Nephrolithiasis

Effects of a high-sodium/low-potassium diet on renal calcium, magnesium, and phosphate handling

The distal convoluted tubule (DCT) of the kidney plays an important role in blood pressure regulation by modulating Na⁺ reabsorption via the Na⁺-Cl^- cotransporter (NCC). A diet containing high salt (NaCl) and low K⁺ activates NCC, thereby causing Na⁺ retention and a rise in blood pressure. Since high blood pressure, hypertension, is associated with changes in serum calcium (Ca²⁺) and magnesium (Mg²⁺) levels, we hypothesized that dietary Na⁺ and K⁺ intake affects Ca²⁺ and Mg²⁺ transport in the DCT. Therefore, the present study aimed to investigate the effect of a high-Na⁺/low-K⁺ diet on renal Ca²⁺ and Mg²⁺ handling. Mice were divided in four groups and fed a normal-Na⁺/normal-K⁺, normal-Na⁺/low-K⁺, high-Na⁺/normal-K⁺, or high-Na⁺/low-K⁺ diet for 4 days. Serum and urine were collected for electrolyte and hormone analysis. Gene and protein expression of electrolyte transporters were assessed in kidney and intestine by qPCR and immunoblotting. Whereas Mg²⁺ homeostasis was not affected, the mice had elevated urinary Ca²⁺ and phosphate (P_i) excretion upon high Na⁺ intake, as well as significantly lower serum Ca²⁺ levels in the high-Na⁺/low-K⁺ group. Alterations in the gene and protein expression of players involved in Ca²⁺ and P_i transport indicate that reabsorption in the proximal tubular and TAL is affected, while inducing a compensatory response in the DCT. These effects may contribute to the negative health impact of a high-salt diet, including kidney stone formation, chronic kidney disease, and loss of bone mineral density.

The role of trapped bubbles in kidney stone detection with the color Doppler ultrasound twinkling artifact

The color Doppler ultrasound twinkling artifact, which highlights kidney stones with rapidly changing color, has the potential to improve stone detection; however, its inconsistent appearance has limited its clinical utility. Recently, it was proposed stable crevice bubbles on the kidney stone surface cause twinkling; however, the hypothesis is not fully accepted because the bubbles have not been directly observed. In this paper, the micron or submicron-sized bubbles predicted by the crevice bubble hypothesis are enlarged in kidney stones of five primary compositions by exposure to acoustic rarefaction pulses or hypobaric static pressures in order to simultaneously capture their appearance by high-speed photography and ultrasound imaging. On filming stones that twinkle, consecutive rarefaction pulses from a lithotripter caused some bubbles to reproducibly grow from specific locations on the stone surface, suggesting the presence of pre-existing crevice bubbles. Hyperbaric and hypobaric static pressures were found to modify the twinkling artifact; however, the simple expectation that hyperbaric exposures reduce and hypobaric pressures increase twinkling by shrinking and enlarging bubbles, respectively, largely held for rough-surfaced stones but was inadequate for smoother stones. Twinkling was found to increase or decrease in response to elevated static pressure on smooth stones, perhaps because of the compression of internal voids. These results support the crevice bubble hypothesis of twinkling and suggest the kidney stone crevices that give rise to the twinkling phenomenon may be internal as well as external.

Antiurolithiatic Potential of Neeri against Calcium-Oxalate Stones by Crystallization Inhibition, Free Radicals Scavenging, and NRK-52E Cell Protection from Oxalate Injury

Background

Neeri is a well-established polyherbal formulation prescribed for renal stones by the physicians but has not been experimentally evaluated for its antiurolithiatic potential using cell-lines.

Objective

This study is aimed to scientifically substantiate the antiurolithiatic effect of Neeri extract (NRE) through calcium oxalate (CaOx) crystallization inhibition, scavenging of free radicals, and protection of renal tubular epithelial NRK-52E cells from oxalate-induced injury.

Materials and Methods

The crystallization inhibition was studied by turbidimetric assay while the free radical scavenging potential was determined for superoxide and nitric oxide (NO) radicals. The cytoprotective effect against oxalate-induced injury was assessed by estimating lactate dehydrogenase (LDH) leakage and determining cell viability using 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay.

Results

NRE significantly inhibited the CaOx crystallization in a concentration-dependent manner and also scavenged superoxide (IC₅₀ 302.88 μg/ml) and NO (IC₅₀ 300.45 μg/ml) free radicals. It did not show any significant cytotoxicity for NRK-52E cells till the highest dose (500 μg/ml) and found to be safe. When NRK-52E cells, injured by exposing to oxalate crystals for 24 h, were treated with NRE, it appreciably prevented the cell injury in a dose-dependent manner. It significantly decreased the elevated LDH leakage toward normal range and improved renal cell viability (82.37% ± 0.87%), hence, prevented growth and retention of crystals.

Conclusion

The experimental findings concluded that Neeri is a potent antiurolithiatic formulation that inhibited CaOx crystallization and prevented tubular retention of crystals by protecting the renal cells against oxalate-induced injury as well as reducing the oxidative stress by scavenging free radicals.

SUMMARY

Neeri extract significantly (P < 0.001) inhibited the in vitro crystallization (88.11% ± 7.70%) of calcium oxalateIt reduced oxidative stress by scavenging superoxide and nitric oxide free radicalsIt significantly (P < 0.001) improved the cell viability by inhibiting the leakage of lactate dehydrogenase in a dose-dependent manner. Abbreviations used: A_c: Absorbance of control, A_t: Absorbance of test, ANOVA: Analysis of variance, CaOx: Calcium oxalate, DMEM: Dulbecco's Modified Eagle's Medium, DMSO: Dimethyl sulfoxide, EDTA: Ethylenediaminetetraacetic acid, FBS: Fetal bovine serum, INT: Iodonitrotetrazolium, LDH: Lactate dehydrogenase, M: Molar, ml: Milliliter, mM: Millimolar, MTT: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, NAD: Nicotinamide adenine dinucleotide, NADPH: Nicotinamide adenine dinucleotide phosphate, NBT: Nitro blue tetrazolium, nm: Nanometer, NO: Nitric oxide, NRE: Neeri extract, PMS: Phenazine methosulfate, ROS: Reactive oxygen species, S_c: Slope of the graph of control, SEM: Standard error of mean, S_i: Slope of the graph with inhibitor, U/I: International unit, mg: Microgram, ml: Microliter.

Determining normal values of urinary phosphorus excretion in 3913 healthy children aged 2-18 to aid early diagnosis and treatment for urolithiasis

AIM

This study determined the specific reference values for urinary phosphorus excretion in healthy children and adolescents aged 2-18 years and evaluated whether they changed with age during growth and were gender dependent.

