Evaluation and treatment of pediatric idiopathic urolithiasis-revisited

Should pediatric idiopathic hypercalciuria be treated with hypocalciuric agents?

BACKGROUND

Hypercalciuria is the most common metabolic risk factor for calcium urolithiasis and is associated with bone loss in adult patients. Reduced bone mineral density (BMD) was already described in idiopathic hypercalciuria (IH) children, but the precise mechanisms of bone loss or inadequate bone mass gain remain unknown. Life-long hypercalciuria might be considered a risk to change bone structure and determine low bone mass throughout life. The peak of bone mass should occur without interferences. A beneficial effect of citrate formulations and thiazides on bone mass in adult and pediatric patients with IH have been shown.

AIM

To evaluate whether pharmacological therapy has a beneficial effect on bone mass in children and adolescents with IH.

METHODS

This retrospective cohort study evaluated 40 hypercalciuric children non-responsive to lifestyle and diet changes. After a 2-mo run-in period of citrate formulation (Kcitrate) usage, the first bone densitometry (DXA) was ordered. In patients with sustained hypercalciuria, a thiazide diuretic was prescribed. The second DXA was performed after 12 mo. Bone densitometry was performed by DXA at lumbar spine (L2-L4). A 24-h urine (calcium, citrate, creatinine) and blood samples (urea, creatinine, uric acid, calcium, phosphorus, magnesium, chloride, hemoglobin) were obtained. Clinical data included age, gender, weight, height and body mass index.

RESULTS

Forty IH children; median age 10.5 year and median time follow-up 6.0 year were evaluated. Nine patients were treated with Kcitrate (G1) and 31 with Kcitrate + thiazide (G2). There were no differences in age, gender, body mass index z-score and biochemical parameters between G1 and G2. There were no increases in total cholesterol, kalemia and magnesemia. Calciuria decreased in both groups after treatment. Lumbar spine BMD z-score increased after thiazide treatment in G2. There was no improvement in G1.

CONCLUSION

Results point to a beneficial effect of thiazide on lumbar spine BMD z-score in children with IH. Further studies are necessary to confirm the results of the present study.

Evolution of bone mineral density in patients with idiopathic hypercalciuria: a 20-year longitudinal study

BACKGROUND

Several recent studies reported bone mineral density (BMD) reduction in pediatric patients with idiopathic hypercalciuria (IH). This longitudinal study aimed to evaluate BMD evolution in IH patients through three bone densitometry studies conducted over 20 years on average. A second objective was to evaluate urine calcium and citrate excretion during this period.

METHODS

Case notes of 34 patients diagnosed with IH at age 7.9 ± 3, alongside results of two bone densitometry studies, performed at 10.5 ± 2.7 (BMD1) and 14.5 ± 2.7 (BMD2) years of age, were reviewed. Patients underwent a third densitometry study in adulthood (BMD3) aged 28.3 ± 2.9. Mean follow-up duration (time-lapse between BMD1 and BMD3) was 17.7 ± 1.4 years.

RESULTS

Statistically significant differences were found between z-BMD3 (- 0.85 ± 1.10) and z-BMD1 (- 1.47 ± 0.99) (P = 0.001) as well as between z-BMD3 and z-BMD2 (- 1.33 ± 1.20) (P = 0.016). At the end of follow-up, z-BMD3 was superior to z-BMD2 in 23 adult patients (67.6%) and lower in 11 patients (5M, 6F; 32.3%). Both men and women showed increased bone mass over time, although such increases were significant only for women. The gradual decrease observed in calcium/creatinine and citrate/creatinine ratios could be related to improvement in osteoblastic activity and especially reduction in osteoclastic activity.

CONCLUSIONS

In patients with IH, BMD improves, which may be related especially to female sex, increment of body mass, and reduction in bone resorption. Upon reaching adulthood, urine calcium and citrate excretion tend to decrease so lithogenic risk still remains. The cause of the latter is unknown, although it likely relates to changes in bone activity.

The interest of oral calcium loads test in the diagnosis and management of pediatric nephrolithiasis with hypercalciuria: Experience from a tertiary pediatric centre

INTRODUCTION

The use of calcium load has been forgotten in pediatrics until recently whereas it is of utmost importance to have a practical approach to guide management of hypercalciuric nephrolithiasis.

OBJECTIVE

The purpose of this study was to evaluate the practical interest of oral calcium loads to improve the overall management of nephrolithiasis in children.

