of calcium. Net acid excretion, an indicator of endogenous acid production, and dietary protein, salt, and fiber intakes were also variably associated with the outcomes urinary calcium, oxalate, and uric acid. In conclusion, body fatness and potentially bioactive free glucocorticoids (even in the physiologic range) appear to affect urinary excretion rates of oxalate and uric acid, whereas urinary calcium output is more strongly related to dietary factors in healthy children. Our data provide the first in vivo–based evidence that the obesity- or hypercortisolism-associated urolithiasis may be a pathophysiologic continuation of the corresponding endocrine metabolic variations in healthy children.

Whole-body vibration can reduce calciuria induced by high protein intakes and may counteract bone resorption: A preliminary study

Excess protein intake can adversely affect the bone via an increase in calcium excretion, while suitable mechanical loading promotes osteogenesis. We therefore investigated whether vibration exposure could alleviate the bone mineral losses associated with a metabolic acidosis. Ten healthy individuals aged 22 – 29 years (median = 25) underwent three 5-day study periods while monitoring their dietary intake. The study consisted of recording the participants' usual dietary intake for 5 consecutive days. Participants were then randomly divided into two groups, one of which received a protein supplement (2 g · kg−1 body mass · day−1; n = 5) and the other whole-body low-magnitude (3.5 g), low-frequency (30 Hz) mechanical vibration (WBV) delivered through a specially designed vibrating plate for 10 min each day (n = 5). Finally, for the third treatment period, all participants consumed the protein supplement added to their normal diet and were exposed to WBV exercise for 10 min per day. Daily urine samples were collected throughout the experimental periods to determine the excretion of calcium, phosphate, titratable acid, urea, and C-telopeptide. As expected, when the participants underwent the high protein intake, there was an increase in urinary excretion rates of calcium (P < 0.001), phosphate (P < 0.003), urea (P < 0.001), titratable acid (P < 0.001), and C-telopeptide (P < 0.05) compared with baseline values. However, high protein intake coupled with vibration stimulation resulted in a significant reduction in urinary calcium (P = 0.006), phosphate excretion (P = 0.021), and C-telopeptide (P < 0.05) compared with protein intake alone, but did not affect titratable acid and urea output. The participants showed no effect of WBV exercise alone on urinary excretion of calcium, phosphate, urea, titratable acid, or C-telopeptide. The results indicate that vibration stimulation can moderate the increase in bone resorption and reduction in bone formation caused by a metabolic acidosis.

Effect of acute acid loading on acid–base and calcium metabolism

To investigate the acid-base and calcium metabolic responses to acute non-carbonic acid loading in idiopathic calcium stone-formers and healthy males using a quantitative organ physiological approach. Five-h ammonium chloride loading studies were performed in 12 male recurrent idiopathic calcium stone-formers and 12 matched healthy men using a randomized, placebo-controlled, cross-over design. Arterialized capillary blood, serum and urine were collected hourly for measurement of electrolytes, ionized calcium, magnesium, phosphate, parathyroid hormone and acid-base status. Concentrations of non-metabolizable base (NB) and acid (NA) were calculated from measured concentrations of non-metabolizable ions. The extracellular acid-base status in the stone-formers during basal conditions and acid loading was comparable to the levels in the healthy controls. The stone-formers tended to have lower renal excretion rates of NA during acid loading; however, for a given degree of non-carbonic acidosis, controls and stone-formers excreted approximately the same amount of NA in the urine, suggesting that the capacity of tubular regeneration of NB was comparable in the two groups. Acid loading resulted in significantly increased concentrations of ionized calcium in serum in both controls and stone-formers. The increase in serum ionized calcium in response to acid loading was, however, significantly higher in the calcium stone-formers than in the healthy individuals. Acid loading resulted in massive calciuria in both groups, with significantly higher urinary calcium excretion rates in the stone-formers compared to the healthy subjects. Renal excretion rates of NA correlated significantly with renal calcium excretion rates in both groups. However, the stone-formers excreted significantly more calcium in the urine at a given rate of renal NA excretion. The hypercalciuric and hypercalcaemic responses to loading with non-carbonic acid are more pronounced in recurrent idiopathic calcium stone-formers than in healthy individuals. Acid loading (i.e. protein ingestion) may contribute to disturbed bone metabolism in idiopathic calcium nephrolithiasis as well as calcium stone formation.

Bioavailability of Calcium: Comparison of Calcium Carbonate and Milk and the Effect of Vitamin D, Age, and Sex Using 24-Hour Urine Calcium as a Method

The aim of the present study was to compare the bioavailability of calcium from calcium carbonate and milk and to investigate if 1,200 IU of cholecalciferol a day increased intestinal absorption of calcium. Both young women and a group of older persons of both sexes were included to study the influence of age and sex. In total, 53 healthy women and men were included: a group of 23 younger women (median age 30) and an older group of 15 women and 15 men (median age 66). The study period was 4 weeks; each participant completed four treatment regimens randomly: CaCO(3), CaCO(3 )+ 1,200 IU of cholecalciferol, milk, and placebo. All regimens were distributed three times a day and consisted of 1,200 mg of elementary calcium. The 24-hour urine calcium excretion was used as a method. Total urinary calcium excretion rates (mmol/day) were as follows (mean +/- SD): placebo 4.41 +/- 2.17, milk 5.17 +/- 2.33, CaCO(3) 5.83 +/- 2.03, and CaCO(3 )+ D 6.06 +/- 2.46. All regimens compared to placebo were significant. Addition of cholecalciferol to the CaCO(3) regimen increased calcium excretion but insignificantly: 0.27 +/- 2.84 mmol/day. The increase in calcium excretion during the milk regimen was significant only for the old group: 0.96 vs. 0.28 mmol/day. No other difference was found according to age and sex. The bioavailability of calcium carbonate and milk was demonstrated. Additional cholecalciferol (1,200 IU) to individuals in positive calcium balance with serum 25(OH)D levels >50 nmol/L only marginally increased calcium absorption in a short-term intervention.