METHODS

We enrolled 3913 healthy children and adolescents aged 2-18 years to this study. The study population was divided into age groups, and the analysis was performed in one-year periods, separately for boys and girls. Urinary phosphorus excretion was analysed using four categories: P1 in mmol/24 hour units, P2 in mmol/kg/24 hours, P3 in mmol/1.73 m² /24 hours and P4 in mmol/mmol creatinine.

RESULTS

Clear differences in urinary exertion for girls and boys were observed as well as systematic changes with age. The boys presented with significantly higher daily urinary phosphorus excretion independent of its manner of expression (p < 0.001). The median urinary phosphorus (P1) rose with age (p < 0.001). Percentile tables of phosphorous exertion are presented.

CONCLUSION

This was the largest study of urinary phosphate excretion based on a randomly selected sample of girls and boys aged 2-18 years. It highlights the importance of determining phosphorus reference values for children of different ages to provide early diagnosis and treatment for urolithiasis.

Systematic evaluation for effects of urine pH on calcium oxalate crystallization, crystal-cell adhesion and internalization into renal tubular cells

Urine pH has been thought to be an important factor that can modulate kidney stone formation. Nevertheless, there was no systematic evaluation of such pH effect. Our present study thus addressed effects of differential urine pH (4.0–8.0) on calcium oxalate (CaOx) crystallization, crystal-cell adhesion, crystal internalization into renal tubular cells, and binding of apical membrane proteins to the crystals. Microscopic examination revealed that CaOx monohydrate (COM), the pathogenic form, was crystallized with greatest size, number and total mass at pH 4.0 and least crystallized at pH 8.0, whereas COD was crystallized with the vice versa order. Fourier-transform infrared (FT-IR) spectroscopy confirmed such morphological study. Crystal-cell adhesion assay showed the greatest degree of crystal-cell adhesion at the most acidic pH and least at the most basic pH. Crystal internalization assay using fluorescein isothiocyanate (FITC)-labelled crystals and flow cytometry demonstrated that crystal internalization into renal tubular cells was maximal at the neutral pH (7.0). Finally, there were no significant differences in binding capacity of the crystals to apical membrane proteins at different pH. We concluded that the acidic urine pH may promote CaOx kidney stone formation, whereas the basic urine pH (i.e. by alkalinization) may help to prevent CaOx kidney stone disease.

Response of Npt2a knockout mice to dietary calcium and phosphorus

Mutations in the renal sodium-dependent phosphate co-transporters NPT2a and NPT2c have been reported in patients with renal stone disease and nephrocalcinosis, but the relative contribution of genotype, dietary calcium and phosphate to the formation of renal mineral deposits is unclear. We previously reported that renal calcium phosphate deposits persist and/or reappear in older Npt2a-/- mice supplemented with phosphate despite resolution of hypercalciuria while no deposits are seen in wild-type (WT) mice on the same diet. Addition of calcium to their diets further increased calcium phosphate deposits in Npt2a-/-, but not WT mice. The response of PTH to dietary phosphate of Npt2a-/- was blunted when compared to WT mice and the response of the urinary calcium x phosphorus product to the addition of calcium and phosphate to the diet of Npt2a-/- was increased. These finding suggests that Npt2a-/- mice respond differently to dietary phosphate when compared to WT mice. Further evaluation in the Npt2a-/- cohort on different diets suggests that urinary calcium excretion, plasma phosphate and FGF23 levels appear to be positively correlated to renal mineral deposit formation while urine phosphate levels and the urine anion gap, an indirect measure of ammonia excretion, appear to be inversely correlated. Our observations in Npt2a-/- mice, if confirmed in humans, may be relevant for the optimization of existing and the development of novel therapies to prevent nephrolithiasis and nephrocalcinosis in human carriers of NPT2a and NPT2c mutations.

Epidemiology of stone disease across the world

Nephrolithiasis is a highly prevalent disease worldwide with rates ranging from 7 to 13% in North America, 5-9% in Europe, and 1-5% in Asia. Due to high rates of new and recurrent stones, management of stones is expensive and the disease has a high level of acute and chronic morbidity. The goal of this study is to review the epidemiology of stone disease in order to improve patient care. A review of the literature was conducted through a search on Pubmed^®, Medline^®, and Google Scholar^®. This review was presented and peer-reviewed at the 3rd International Consultation on Stone Disease during the 2014 Société Internationale d'Urologie Congress in Glasgow. It represents an update of the 2008 consensus document based on expert opinion of the most relevant studies. There has been a rising incidence in stone disease throughout the world with a narrowing of the gender gap. Increased stone prevalence has been attributed to population growth and increases in obesity and diabetes. General dietary recommendations of increased fluid, decreased salt, and moderate intake of protein have not changed. However, specific recommended values have either changed or are more frequently reported. Geography and environment influenced the likelihood of stone disease and more information is needed regarding stone disease in a large portion of the world including Asia and Africa. Randomized controlled studies are lacking but are necessary to improve recommendations regarding diet and fluid intake. Understanding the impact of associated conditions that are rapidly increasing will improve the prevention of stone disease.

Some Work on the Diagnosis and Management of Kidney Stones with Ultrasound

Ultrasound is currently the only noninvasive technology able to completely diagnose and manage kidney stones.

Providing Access to Care through a 24-Hour Dedicated Stone Line

INTRODUCTION

Many patients with urolithiasis are seen acutely in the emergency department for initial treatment. In an effort to improve cost and quality of care increasing focus has been placed on shifting management of low acuity conditions from emergency departments to outpatient settings. One barrier to such initiatives is timely access to outpatient services. We established a telephone stone line to provide access to outpatient urological care of kidney stones and we report our initial experience.

METHODS

A 24-hour dedicated telephone stone line was created with calls answered by dedicated staff. A computer program was created to track stone line calls and post-call care. We retrospectively analyzed all stone line calls received in a 4-year period with the focus on utilization and cost. An e-mail survey was performed to assess patient satisfaction.

RESULTS

Between January 2009 and July 2013 the mean call volume was 2,107 per year. A significant distribution of calls was seen across all days and hours. Duration was less than 15 minutes in 7,761 calls (82%). Patients or family members placed 77% of calls and physicians placed 16%. As a result of a stone line call, 4,173 patients (76%) were seen by a urologist within 48 hours. Of the patients 88% reported satisfaction with the stone line. The mean annual cost of providing the telephone stone line was $51,873.

CONCLUSIONS

Our experience demonstrates sustained utilization of and satisfaction with the telephone stone line. Further, stone line use results in timely outpatient evaluation in the majority of patients. Further analysis to assess for a cost benefit is ongoing.