METHODS

We retrospectively studied all pediatric patients having undergone an oral calcium load in our pediatric nephrology unit between September 2015 and April 2017.

RESULTS

A total of 16 patients were included, at a median age of 12.0 (5.5-17.5) years. The indications of oral calcium load were: presence of an active urolithiasis without any obvious explanation after ruling out the "classical" biological abnormalities, or presence of hypercalciuria with stones composed of weddellite or carbapatite crystals. Among the 16 patients, 6 (38%) patients displayed absorptive hypercalciuria, 2 (12%) renal leak, 3 (19%) "unclassified" inadapted PTH, and 5 (31%) a normal calcium load test. The result of oral calcium load modified the clinical management in 14 (88%) patients, mainly based on the type of hypercalciuria. It allowed us to individualize nutritional advice: in patients with absorptive hypercalciuria, we proposed calcium intake within the lower normal range for age with dairy products not enriched with vitamin D, with the advice to avoid salt and calcium loads during evenings. Conversely, in patients with resorptive hypercalciuria, we proposed normal calcium intake for age. Showing the results of the calcium load is meaningful to patients and parents, and can be considered as an "educational" tool.

DISCUSSION

To the best of our knowledge, this study is the first to evaluate the interest of calcium load in children with nephrolithiasis in an era of routine PTH and 1-25-D assessment. Here, we demonstrate the feasibility and safety of oral calcium load in children, its interest to understand the underlying mechanisms of hypercalciuria, and its major interest as an "educational tool" for patients to explain them the underlying mechanisms and thus guide the therapeutic management using an individualized dietary approach. This study did not include many patients, but to the best of our knowledge, this is the first study evaluating and validating the feasibility of a safe and non-expensive diagnosis tool in pediatric hypercalciuria.

CONCLUSION

Oral calcium load is helpful to guide therapeutic adaptation in pediatrics using an individualized dietary approach.

Inherited conditions resulting in nephrolithiasis

PURPOSE OF REVIEW

Prevalence of pediatric urolithiasis is increasing, which is definitively visible in increasing numbers of presentations in emergency or outpatient clinics. In pediatric patients, a genetic or metabolic disease has to be excluded, so that adequate treatment can be installed as early as possible. Only then either recurrent stone events and chronic or even end-stage kidney disease can be prevented.

RECENT FINDINGS

The genetic background of mostly monogenic kidney stone diseases was unravelled recently. In hypercalcuria, for example, the commonly used definition of idiopathic hypercalciuria was adopted to the genetic background, here three autosomal recessive hereditary forms of CYP24A1, SLC34A1 and SLC34A3 associated nephrocalcinosis/urolithiasis with elevated 1.25-dihydroxy-vitamin D3 (1.25-dihydroxy-vitamin D3) (calcitriol) levels. In addition either activating or inactivating mutations of the calcium-sensing receptor gene lead either to hypocalcemic hypercalciuria or hypercalcemic hypocalciuria. In primary hyperoxaluria, a third gene defect was unravelled explaining most of the so far unclassified patients. In addition, these findings lead to new treatment options, which are currently evaluated in phase III studies.

SUMMARY

Kidney stones are not the disease itself, but only its first symptom. The underlying disease has to be diagnosed in every pediatric patient with the first stone event.

Genetische Nierensteinerkrankungen

Die Inzidenz und Prävalenz von Steinerkrankungen haben in den letzten Jahren deutlich zugenommen. Es ist von entscheidender Bedeutung, möglichst frühzeitig eine richtige Diagnose der zugrunde liegenden Erkrankung zu stellen, um die richtige Therapie einzuleiten und damit möglicherweise schwerwiegende Folgen, wie terminales Nierenversagen, zu verhindern. Bei Kindern lassen sich in ca. 75 % der Fälle genetische oder anatomische Ursachen identifizieren. Die verschiedenen zugrunde liegenden Erkrankungen für die jeweiligen lithogenen Risikofaktoren werden hier präsentiert und die entsprechenden Therapieoptionen, sofern vorhanden, erläutert.

Does idiopathic hypercalciuria affect bone metabolism during childhood? A prospective case-control study

BACKGROUND

A limited number of studies have evaluated biochemical bone metabolism markers in children with idiopathic hypercalciuria, which in adults has been linked with osteopenia. Our aim was to investigate in children with idiopathic hypercalciuria biochemical markers of bone formation and resorption and the osteoprotegerin (OPG) and soluble receptor activator of nuclear factor kB ligand (sRANKL) system which is involved in the osteoclastogenesis process.