Calciuria and preeclampsia: A case-control study

Objective The aim of this study was to compare calciuria of preeclamptic cases to normotensive controls among pregnant women hospitalized in the French West Indies obstetrics department. Study design This case-control study included 47 preeclamptic women and 50 controls. The main outcome was 24 h urinary calcium excretion rate. Serum levels of creatinine, calcium and uric acid were also analyzed. A logistic regression analysis has been performed to investigate the relationship between hypocalciuria and preeclampsia after having taken into account prognostic preeclampsia factors and pertinent clinical criteria. Results Women with preeclampsia had significantly lower calciuria than normotensive patients (1.5 mmol/24 h ± 1.0 versus 6.0 mmol/24 h ± 4.2, p = 0.0001). After taking into account gestational age at hospitalization, body mass index and nulliparity, hypocalciuria was significantly associated with preeclampsia (ORa = 21.74; 95% CI, 6.9–66.7). The diagnosis value of a calciuria less than 2.1 mmol/24 h is interesting because of its negative predictive value (97%), but its positive predictive value is weak (42%). Conclusion In our population, preeclamptic women had a calciuria significantly lower than controls.

Neonatal transient renal failure with renal medullary hyperechogenicity: clinical and laboratory features

Sonographic findings of renal medullary hyperechogenicity have been observed in the neonate in association with severe perinatal renal injury, kidney malformations or nephrocalcinosis, and, rarely, in newborn infants with transient renal failure. The aim of the study was to describe the entity of neonatal transient renal failure with renal medullary hyperechogenicity (NTRFMH). We studied nine term neonates, born between August 1999 and February 2004 in our institution (0.1% of the live born infants), who developed transient renal dysfunction after birth, and in whom renal sonograms showed bilateral medullary hyperechogenicity. Seven of the infants (78%) had anuria until 30-45 hours of age, and two (22%) had oliguria. Peak serum creatinine levels ranged between 0.61 and 1.62 mg/dL (mean: 1.09+/-0.27 mg/dL) at 2-3 days of life. Additional findings included proteinuria in nine infants (100%), uric acid crystalluria in seven (78%), hyperuricemia in four (44%), and hypertension in one (11%). Hyperuricosuria was demonstrated in one out of the seven patients in whom this parameter was determined. Urinary excretion rates of calcium, phosphorus and oxalic acid were normal, as were urinary levels of amino acids and organic acids. Full clinical recovery accompanied by normalization of all laboratory parameters was observed in all infants by 4-6 days of life. Subsequent follow-up showed normal renal function, no urinary abnormalities, and normal renal sonograms in all infants. Our summary of the nine infants with NTRFMH reported on here and a review of 19 cases of this condition reported in the literature reveal a not-so-rare entity of unclear etiology, but excellent prognosis. Physicians caring for neonates should be aware of this benign and transient condition.

Phenotype and Genotype Analysis in Chinese Patients with Gitelman’s Syndrome

Inactivation mutations of the luminal thiazide-sensitive NaCl cotransporter (NCC) in the distal convoluted tubules or the basolateral chloride channel (CLCNKB) in the distal nephron are the most common genetic mutations in Gitelman's syndrome (GS) or Bartter's syndrome (BS). We conducted clinical and molecular studies in Chinese patients with GS or BS. Twenty patients with chronic hypokalemia (15 males and five females, age 25 +/- 7 yr) from 15 unrelated Chinese families were investigated. All had renal K+ wasting, metabolic alkalosis, and normotension. The urinary calcium excretion rate was used to distinguish between BS or GS on clinical grounds. Clinical symptoms and biochemical studies were recorded. Molecular analysis included PCR single-strand confirmational polymorphism, direct sequencing of both the NCC and CLCNKB genes, and restriction fragment length polymorphism. Sixteen patients had a clinical diagnosis of GS with hypocalciuria and four BS without hypocalciuria. Four of these 20 patients did not have hypomagnesemia. The males had severe hypokalemia [1.9 +/- 0.4 mEq/liter (mmol/liter)] with paralytic episodes, whereas females had moderate hypokalemia [2.6 +/- 0.2 mEq/liter (mmol/liter)] and less severe symptoms. There were no mutations detected in CLCNKB. Twelve NCC mutations, including six novel mutations and nine recurrent ones, were identified. Allele frequency of the detected NCC mutations was 3% in 100 healthy subjects. Some GS patients with NCC mutations may have normocalciuria and/or normomagnesemia. Gender differences may account for phenotype variability. Screening of these identified NCC mutations remains the gold standard for the diagnosis of GS.