Gut microbiota and oxalate homeostasis

This perspective focuses on how the gut microbiota can impact urinary oxalate excretion in the context of hyperoxaluria, a major risk factor in kidney stone disease. In the genetic disease of Primary Hyperoxaluria Type 1 (PH1), an increased endogenous production of oxalate, due to a deficiency of the liver enzyme alanine-glyoxylate aminotransferase (AGT), results in hyperoxaluria and oxalate kidney stones. The constant elevation in urinary oxalate in PH1 patients ultimately leads to tissue deposition of oxalate, renal failure and death and the only known cure for PH1 is a liver or liver-kidney transplant. The potential impact of a probiotic/therapeutic approach may be clinically significant in PH1 and could also extend to a much larger population of idiopathic oxalate stone formers who comprise ~12% of Americans, individuals with enteric hyperoxaluria, and an emerging population of hyperoxaluric patients who have undergone bariatric surgery and develop kidney stone disease as a consequence.

The Capabilities and Limitations of Clinical Magnetic Resonance Imaging for Detecting Kidney Stones: A Retrospective Study

The purpose of this work was to investigate the performance of currently available magnetic resonance imaging (MRI) for detecting kidney stones, compared to computed tomography (CT) results, and to determine the characteristics of successfully detected stones. Patients who had undergone both abdominal/pelvic CT and MRI exams within 30 days were studied. The images were reviewed by two expert radiologists blinded to the patients' respective radiological diagnoses. The study consisted of four steps: (1) reviewing the MRI images and determining whether any kidney stone(s) are identified; (2) reviewing the corresponding CT images and confirming whether kidney stones are identified; (3) reviewing the MRI images a second time, armed with the information from the corresponding CT, noting whether any kidney stones are positively identified that were previously missed; (4) for all stones MRI-confirmed on previous steps, the radiologist experts being asked to answer whether in retrospect, with knowledge of size and location on corresponding CT, these stones would be affirmed as confidently identified on MRI or not. In this best-case scenario involving knowledge of stones and their locations on concurrent CT, radiologist experts detected 19% of kidney stones on MRI, with stone size being a major factor for stone identification.

Motion artifacts in kidney stone imaging using single-source and dual-source dual-energy CT scanners: a phantom study

PURPOSE

Dual-energy computed tomography (DECT) has shown the capability of differentiating uric acid (UA) from non-UA stones with 90-100% accuracy. With the invention of dual-source (DS) scanners, both low- and high-energy images are acquired simultaneously. However, DECT can also be performed by sequential acquisition of both images on single-source (SS) scanners. The objective of this study is to investigate the effects of motion artifacts on stone classification using both SS-DECT and DS-DECT.

METHODS

114 kidney stones of different types and sizes were imaged on both DS-DECT and SS-DECT scanners with tube voltages of 80 and 140 kVp with and without induced motion. Postprocessing was conducted to create material-specific images from corresponding low- and high-energy images. The dual-energy ratio (DER) and stone material were determined and compared among different scans.

RESULTS

For the motionless scans, all stones were correctly classified with SS-DECT, while two cystine stones were misclassified with DS-DECT. When motion was induced, 94% of the stones were misclassified with SS-DECT versus 11% with DS-DECT (P < 0.0001). Stone size was not a factor in stone misclassification under motion. Stone type was not a factor in stone misclassification under motion with SS-DECT, although with DS-DECT, cystine showed higher number of stone misclassification.

CONCLUSIONS

Motion artifacts could result in stone misclassification in DECT. This effect is more pronounced in SS-DECT versus DS-DECT, especially if stones of different types lie in close proximity to each other. Further, possible misinterpretation of the number of stones (i.e., missing one, or thinking that there are two) in DS-DECT could be a potentially significant problem.

Idiopathic hypercalciuria and formation of calcium renal stones

The most common presentation of nephrolithiasis is idiopathic calcium stones in patients without systemic disease. Most stones are primarily composed of calcium oxalate and form on a base of interstitial apatite deposits, known as Randall's plaque. By contrast some stones are composed largely of calcium phosphate, as either hydroxyapatite or brushite (calcium monohydrogen phosphate), and are usually accompanied by deposits of calcium phosphate in the Bellini ducts. These deposits result in local tissue damage and might serve as a site of mineral overgrowth. Stone formation is driven by supersaturation of urine with calcium oxalate and brushite. The level of supersaturation is related to fluid intake as well as to the levels of urinary citrate and calcium. Risk of stone formation is increased when urine citrate excretion is <400 mg per day, and treatment with potassium citrate has been used to prevent stones. Urine calcium levels >200 mg per day also increase stone risk and often result in negative calcium balance. Reduced renal calcium reabsorption has a role in idiopathic hypercalciuria. Low sodium diets and thiazide-type diuretics lower urine calcium levels and potentially reduce the risk of stone recurrence and bone disease.

YouTubeTM as a source of patient information for ureteroscopy

Objective:

YouTubeTM has provided a platform that is utilised by millions. Patients are increasingly utilising this source of information. We set out to systematically analyse the quality of ureteroscopy videos.

Materials and methods:

YouTubeTM was searched using the term ‘ureteroscopy’. Content was assessed using the British Association of Urological Surgeons website criteria. Information relating to management options, procedural description, stent insertion, recovery and complications was rated. An overall rating was given. Videos were also analysed in terms of country of origin, view count, likes, dislikes, source and technical quality. The kappa statistic was used.

Results:

A total of 59 videos were analysed. The total number of viewings was 557,896 (range: 42– 121,943), with an average number of 9456 viewings per video. The information content was either poor or average in 98% ( n = 58) of videos, with only 2% ( n=1) rated as good and 0% achieving an excellent rating. Technical quality was rated as poor in 28 videos, average in 22 and good in nine videos. Most videos were broadcast by surgeons or surgical institutes (48/59).

Conclusion:

The quality of videos is variable. Patients should not be encouraged to use this for education. Opportunity has arisen for the endourology community to produce high quality video broadcasts to optimise patient understanding.

Diuretic and antiurolithiatic activities of an ethanolic extract of Acorus calamus L. rhizome in experimental animal models

Acorus calamus is a plant commonly used as a traditional herbal medicine and possesses the wide range of pharmacological applications. The present study investigated the diuretic and antiurolithiatic activities of an ethanolic extract of Acorus calamus L. (Family: Araceae) rhizome (EEAC). For diuretic activity, three doses of EEAC (250, 500 and 750 mg/kg) were studied, and measurement of the urinary volume and electrolytes (Na⁺ and K⁺) concentration were taken as evaluation parameters. On the other hand, ethylene glycol induced urolithiasis (0.75% v/v in drinking water for 28 days) was used to study the antiurolithiatic effect of EEAC at the oral dose of 750 mg/kg in male Wistar albino rats. CYSTONE (750 mg/kg, p.o.) was used as a standard reference drug in the present study. After completion of the 28-days respective treatments, the level of various urolithiatic promoters in the biological samples (urine, serum and kidney homogenate) and renal function were used as criteria for assessing the antiurolithiatic effect of EEAC. Results indicate that, the EEAC (750 mg/kg, p.o.) produced significant increase in urine volume (p < 0.001) and urinary excretion of Na⁺ and K⁺ electrolytes (p < 0.05) in a pattern comparable to that of furosemide. In ethylene glycol induced urolithiatic model, EEAC significantly (p < 0.05) decreased excretion and deposition of various urolithiatic promoters as compared to urolithiatic control in a pattern comparable to that of CYSTONE. The EEAC supplementation also prevents the impairment of renal functions. The antiurolithiatic mechanism is mediated possibly through diuretic and nephroprotective actions of the active compounds of rhizomes.