METHODS

A prospective study was conducted on 50 children with idiopathic hypercalciuria and 50 healthy age-, sex-, and Tanner stage-matched control subjects. Following the diagnosis, patients were requested to follow a 3-month dietary recommendation for idiopathic hypercalciuria. In patients, at diagnosis and at 3 months of follow-up, and in controls, bone-related hormones and serum/urine biochemical parameters were studied. The bone formation markers (total ALP and osteocalcin) and the bone resorption markers (β-Crosslaps) and the OPG and sRANKL levels were determined.

RESULTS

No differences were found in the bone formation markers or OPG and sRANKL between the children with idiopathic hypercalciuria and controls. The β-Crosslaps and the β-Crosslaps/osteocalcin ratio were higher in the patients at diagnosis than in controls (p = 0.019 and p = 0.029, respectively), with a trend to decrease after the 3-month dietary intervention. The initially increased 24-h urinary Ca in the patients decreased after the 3-month dietary intervention (p = 0.002).

CONCLUSIONS

Children with idiopathic hypercalciuria had biochemical markers compatible with normal bone formation but increased bone resorption. After a 3-month dietary intervention, the trend observed towards decrease in the serum β-Crosslaps may reflect a beneficial response.

Kidney Stone Composition in Third-World Areas: What Kashgar Tells Us?

OBJECTIVE

To analyze urinary stone compositions in patients from Kashgar, China.

MATERIALS AND METHODS

We analyzed the components of urinary stones in 732 consecutive patients with urolithiasis admitted to the First and Second People's Hospital of Kashgar Prefecture, Xinjiang, from July 2014 to November 2016. The patients were divided into two groups by ages: group A, 0 to 18 years and group B, >18 years old. The distributions of various stone compositions were analyzed and correlated with the gender and age.

RESULTS

The mean age of group A was 3.90 ± 4.09 years and that of group B was 39.88 ± 16.40 years. The overall gender ratio (male:female) was 2.27:1. Ammonium acid urate (AAU) stone was the most frequent stone, male 35.83% and female 33.48%. Female patients were significantly more common than male patients in calcium apatite stone (p = 0.004). Of all 732 cases, patients younger than 18 years were more than patients older than 18 years (58.47% vs 41.53%). The majority of the patients (77.87%) had the stone located in the upper urinary tract. Two peak ages for both genders were noted in 1 to 3 years and 19 to 40 years group of the patients. In group of 1 to 3 years patients, male were more than female (37.60% vs 24.55%, p = 0.001), whereas in the group of 10 to 18 years patients, female were more than male (10.71% vs 4.13%). AAU was the predominant stone component in group <1 year (70. 5%, p < 0.01, as compared with other groups.). Uric acid stone was more prevalent in group >60 years (66.8%, p < 0.01) than in other groups. Patients in 1 to 3 years were in the peak age group of AAU stones in both the upper and lower urinary tract.

CONCLUSION

Most of the patients with urolithiasis diagnosed and treated in Kashgar are <18 years old, especially younger than 3 years old. The most frequent stone component in this area was AAU. More than 50% patients <18 years old had AAU stone. The mechanisms that could trigger the high prevalence of AAU stone in patients <18 years old are worth further investigation.

Role of FGF23 in Pediatric Hypercalciuria

Background

This study explored the possible role of FGF23 in pediatric hypercalciuria.

Methods

Plasma FGF23 was measured in 29 controls and 58 children and adolescents with hypercalciuria: 24 before treatment (Pre-Treated) and 34 after 6 months of treatment (Treated). Hypercalciuric patients also measured serum PTH hormone, 25(OH)vitD, phosphate, calcium, creatinine, and 24 h urine calcium, phosphate, and creatinine.

Results

There were no differences in age, gender, ethnicity, or body mass index either between controls and patients, or between Pre-Treated and Treated patients. Median plasma FGF23 in controls was 72 compared with all patients, 58 RU/mL (p = 0.0019). However, whereas FGF23 in Pre-Treated patients, 73 RU/mL, was not different from controls, in Treated patients it was 50 RU/mL, significantly lower than in both controls (p < 0.0001) and Pre-Treated patients (p = 0.02). In all patients, there was a correlation between FGF23 and urinary calcium (r = 0.325; p = 0.0014). Treated patients had significantly lower urinary calcium (p < 0.0001), higher TP/GFR (p < 0.001), and higher serum phosphate (p = 0.007) versus Pre-Treated patients.