The use of alpha-1 adrenergic blockers in children with distal ureterolithiasis: a systematic review and meta-analysis

INTRODUCTION

Urinary lithiasis is the main urologic cause of emergency treatment in adult patient. In the past years, the incidence in children population has increased. However, literature about the use of alpha-1 adrenergic blockers in pediatric population with distal ureterolithiasis is still scarce. The drug acts by decreasing ureter contractions, especially in the distal portion, facilitating calculus expulsion.

OBJECTIVE

This review has the objective to evaluate the use of alpha-1 adrenergic blockers as medical expulsive treatment in children with distal ureterolithiasis.

EVIDENCE ACQUISITION

An electronic literature search was performed using the MEDLINE, COCHRANE, and LILACS databases. We further searched manually the references of the primary studies. Searches were concluded on October 4th, 2014. Articles were selected, independently and in pairs, by the respective titles and summaries. Any divergence was resolved by consensus.

EVIDENCE SYNTHESIS

Alpha-1 adrenergic antagonists increased the probability of calculus expulsion by 27% (NNT=4). Calculi smaller than 5mm, increased by 33% (NNT=3). Larger than 5mm, increased by 34% (NNT=3).

CONCLUSION

Alpha-1 adrenergic blocker use is related with a greater incidence of expulsion of ureteral calculi, smaller or greater than 5mm, and fewer episodes of pain when compared to ibuprofen. However it is necessary larger samples to enhance the power analysis of the expulsion of ureteral calculi larger than 5mm and the episodes of pain.

PATIENT SUMMARY

This review analyzed the outcome of alpha adrenergic antagonist in children with ureteral calculi. We conclude that it is the best medicine for use, since it helps the expulsion of the stone.

Nutritional Management of Kidney Stones (Nephrolithiasis)

The incidence of kidney stones is common in the United States and treatments for them are very costly. This review article provides information about epidemiology, mechanism, diagnosis, and pathophysiology of kidney stone formation, and methods for the evaluation of stone risks for new and follow-up patients. Adequate evaluation and management can prevent recurrence of stones. Kidney stone prevention should be individualized in both its medical and dietary management, keeping in mind the specific risks involved for each type of stones. Recognition of these risk factors and development of long-term management strategies for dealing with them are the most effective ways to prevent recurrence of kidney stones.

Vascular Calcification and Stone Disease: A New Look towards the Mechanism

Calcium phosphate (CaP) crystals are formed in pathological calcification as well as during stone formation. Although there are several theories as to how these crystals can develop through the combined interactions of biochemical and biophysical factors, the exact mechanism of such mineralization is largely unknown. Based on the published scientific literature, we found that common factors can link the initial stages of stone formation and calcification in anatomically distal tissues and organs. For example, changes to the spatiotemporal conditions of the fluid flow in tubular structures may provide initial condition(s) for CaP crystal generation needed for stone formation. Additionally, recent evidence has provided a meaningful association between the active participation of proteins and transcription factors found in the bone forming (ossification) mechanism that are also involved in the early stages of kidney stone formation and arterial calcification. Our review will focus on three topics of discussion (physiological influences-calcium and phosphate concentration-and similarities to ossification, or bone formation) that may elucidate some commonality in the mechanisms of stone formation and calcification, and pave the way towards opening new avenues for further research.

Calcium ions promote primary renal epithelial cell differentiation into cells with bone-associated phenotypes via transforming growth factor-β1-induced epithelial-mesenchymal transition in idiopathic hypercalciuria patients

The present study aimed to identify the characteristics and cross‑talk between transforming growth factor β1 (TGF‑β1) and calcium ions in nephrolithiasis patients with idiopathic hypercalciuria (IH) in order to elucidate the potential mechanisms underlying changes in cell phenotype induced by bone‑associated factors and their influence on renal nephrolithiasis formation. Blood samples from a total of 29 nephrolithiasis patients with IH, 29 renal stone patients without IH and 29 healthy age‑matched normal controls were subjected to quantification of peripheral serum TGF‑β1, osteopontin (OPN) and bone morphogenetic protein 2 (BMP2) using ELISA. This was followed by detection of BMP2, OPN and 1,25‑dihydroxyvitamin D3 receptor (VDR) mRNA and protein levels in primary renal epithelial cells (PRECs) of IH and HK‑2 human proximal tubular cell lines (control) using reverse transcription quantitative polymerase chain reaction (RT‑qPCR) and western blot analyses. The mRNA expression levels of BMP2, OPN and VDR in PRECs and HK‑2 were evaluated following stimulation with various concentrations of TGF‑β1 (0.5, 2.0 and 5.0 ng/ml), Ca2+ (0.5, 1.5 and 2.5 mM) or TGF‑β1 and Ca2+ combined using RT‑qPCR, respectively. TGF‑β1, BMP2 and OPN expression levels in patients with IH were all significantly higher than those in the control group. The mRNA and protein expression levels of BMP2 and VDR were significantly higher in PRECs than those in HK‑2 cells. Following incubation with TGF‑β1 and/or Ca2+, the mRNA expression levels of BMP2, OPN and VDR in PRECs increased in a dose‑dependent manner; however, no significant differences were observed in HK‑2 cells with increasing TGF‑β1 dosage. Co‑incubation with TGF‑β1 and Ca2+ in PRECs and HK‑2 cell lines resulted in similar effects and the expression of BMP2, OPN and VDR mRNA increased in a time‑dependent manner. In conclusion, the results of the present study demonstrated that TGF‑β1 regulated the expression of BMP2, OPN and VDR in PRECs, but not in HK‑2 cells. Co‑incubation with TGF‑β1 and Ca2+ significantly increased the expression levels of bone‑associated factors in PRECs and HK‑2 cells, which suggested that this process may be partially responsible for the pathogenesis of calcium stone development, and also associated with bone formation and the TGF‑β1‑induced epithelial to mesenchymal transition.

Renal and blood pressure effects from environmental cadmium exposure in Thai children

Very few studies have shown renal and blood pressure effects from environmental cadmium exposure in children. This population study examined associations between urinary cadmium excretion, a good biomarker of long-term cadmium exposure, and renal dysfunctions and blood pressure in environmentally exposed Thai children. Renal functions including urinary excretion of β2-microglobulin, calcium (early renal effects), and total protein (late renal effect), and blood pressure were measured in 594 primary school children. Of the children studied, 19.0% had urinary cadmium ≥ 1 μg/g creatinine. The prevalence of urinary cadmium ≥ 1 μg/g creatinine was significantly higher in girls and in those consuming rice grown in cadmium-contaminated areas. The geometric mean levels of urinary β2-microglobulin, calcium, and total protein significantly increased with increasing tertiles of urinary cadmium. The analysis did not show increased blood pressure with increasing tertiles of urinary cadmium. After adjusting for age, sex, and blood lead levels, the analysis showed significant positive associations between urinary cadmium and urinary β2-microglobulin and urinary calcium, but not urinary total protein nor blood pressure. Our findings provide evidence that environmental cadmium exposure can affect renal functions in children. A follow-up study is essential to assess the clinical significance and progress of renal effects in these children.

Adequate dietary intake and nutritional status in patients with nephrolithiasis: new targets and objectives

OBJECTIVES

Modifiable risk factors for kidney stones, such as diet and nutritional status, are targets in the treatment and prevention of nephrolithiasis. The aim of the present study was to assess the nutritional state and energy and nutrient adequacy of patients with nephrolithiasis via anthropometric evaluation, dietary inquiry, and urine biochemistry.

DESIGN

The present observational cross-sectional study.

SETTING

An outpatient, nephrolithiasis clinic of a tertiary care, university hospital.

SUBJECTS

A total of 31 patients with nephrolithiasis and 25 controls were assessed.

INTERVENTIONS

All patients were subjected to nutritional evaluation, including dietary inquiry and chemical tests of blood and 24-hour urine samples.

MAIN OUTCOME MEASURE

Nutritional state and nutrient ingestion adequacy.

RESULTS

The group of patients with nephrolithiasis exhibited high body mass index, abdominal circumference, and body fat percentage values. The protein, sodium, calcium, potassium, and oxalate intakes differed significantly from the recommended values in both the nephrolithiasis and control groups. The nephrolithiasis and control groups differed only in terms of oxalate intake (159 ± 119.27 vs. 112 ± 47.9, respectively, P = .042). Regarding urine biochemistry, 30% of the patients with nephrolithiasis exhibited hypercalciuria, versus 12% of the control group.

CONCLUSIONS

The prevalence of individuals with overweight/obesity was high in both the nephrolithiasis and control groups. This finding indicates that in addition to orientation regarding nonlithogenic dietary habits, continuous education by a multidisciplinary staff must also address the prevention and treatment of obesity.

Does crystal deposition in genetic hypercalciuric rat kidney tissue share similarities with bone formation?

OBJECTIVE

To address the effect of bone-related factors and 1,25(OH)2D3/vitamin D receptor (VDR) on renal stone formation in idiopathic hypercalciuria using genetic hypercalciuric rats.

METHODS

The basal levels of bone-related factors were detected in Sprague-Dawley and genetic hypercalciuric rats. In VDR silenced kidneys, the expression levels of bone morphogenetic protein 2 (BMP2), runt-related transcription factor 2 (Runx2), Osterix, and osteopontin (OPN) were measured, respectively. Tubular calcium phosphate deposits in kidneys and renal tubular epithelial cells (RTECs) were assessed using von Kossa stain. Kidneys were stained with immunohistochemical staining for OPN expression. Gene and protein expression levels of BMP2, Runx2, and Osterix were examined in RTECs incubated with 1,25(OH)2D3.

RESULTS

The basal levels of BMP2, Runx2, Osterix, and OPN were significantly increased in genetic hypercalciuric rats, whereas there were no differences in the expression levels of msh homeobox homolog 2 and alkaline phosphatase between the genetic hypercalciuric and normal control rats. VDR knockdown in genetic hypercalciuric rats reduced the expression levels of BMP2, Runx2, Osterix, and OPN. Tubular calcium phosphate deposits were also decreased in VDR silenced kidneys. Immunohistochemical staining showed that there was a reduction in OPN expression in RTECs along with reduction in calcification. Gene and protein expression levels of BMP2, Runx2, and Osterix were upregulated in RTECs incubated with 1,25(OH)2D3. The calcium phosphate deposits in RTECs were also increased by elevated 1,25(OH)2D3.

CONCLUSION

Our findings indicate that BMP2, Runx2, Osterix, and OPN might play an important role in renal stone formation in idiopathic hypercalciuria, and 1,25(OH)2D3/VDR might be the significant regulator in this process.

An association between kidney stone composition and urinary metabolic disturbances in children

OBJECTIVE

To determine kidney stone composition in children and to correlate stone fractions with urinary pH and metabolic urinary risk factors.

PATIENTS AND METHODS

We studied 135 pediatric patients with upper urinary tract lithiasis in whom excreted or extracted stones were available for analyses. Composition of stones was analyzed. A 24-hour urine assessment included volume, pH and daily excretions of calcium, oxalate, uric acid, cystine, creatinine, phosphate, magnesium and citrate.

RESULTS

Calcium oxalate was the major component of 73% stones, followed by struvite (13%) and calcium phosphate (9%). Uric acid was present in almost half of stones, but in rudimentary amounts. The calcium oxalate content in calculi showed a strong relationship with calciuria, and moderate association with oxaluria, magnesuria and acidification of urine. The percent content of struvite presented reverse and lower correlations with regard to the above parameters. Calcium phosphate stone proportion had low associations with urinary risk factors.

CONCLUSIONS

Calciuria, oxaluria, magnesuria and low urine pH exerted the biggest influence on calcium oxalate content in pediatric renal stones. Relationships of urinary risk factors with calculi calcium phosphate content were of unclear significance. Urinary citrate excretion did not significantly correlate with kidney stone composition in children.

Three-dimensional dual-energy computed tomography for enhancing stone/stent contrasting and stone visualization in urolithiasis

The use of dual-energy computed tomography (DECT) for evaluating urinary calculi has been appreciated due to the modality's capability of differentiating between uric acid (UA) and non-UA stones, which are color coded based on a postprocessing algorithm. No other imaging modality or laboratory test is able to identify the stone composition without first attaining the stone material. Knowledge of the stone composition is clinically significant since UA calculi may be treated medically whereas non-UA calculi may require surgical removal. Regardless of the stone type, ureteral stents are often placed to prevent or treat obstruction. Recent work has demonstrated that commonly used stents are also colored based on their dual energy characteristics and may thereby either improve or obscure the identification of adjacent calculi. Herein, we report the case of a 65-year-old man who underwent percutaneous nephrolithotomy of a large staghorn stone with subsequent significant residual stone fragments noted on a follow-up scan. By using three-dimensional DECT and taking advantage of color contrasting, the stone composition, burden, shape, and boundary were clearly depicted apart from the adjacent stent, resulting in successful medical treatment and obviating the need for further surgical intervention.