Conclusions

Pharmacological treatment of hypercalciuric patients resulted in significantly lower urinary calcium excretion, lower serum FGF23, and elevated TP/GFR and serum phosphate concentration, without significant changes in PTH. Further studies are indicated. This trial is registered with Clinical Registration Number RBR 8W27X5.

24 Hour urine metabolic differences between solitary and multiple stone formers: Results of the Collaboration on Urolithiasis in Pediatrics (CUP) working group

INTRODUCTION

Specific factors associated with the risk of developing pediatric urinary stone disease remain unclear, especially those that may be associated with recurrent stone disease.

OBJECTIVE

We compared the results of 24-h urine collections in children with a solitary stone episode to those with multiple stone episodes to determine if there is a difference that may be associated with multiple stone formation in children.

STUDY DESIGN

A multi-institutional retrospective analysis was completed to assess 24-h urinary metabolic profiles in children with urolithiasis aged 2-18 years old. Differences in mean urine collections between the two groups were assessed using chi-square tests to test the associations among gender, stone type, and multiple stone status, as well as multivariate analyses using general linear models.

RESULTS

We analyzed 142 solitary stone patients and 136 multiple stone patients from four centers were included. Multiple stone patients were older than solitary stone patients (mean 13.4 ± 3.6 years vs. 12 ± 3.9 years, p = 0.002). Females were more likely to have multiple stones (58% vs. 39%, p = 0.002). BMI was not associated with multiple stones (p = 0.8467). Multiple stone formers had lower urine volumes, although this did not reach statistical significance when compared with solitary stone formation (20.4 mL/kg/day ± 11.5 vs. 22.9 ± 13.0, p = 0.0880). Higher values for super-saturation of calcium oxalate were associated with multiple stone disease in univariate (p = 0.0485) and multivariate analysis (p = 0.0469) (Figure). Centers located in the Southeast of the United States saw a higher proportion of children with multiple stones (Tennessee 62.7%, Virginia 44.4%, Oregon 31.6%, Michigan 27.3%, p < 0.0001).

DISCUSSION

In a large multi-institutional retrospective analysis we found that multiple stone disease was associated with higher super-saturations of calcium oxalate. Many urinary parameters changed with patient age, highlighting that the values should be interpreted with respect to patient age. The inability to comment on follow-up because of the nature of our dataset is a limitation of this study.

CONCLUSION

Multiple stone disease in children is associated with higher super-saturation calcium oxalate, while lower urinary volume may also be associated with multiple stones; however, further study is required. Early metabolic evaluation may help risk stratify children likely to form multiple stones.

Urinary stone disease in pediatric and adult metabolic bone clinic patients

Kidney stones are increasing in the pediatric and adult populations; similarly osteoporosis is increasingly recognized in children. While kidney stone formers are known to suffer from low bone density, metabolic bone patients have not been considered a high risk population for kidney stones. Retrospective chart review of Nationwide Children's Hospital Metabolic Bone Clinic patients from October 2009-2013. Patients were identified by ICD 9 codes for osteoporosis, osteopenia, low bone density and kidney stones. Only patients with radiologic evidence of both diseases were included.Twenty-six of 889 patients met criteria; this is equivalent to an incidence of 30 per 100,000 patients. Osteoporosis was the most frequent bone diagnosis. Males were the majority (68%). Most common secondary diagnoses: seizure (52%) and cerebral palsy (44%).

TREATMENT

calcium (48%), vitamin D (40%), bisphosphonates (48%). The majority (75%) were non-ambulatory. Most frequent lithogenic medications: Topiramate (42%) and corticosteroids (27%). This is one of the first studies to consider metabolic bone patients as high risk for urinary stone disease. We found a higher rate of kidney stones in pediatric metabolic bone patients compared to data available for the general pediatric kidney stone population. The most common risk factor for bone and stone disease was nonambulatory status. Males were more frequently affected than females; this is the reverse of general adolescent kidney stone population. The predominance of cerebral palsy and seizure patients can be attributed to their frequency of non-ambulatory status and lithogenic medications such as Topiramate.