Kidney stones: an update on current pharmacological management and future directions

INTRODUCTION

Kidney stones are a common problem worldwide with substantial morbidities and economic costs. Medical therapy reduces stone recurrence significantly. Much progress has been made in the last several decades in improving therapy of stone disease.

AREAS COVERED

This review discusses i) the effect of medical expulsive therapy on spontaneous stone passage, ii) pharmacotherapy in the prevention of stone recurrence and iii) future directions in the treatment of kidney stone disease.

EXPERT OPINION

Fluid intake to promote urine volume of at least 2.5 L each day is essential to prevent stone formation. Dietary recommendations should be adjusted based on individual metabolic abnormalities. Properly dosed thiazide treatment is the standard therapy for calcium stone formers with idiopathic hypercalciuria. Potassium alkali therapy is considered for hypocitraturia, but caution should be taken to prevent potential risk of calcium phosphate stone formation. For absorptive hyperoxaluria, low oxalate diet and increased dietary calcium intake are recommended. Pyridoxine has been shown effective in some cases of primary hyperoxaluria type I. Allopurinol is used in calcium oxalate stone formers with hyperuricosuria. Treatment of cystine stones remains challenging. Tiopronin can be used if urinary alkalinization and adequate fluid intake are insufficient. For struvite stones, complete surgical removal coupled with appropriate antibiotic therapy is necessary.

Randomized controlled trial of febuxostat versus allopurinol or placebo in individuals with higher urinary uric acid excretion and calcium stones

BACKGROUND AND OBJECTIVES

Higher urinary uric acid excretion is a suspected risk factor for calcium oxalate stone formation. Febuxostat, a xanthine oxidoreductase inhibitor, is effective in lowering serum urate concentration and urinary uric acid excretion in healthy volunteers and people with gout. This work studied whether febuxostat, compared with allopurinol and placebo, would reduce 24-hour urinary uric acid excretion and prevent stone growth or new stone formation.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In this 6-month, double-blind, multicenter, randomized controlled trial, hyperuricosuric participants with a recent history of calcium stones and one or more radio-opaque calcium stone ≥ 3 mm (as seen by multidetector computed tomography) received daily febuxostat at 80 mg, allopurinol at 300 mg, or placebo. The primary end point was percent change from baseline to month 6 in 24-hour urinary uric acid. Secondary end points included percent change from baseline to month 6 in size of index stone and change from baseline in the mean number of stones and 24-hour creatinine clearance.

RESULTS

Of 99 enrolled participants, 86 participants completed the study. Febuxostat led to significantly greater reduction in 24-hour urinary uric acid (-58.6%) than either allopurinol (-36.4%; P=0.003) or placebo (-12.7%; P<0.001). Percent change from baseline in the size of the largest calcium stone was not different with febuxostat compared with allopurinol or placebo. There was no change in stone size, stone number, or renal function. No new safety concerns were noted for either drug.

CONCLUSIONS

Febuxostat (80 mg) lowered 24-hour urinary uric acid significantly more than allopurinol (300 mg) in stone formers with higher urinary uric acid excretion after 6 months of treatment. There was no change in stone size or number over the 6-month period.

Ramadan fasting and patients with renal diseases: A mini review of the literature

Fasting during the month of Ramadan is one of the five pillars of Islam. During this month, adult Muslims are obligated to refrain from eating and drinking from dawn to dusk. Although based on Islamic principles patients are exempted from fasting, each year, many Muslim patients express their willingness to observe the fast in Ramadan month to respect the cultural customs. There are concerns about the impact of fluid restriction and dehydration during Ramadan fasting for patients with renal diseases. In this study, we reviewed the PubMed, Google Scholar, EBSCO, SCIRUS, Embase, and DOAJ data sources to identify the published studies on the impact of Ramadan fasting on patients with renal diseases. Our review on published reports on renal transplant recipients revealed no injurious effect of Ramadan fasting for the renal graft function. Nearly all studies on this topic suggest that Ramadan fasting is safe when the function of the renal graft is acceptable and stable. Regarding the impact of Ramadan fasting on patients with chronic kidney disease, there is concern about the role of renal hypoperfusion in developing tubular cell injury. Finally, there is controversy between studies about the risk of dehydration in Ramadan in developing renal stones. There are uncertainties about the change in the incidence of renal colic in Ramadan month compared with the other periods of the year. Despite such discrepancies, nearly all studies are in agreement on consuming adequate amounts of water from dusk to dawn to reduce the risk of renal stone formation.

Preventive effect of specific antioxidant on oxidative renal cell injury associated with renal crystal formation

OBJECTIVE

To investigate whether calcium oxalate monohydrate (COM), a key element of hyperoxaluria, would induce renal cell injury through oxidative stress and also whether certain antioxidants could prevent chemically induced renal crystal formation in rats.

MATERIALS AND METHODS

COM-exerted oxidative stress on the kidney epithelial Madin-Darby canine kidney cells was assessed using the lipid peroxidation assay. Glyoxalase I (Gly-I) activity was also determined. Two antioxidants, vitamin C and N-acetylcysteine (NAC), were then tested to determine whether they could abolish such oxidative stress in Madin-Darby canine kidney cells. Both antioxidants were also tested to determine whether they might prevent or reduce renal crystal formation induced with ethylene glycol (EG) and vitamin D3 (VD3) in Wistar rats.

RESULTS

COM (200 μg/mL) demonstrated ∼1.3-fold greater oxidative stress with a significant reduction in cell viability and Gly-I activity compared with controls. However, such adverse events were almost completely prevented with NAC but not with vitamin C. In the animal study, no renal crystals were seen in the sham group. However, numerous crystals, with reduced Gly-I activity and elevated oxidative stress, were found in the EG-VD3 group. However, markedly (>70%) fewer crystals, with full Gly-I activity and diminished oxidative stress, were detected in the EG-VD3+NAC group.

CONCLUSION

COM exerted oxidative stress on Madin-Darby canine kidney cells, leading to cell viability reduction and Gly-I inactivation, with NAC fully preventing such adverse consequences. Similarly, numerous crystals with Gly-I inactivation and elevated oxidative stress seen in the rats (EG-VD3) were also significantly prevented with NAC supplement. Thus, NAC might have clinical implications in preventing oxidative renal cell injury and, ultimately, kidney stone formation.