Ureteroscopy for treatment of upper urinary tract stones in children: technical considerations

The incidence of pediatric urolithiasis is increasing. While many smaller stones may pass spontaneously, surgical therapy is sometimes warranted. Surgical options include shock wave lithotripsy, ureteroscopy, percutaneous nephrolithotomy, and open surgery. Ureteroscopy represents a minimally invasive approach, and it is increasingly being used to treat pediatric upper tract calculi. Ureteroscopy is performed under anesthesia and fluoroscopic guidance, with basket extraction or lithotripsy of the calculi. Technical considerations include active or passive ureteral dilatation, the use of ureteral access sheaths for larger stone burdens, and post-operative stent placement. The current pediatric literature suggests high success rates (equal to or surpassing shock wave lithotripsy) and low complication rates. However, concerns remain regarding feasibility in patients with variant anatomies and risk due to intra-operative radiation exposure.

Underuse of 24-hour urine collection among children with incident urinary stones: a quality-of-care concern?

OBJECTIVE

To determine the prevalence of 24-hour urine collection among first-time pediatric stone formers and investigate factors associated with its use.

MATERIALS AND METHODS

Using data from the MarketScan Commercial Claims and Encounters Database (2002-2006), children presenting to the emergency department with an incident episode of upper urinary tract stone disease were identified through a diagnosis code-based algorithm. The number of patients performing a 24-hour urine collection within 6 months of this encounter was calculated. Temporal trends in the prevalence of use were assessed. We fitted multivariate logistic regression models to examine factors associated with testing.

RESULTS

In total, 1848 children presented with an incident upper tract stone, of which 12.0% submitted a 24-hour urine collection. This percentage remained stable over the study period. Testing was more common among younger patients (P <.001) and those who visited urologists (P <.001) or nephrologists (P <.001). The odds of testing were nearly 4-fold or 7-fold higher if the patient saw a urologist (odds ratio, 3.99; 95% confidence interval, 2.83-5.62) or a nephrologist (odds ratio, 7.00; 95% confidence interval, 3.95-12.41), respectively.

CONCLUSION

Despite rates of stone recurrence, 24-hour urine collection appears to be underused among children. Efforts to increase its use are therefore likely to benefit pediatric patients with urinary stone disease.

American and Brazilian Children With Primary Urolithiasis: Similarities and Disparities

Objectives. Considering the differences in location, socioeconomic background, and cultural background, the aim of this study was to try to identify possible factors associated with the increased incidence of urolithiasis by comparing American and Brazilian children with stones. Methods. Data of 222 American and 190 Brazilian children with urolithiasis were reviewed including age, gender, body mass index, imaging technique used (ultrasound and computed tomography), and 24-hour urine volume and chemistries. Results. There were no differences between age and gender at diagnosis. Brazilian children were leaner but in no population did obesity rate exceed that of the general population. Ultrasound was most commonly used to diagnose stones, even more so in Brazilians. Decreased urine flow was more common among Americans (P = .004), hypercalciuria among Brazilians (P = .001), and elevated Ca/citrate ratio among Americans (P = .009). There were no differences between the groups in the frequency of hypocitraturia, hyperuricosuria, absorptive hyperoxaluria, and cystinuria. Conclusions. Despite some differences between the populations, the leading causes of urolithiasis among both were “oliguria,” hypercalciuria, and high Ca/citrate ratio. In neither country was obesity the reason for the increase in incidence of urolithiasis, nor was the use of computed tomography. The similarities between the 2 populations call for combining efforts in addressing the leading causes of pediatric urolithiasis.

Correlation of the body mass index and calcium nephrolithiasis in adult population

Introduction:

Prevalence of the kidney stones (renal calculi) increase in several countries in parallel with the increase of overweight, diabetes (type 2 diabetes) and hypertension.

Goal:

The goal of our research was to evaluate the connection between the calcium nephrolithiasis and overweight, as quantified using the Body Mass Index (BMI) of the adult population, with a particular reflection on the age groups within it.

Material and methods:

The research was prospective and it was implemented at the Clinical Center of Banja Luka, at the Urology Clinic in the period from 1^st April 2012 to 1^st January 2013. The trial encompassed 120 patients with calcium nephrolithiasis of the upper part of the urinary tract and 120 patients without nephrolithiasis. A group of patients with the calcium nephrolithiasis presented a working group, while a group of patients without nephrolithiasis presented a control group. The BMI obtained on the basis of bodily weight and height of the patient, where the age and sex of specific reference values of the BMI were developed by the Center for Disease Control and Prevention (CDC) were not used in the calculation of the BMI.

Results:

Analyzing the values of the BMI in relation to age groups, where there was a statistically significant difference in the working group, whereas in the control group there was a statistically high significant difference, testing of statistical significance of the average value of the BMI was done by observed age groups of working and control group, as well as to the total sample of work and control group using the Chi-Square test and T-test for independent samples. Having observed the age group of 20-40 years, statistically significant differences have been noted at the level of risk of 10%, which confirms that there is a connection between the categories of the BMI and the group, which the patient comes from (Chi-Square test p-0.05), that is, T-test has shown that the values are different at the level of 10%, i.e. p<0.1 (p=0.073). Having observed the age group 40-60, there was no dependency between the category of the BMI and the group, that is, the differences are not statistically significant, p>0.05 (t-test p=0.314). In addition to this, the average BMI values are not significantly different, p>0.05 (t-test p=0.871). Having observed the age group of the older than 60, there was no dependency between the category of the BMI and the group, that is, the differences are not statistically significant, p>0.05 (Chi-square test p=0.167). Having observed the total sample of the working and control group, there was no dependency of the category of the BMI and the group (or urolithiasis), p>0.05 (Chi-Square test p=1.208), whereas the results of the T-test showed that there was no statistically significant difference of the arithmetic mean values of the BMI working group and control group, p>0.05 (t-test p=0.620).

Conclusion:

Overweight in younger age groups of adult population may be connected to the occurrence of calcium nephrolithiasis, thus we suggest that urolithiasis should be considered with them, as part of overweight, by which a change of living habits and the manner of food consumption could prevent this disease.

Clinical importance of renal calyceal microlithiasis in children

BACKGROUND

Renal calyceal microlithiasis refers to a hyperechogenic spot in renal calyces <3 mm in diameter detected on renal sonography. These spots possibly represent the first step in calculus formation. The aim of this study was to analyze the clinical presentation, predisposing factors, prognosis and clinical importance of these hyperechogenic spots in renal calyces, renal calyceal microlithiasis, during childhood.

METHODS

The data of 292 children (135 girls, 157 boys) with microlithiasis diagnosed between January 1998 and December 2010 were evaluated retrospectively. Demographic data, serum biochemistry, urinary metabolic factors, and renal sonography results were obtained from patient files. A total of 228 patients were re-evaluated at least 6 months after the first observation of renal calyceal microlithiasis and at 6-12 month intervals thereafter.

RESULTS

Mean age was 16.8 ± 14.9 months, and mean follow-up duration was 14.6 ± 5.9 months. Presenting symptoms were abdominal or flank pain (41.1%), hematuria (35.6%), dysuria (24.7%) and urinary tract infection (34.6%). Previous ultrasounds were normal in 35% of the children. Metabolic and anatomic abnormalities were found in 55.5% and 17.8%, respectively. Hypercalciuria was the most common metabolic abnormality (88.9%). Among 228 patients who had been re-evaluated, microlithiasis disappeared in 37.7%; decreased in number or size in 23.7%; progressed to renal stone formation in 10.6%; increased in number of microlithiasis in 19.0%; and remained unchanged on radiology in 9.0%.

CONCLUSION

Renal calyceal microlithiasis represents a spectrum of clinical situations and underlying metabolic abnormalities that need further investigation in children.

Pediatric urolithiasis: experience from a tertiary referral center

OBJECTIVE

Pediatric urolithiasis can cause significant morbidity and damage to the kidney, or even renal failure. We review our experience of the management of urolithiasis in pediatric patients at a tertiary referral center.

PATIENTS AND METHODS

We reviewed medical records of all children with urolithiasis who were diagnosed and managed at our center from August 2003 to October 2011. Management was planned according to stone burden and location. We noted and statistically analysed data about age, sex, stone burden, clinical features, management, metabolic abnormalities and recurrence.

RESULTS

There were 325 children with 378 stone sites. Age range was 3-17 (mean 8) years. The male to female ratio was 3:1. Most common presentation was abdominal pain in 257 children (79%), and the most common stone site was kidney in 215 (57%). Twenty-four (7%) children (stone burden ≤3 mm) were managed conservatively, while the rest received some form of intervention. Metabolic workup could be done in 154 (47%) children. A metabolic abnormality was seen in 67 (43%) children, normocalcemic hypercalciuria being the most common. Recurrence of urolithiasis was seen in 78 (24%) children after a mean follow-up of 3.2 (1-6) years, and was more common in those who had a metabolic abnormality or in whom small residual fragments were left in situ.

CONCLUSIONS

Availability of smaller instruments has led to safer use of percutaneous endoscopy and ureteroscopy in children, with results comparable to those in adults and an acceptable complication rate. The presence of a metabolic abnormality is quite common and is a cause of recurrence.