Inhibition of calcium oxalate crystallisation in vitro by an extract of Bergenia ciliata

OBJECTIVE

To evaluate the effectiveness of an extract obtained from the rhizomes of Bergenia ciliata (Saxifragaceae) on the inhibition of calcium oxalate (CaOx) crystallisation in vitro.

MATERIALS AND METHODS

A hydro-alcoholic extract (30:70, v/v) of rhizomes of B. ciliata was prepared at different concentrations (1-10 mg/mL). The crystallisation of CaOx monohydrate (COM) was induced in a synthetic urine system. The nucleation and aggregation of COM crystals were measured using spectrophotometric methods. The rates of nucleation and aggregation were evaluated by comparing the slope of the turbidity of a control system with that of one exposed to the extract. The results were compared with a parallel study conducted with a marketed poly-herbal combination, Cystone, under identical concentrations. Crystals generated in the urine were also analysed by light microscopy. Statistical differences and percentage inhibitions were calculated and assessed.

RESULTS

The extract of B. ciliata was significantly more effective in inhibiting the nucleation and aggregation of COM crystals in a dose-dependent manner than was Cystone. Moreover, the extract induced more CaOx dihydrate crystals, with a significant reduction in the number and size of COM crystals.

CONCLUSION

An extract of the traditional herb B. ciliata has an excellent inhibitory activity on crystalluria and therefore might be beneficial in dissolving urinary stones. However, further study in animal models of urolithiasis is needed to evaluate its potential anti-urolithiatic activity.

Metabolic evaluation in patients with nephrolithiasis: A report from Isfahan, Iran

Background:

Nephrolithiasis is a major public health problem worldwide. In recent years, growing evidence suggest that this disease may originate from underlying metabolic disorders. This is the first study that reports the frequency of different metabolic abnormalities among patients with nephrolithiasis in Isfahan, a large central province of Iran.

Materials and Methods:

From the time period between March 2009 and August 2010, 437 nephrolithiasis patients in Isfahan province enrolled in this study. Metabolic evaluation was performed by obtaining a 24-hours urine sample and fasting venous blood draw. We analyzed urine samples for volume, creatinine, calcium, citrate, oxalate, uric acid, sodium, and cystine. Fasting blood samples were assessed for serum calcium, phosphorus, sodium, potassium, uric acid, albumin, creatinine and blood urea nitrogen.

Results:

The mean age was 46 ± 13.8 years (rang: 18-87). Nearly 50% were first time stone formers. The most common metabolic abnormalities were hypocitraturia (40.5%) and hypernatriuria (31.8%) that was followed by hyperoxaluria (28.8%). Hypercalciuria was detected only in 9.2% of the cases.

Conclusion:

Although, high calcium excretion was the most frequent metabolic derangement in several similar studies, in our province with considerably high prevalence of vitamin D deficiency, it is not frequent among nephrolithiasis patients. Instead, other metabolic risk factors were in higher frequencies.

Cigarette smoking and nephrolitiasis in adult individuals

Background

Nephrolithiasis is a widespread multifactorial disorder. Constitutional, environmental and genetic factors play a role in stone formation. Although important advances have been made in understanding the pathophysiology of stone formation, none of the many theories have given a satisfactory explanation of this process.

Objectives

The objective of study was to evaluate the probable relationship between cigarette smoking and nephrolitiasis in adult men.

Patients and Methods

A total of 102 cases diagnosed with nepholithiasis and 121 age-matched healthy controls were recruited from June 2010 to September 2011. Smoking status and resultant data was obtained from both groups.

Results

Twenty seven (26.5%) of the patients with stones and eighteen (14.9%) of the control group were current cigarette smokers. Our findings showed that smoking significantly increases the risk of nepholithiasis (OR = 2.06, 95% CI: 1.06-4.01, P = 0.034). There was no significant difference in the number of cigarettes smoked (P = 0.830) and years of smoking (P = 0.536) between subjects with and without stones (P = 0.536).

Conclusions

This study suggests that cigarette smoking might be an independent risk factor for the development of nephrolithiasis.

Association of elevated urinary cadmium with urinary stone, hypercalciuria and renal tubular dysfunction in the population of cadmium-contaminated area

Excessive urinary calcium is the major risk of renal tubular dysfunction and urinary stone formation. We examined the association of elevated urinary cadmium with urinary stones and chronic kidney disease (CKD) in 1,085 study residents of 13 cadmium-contaminated villages. Elevated urinary cadmium was significantly correlated with urinary stone and CKD. Elevated urinary cadmium appeared to increase risk of urinary stone and CKD; ORs and 95 % CIs were 2.73 (1.16, 6.42) and 3.73 (2.50, 5.57) after adjusting for other co-variables. This study revealed that elevated urinary stone and CKD induced by cadmium might increase the risk of urinary stone and CKD.

Engineering of polarized tubular structures in a microfluidic device to study calcium phosphate stone formation

This communication describes the formation of tubular structures with a circular cross-section by growing epithelial cells in a microfluidic (MF) device. Here we show for the first time that it is possible to form a monolayer of polarized cells, embedded within the MF device which can function as an in vivo epithelia. We showed: i) the overexpression of specific protein(s) of interest (i.e., ion channel and transport proteins) is feasible inside tubular structures in MFs; ii) the functional kinetic information of Ca(2+) in cells can be measured by microflurometry using cell permeable Ca(2+) probe under confocal microscope; and iii) calcium phosphate stones can be produced in real time in MFs with Ca(2+) transporting epithelia. These data suggest that tubular structures inside this MF platform can be used as a suitable model to understand the molecular and pharmacological basis of calcium phosphate stone formation in the epithelial or other similar cellular micro environments.