[Urolithiasis in childhood]

Urinary stone disease is relatively rare in children with an overall incidence of 1-2 %; however, it is often associated with metabolic abnormalities that may lead to recurrent stone formation. Stone analysis and subsequent metabolic evaluation is therefore mandatory for this high-risk group after the first stone event. The objectives of stone management in children should be complete stone clearance, prevention of stone recurrence, preservation of renal function, control of urinary tract infections, correction of anatomical abnormalities and correction of the underlying metabolic disorders. The full range of minimally invasive procedures is available if active stone removal is necessary. The majority of stones in children can be managed either with extracorporeal shock wave lithotripsy which has a higher efficacy in children than in adults, percutaneous nephrolithotomy, ureterorenoscopy or a combination of these modalities while open or laparoscopic surgery is limited to well-selected cases with underlying anatomical abnormalities.

Pediatric primary urolithiasis: 12-year experience at a Midwestern Children's Hospital

PURPOSE

Due to environmental and social changes (and possibly obesity) as new risk factors for stone formation in adults and changes in imaging techniques, we assessed whether etiologies of primary pediatric urolithiasis have changed, and if relationships exist between the condition and obesity or imaging technique.

MATERIALS AND METHODS

All pediatric patients with documented primary urolithiasis who underwent serum and 24-hour urine analyses between 1999 and 2010 were evaluated. Age at diagnosis, gender, body mass index and imaging technique were recorded.

RESULTS

Of the 222 patients (48% male) all had normal serum creatinine, electrolytes and minerals. Primary pediatric urolithiasis was diagnosed by ultrasound in 73% of cases and computerized tomography in 27%. Mean ± SD annual incidence of urolithiasis per 1,000 clinic visits increased from 2.4 ± 1.5 in the first half of the study period to 6.2 ± 2.1 in the second half (p <0.005). Mean ± SD age at diagnosis was 11.8 ± 3.8 years and body mass index was 21.7 ± 5.7 (rate of overweight 15%). A total of 140 patients had urine output less than 1.0 ml/kg per hour, with this being the only abnormality in 54. Hypercalciuria was observed in 46% of patients, hypocitraturia in 10% and high calcium-to-citrate ratio in 51%. Mild absorptive hyperoxaluria was noted in 3 patients and hyperuricosuria in 11, with all 14 exhibiting at least 1 additional abnormality. Cystinuria was present in 1 patient. No etiology was identified in 20 patients (9.0%).

CONCLUSIONS

Oliguria and hypercalciuria continue to be the most common etiologies of pediatric primary urolithiasis, followed by hypocitraturia. The recent increase in stone incidence is unlikely due to increased use of computerized tomography. Incidence of obesity was not higher than in the general population. Hyperoxaluria and cystinuria are rare, and thus might not be indicated in the initial analysis.

Bone disease in pediatric idiopathic hypercalciuria

Idiopathic hypercalciuria (IH) is the leading metabolic risk factor for urolithiasis and affects all age groups without gender or race predominance. IH has a high morbidity with or without lithiasis and reduced bone mineral density (BMD), as described previously in pediatric patients as well as in adults. The pathogenesis of IH is complex and not completely understood, given that urinary excretion of calcium is the end result of an interplay between three organs (gut, bone and kidney), which is further orchestrated by hormones, such as 1,25 dihydroxyvitamin D, parathyroid hormone, calcitonin and fosfatonins (i.e., fibroblast growth-factor-23). Usually, a primary defect in one organ induces compensatory mechanisms in the remaining two organs, such as increased absorption of calcium in the gut secondary to a primary renal loss. Thus, IH is a systemic abnormality of calcium homeostasis with changes in cellular transport of this ion in intestines, kidneys and bones. Reduced BMD has been demonstrated in pediatric patients diagnosed with IH. However, the precise mechanisms of bone loss or failure of adequate bone mass gain are still unknown. The largest accumulation of bone mass occurs during childhood and adolescence, peaking at the end of the second decade of life. This accumulation should occur without interference to achieve the peak of optimal bone mass. Any interference may be a risk factor for the reduction of bone mass with increased risk of fractures in adulthood. This review will address the pathogenesis of IH and its consequence in bone mass.

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.