Urinary metabolic phenotyping the slc26a6 (chloride-oxalate exchanger) null mouse model

The prevalence of renal stone disease is increasing, although it remains higher in men than in women when matched for age. While still somewhat controversial, several studies have reported an association between renal stone disease and hypertension, but this may be confounded by a shared link with obesity. However, independent of obesity, hyperoxaluria has been shown to be associated with hypertension in stone-formers, and the most common type of renal stone is composed of calcium oxalate. The chloride-oxalate exchanger slc26a6 (also known as CFEX or PAT-1), located in the renal proximal tubule, was originally thought to have an important role in sodium homeostasis and thereby blood pressure control, but it has recently been shown to have a key function in oxalate balance by mediating oxalate secretion in the gut. We have applied two orthogonal analytical platforms (NMR spectroscopy and capillary electrophoresis with UV detection) in parallel to characterize the urinary metabolic signatures related to the loss of the renal chloride-oxalate exchanger in slc26a6 null mice. Clear metabolic differentiation between the urinary profiles of the slc26a6 null and the wild type mice were observed using both methods, with the combination of NMR and CE-UV providing extensive coverage of the urinary metabolome. Key discriminating metabolites included oxalate, m-hydroxyphenylpropionylsulfate (m-HPPS), trimethylamine-N-oxide, glycolate and scyllo-inositol (higher in slc26a6 null mice) and hippurate, taurine, trimethylamine, and citrate (lower in slc26a6 null mice). In addition to the reduced efficiency of anion transport, several of these metabolites (hippurate, m-HPPS, methylamines) reflect alteration in gut microbial cometabolic activities. Gender-related metabotypes were also observed in both wild type and slc26a6 null groups. Urinary metabolites that showed a sex-specific pattern included trimethylamine, trimethylamine-N-oxide, citrate, spermidine, guanidinoacetate, and 2-oxoisocaproate. The gender-dependent metabolic expression of the consequences of slc26a6 deletion might have relevance to the difference in prevalence of renal stone formation in men and women. The different composition of microbial metabolites in the slc26a6 null mice is consistent with the fact that the slc26a6 transporter is found in a range of tissues, including the kidney and intestine, and provides further evidence for the "long reach" of the microbiota in physiological and pathological processes.

Total and soluble oxalate content of some Indian spices

Spices, such as cinnamon, cloves, cardamom, garlic, ginger, cumin, coriander and turmeric are used all over the world as flavouring and colouring ingredients in Indian foods. Previous studies have shown that spices contain variable amounts of total oxalates but there are few reports of soluble oxalate contents. In this study, the total, soluble and insoluble oxalate contents of ten different spices commonly used in Indian cuisine were measured. Total oxalate content ranged from 194 (nutmeg) to 4,014 (green cardamom) mg/100 g DM, while the soluble oxalate contents ranged from 41 (nutmeg) to 3,977 (green cardamom) mg/100 g DM. Overall, the percentage of soluble oxalate content of the spices ranged from 4.7 to 99.1% of the total oxalate content which suggests that some spices present no risk to people liable to kidney stone formation, while other spices can supply significant amounts of soluble oxalates and therefore should be used in moderation.

Influence of overweight on 24-hour urine chemistry studies and recurrent urolithiasis in children

Purpose

We investigated the influence of overweight on 24-hour urine chemistry studies and recurrent urolithiasis (UL) in children.

Materials and Methods

A retrospective cohort study was designed to assess children who presented with UL at a pediatric institution between 1985 and 2010. We calculated body mass index percentile (BMIp) adjusted for gender and age according to the 2007 Korean Children and Adolescents Growth Chart and stratified the children into 3 BMI categories: lower body weight (LBW, BMIp≤10), normal BW (NBW, 10<BMIp<85), and upper BW (UBW, BMIp≥85). Twenty-four hour urine chemistry studies (urine volume, creatinine, calcium, oxalate, citrate, and pH) were compared between the 3 BMIp groups. Univariate and multivariate analyses were performed to assess independent risk factors for stone recurrence.

Results

A total of 125 patients were included. The age of the patients in the NBW group was older than that of patients in the LBW group, but 24-hour urine chemistry studies did not differ significantly between the three groups. Mean urine citrate levels were lower (0.273±0.218 mg/mg/d vs. 0.429±0.299 mg/mg/d, p<0.05) and the incidence of hypocitraturia was higher (81.5% vs. 45.7%, p<0.05)) in the recurrent stone former group. In the univariate analysis, hypocitraturia and acidic urinary pH were risk factors, but in the multivariate analysis, only hypocitraturia was a risk factor for stone recurrence (hazard ratio, 3.647; 95% confidence interval, 1.047 to 12.703). In the Kaplan-Meier curve, the hypocitraturia group showed higher recurrence than did the normocitraturia group (p<0.05).

Conclusions

Unlike in adults, in children, overweight adjusted for gender and age was not associated with 24-hour urine chemistry studies and was not a risk factor for recurrent UL. Hypocitraturia was the only risk factor for UL in children.

Urine risk factors in children with calcium kidney stones and their siblings

Calcium nephrolithiasis in children is increasing in prevalence and tends to be recurrent. Although children have a lower incidence of nephrolithiasis than adults, its etiology in children is less well understood; hence, treatments targeted for adults may not be optimal in children. To better understand metabolic abnormalities in stone-forming children, we compared chemical measurements and the crystallization properties of 24-h urine collections from 129 stone formers matched to 105 non-stone-forming siblings and 183 normal, healthy children with no family history of stones, all aged 6 to 17 years. The principal risk factor for calcium stone formation was hypercalciuria. Stone formers have strikingly higher calcium excretion along with high supersaturation for calcium oxalate and calcium phosphate, and a reduced distance between the upper limit of metastability and supersaturation for calcium phosphate, indicating increased risk of calcium phosphate crystallization. Other differences in urine chemistry that exist between adult stone formers and normal individuals such as hyperoxaluria, hypocitraturia, abnormal urine pH, and low urine volume were not found in these children. Hence, hypercalciuria and a reduction in the gap between calcium phosphate upper limit of metastability and supersaturation are crucial determinants of stone risk. This highlights the importance of managing hypercalciuria in children with calcium stones.

Development of a method for the quantitative analysis of urinary stones, formed by a mixture of two components, using infrared spectroscopy

OBJECTIVES

The analysis of urinary stones is used for the diagnosis of the etiology of an episode of nephrolithiasis. The technique considered as standard for this purpose is infrared spectroscopy (IR). However, when the urinary stone is formed by a mixture of components, only semi-quantitative information can be achieved using IR. The objective of this work is the development of a quantitative method.

DESIGN AND METHODS

Bands in the IR spectra of several mixtures were studied, in order to design a calibration model useful to determine the quantitative composition of the urinary stones. For mixtures of two components, four mathematical models were proposed. To assess the validity of these models, nine series of mixtures of two components were prepared, using the most frequently compounds found in urinary stones, for analyzing by ATR-FTIR spectroscopy (Attenuated Total Reflection Fourier Transformed Infrared).

RESULTS

Nine series of nine mixtures of two components were prepared for this work. The IR spectrum was recorded for each mixture and the absorbance intensities at selected wave numbers were used to apply the proposed mathematical models. There were good linear correlations between the analytical signals (IR absorbances) and the analytical responses (weight fractions) using the calibration lines. The validity of the method was checked by the comparison between the weight fractions resulted from the calibration lines and the real weight fractions obtained by weighing, presenting good correlation parameters.

CONCLUSIONS

The method developed in this work has been useful for the quantification of compounds which are commonly found in urinary stones. This method allows a total characterization of the urinary stones (qualitative and quantitative) by means of IR spectroscopy.