Pediatric urolithiasis: causative factors, diagnosis and medical management

Childhood urolithiasis is associated with considerable morbidity and recurrence. Many risk factors--including those metabolic, genetic, anatomic, dietary and environmental in nature--have been identified in children with urinary tract calculi. As pediatric urolithiasis with a metabolic etiology is the most common disease, evaluating the metabolic risk factors in patients is necessary to both effectively treat current stones and prevent recurrence. We discuss causative risk factors of pediatric urolithiasis, as well as the diagnostic and therapeutic approaches.

Clinical presentation and metabolic features of overt and occult urolithiasis

Although pediatricians are frequently confronted with patients presenting urolithiasis symptoms without obvious stones, the syndrome of occult urolithiasis may be still viewed with some skepticism. We have compared the clinical and metabolic features of 197 children with obvious calculi, 189 with microcalculi (diameter ≤ 3 mm based on renal sonography), and 114 with symptoms of urolithiasis and normal renal sonography findings. Only microcalculi and normal sonography subjects with a urinary abnormality potentially leading to urolithiasis were included in the study. Age at presentation increased significantly (p = 0.0001) in the groups in the order normal sonography to microcalculi to calculi groups. There was no significant difference among the three groups in terms of family history of urolithiasis, gender distribution, and degree of hypercalciuria, hyperuricosuria, hyperoxaluria, or hypocitraturia. The average frequency of pain attacks of patients with recurrent abdominal pain (RAP) ranged from 3.6 to 4.6 days of pain per month among the three groups, which is four to ninefold lower than that reported for children with functional or organic gastrointestinal RAP. The consistency of many clinical and urinary metabolic characteristics indicates a common underlying disorder in overt and occult urolithiasis. The increase of age at presentation from the normal sonography to microcalculi and calculi groups may reflect progressive crystal accretion leading ultimately to overt stone formation.

Longitudinal study of bone mineral density in children with idiopathic hypercalciuria

Children with idiopathic hypercalciuria (IH) may have a reduced bone mineral density (BMD), which could impact on bone health in adulthood. There is currently no strong evidence for a preferred treatment of such children. The aim of our study was to evaluate the BMD z-score before and after treating children and adolescents with IH with potassium citrate and thiazides. The study consisted of a historical cohort of 80 pediatric patients who were evaluated between October 1989 and November 2010. Bone scanning and densitometry measurements were made with dual-emission X-ray absorptiometry. Lumbar-spine BMD (g/cm(2)) and BMD z-score were evaluated before and after treatment. The t test and Mann-Whitney U test were used for statistical analysis. Forty-three boys and 37 girls were followed for a median time of 6.0 years. Median calcium excretion before and after treatment was 5.0 and 2.6 mg/kg/24 h, respectively. The BMD z-score changed significantly from -0.763 ± 0.954 (mean ± SD) to -0.537 ± 0.898 (p < 0.0001) before and after treatment, respectively. The BMD z-score of the patients improved with treatment, suggesting a beneficial effect and potential need for treatment. However, the lack of a control group points to the need for future studies to corroborate this outcome.

Body fat composition and occurrence of kidney stones in hypercalciuric children

In the last 10 years, the incidence of kidney stones has increased in the pediatric population, and this rise has been paralleled by a significant increase in pediatric obesity rates in the USA. The purpose of this study was to evaluate percentage body fat (%BF) measured by dual energy X-ray absorptiometry (DXA) in hypercalciuric children with and without kidney stones. A retrospective chart review was performed on children with idiopathic hypercalciuria based on a 24-h urine calcium excretion of >4 mg/kg/day or >200 mg/day who had undergone DXA scanning. Patients were then classified by sex and by %BF (3 categories; normal: <27% girls, <21% boys; at risk for obesity: 27-36% girls, 21-30% boys; obese: >36% girls, >30% boys). The 2003-2004 NHANES data were used as a control. Fifty patients (24 males) were analyzed, of whom 26% were assessed as having a normal %BF, 44% as being at risk for obesity, and 30% as being obese. Children with an increased %BF had a significantly higher occurrence of kidney stones (p = 0.03) than those with a normal %BF. No significant differences were noted in 24-h urine chemistries between the groups. In conclusion, an increased %BF was associated with an increased occurrence of kidney stones in children with idiopathic hypercalciuria.

Nephrocalcinosis and urolithiasis in children

The incidence of adult urolithiasis has increased significantly in industrialized countries over the past decades. Sound incidence rates are not available for children, nor are they known for nephrocalcinosis, which can appear as a single entity or together with urolithiasis. In contrast to the adult kidney stone patient, where environmental factors are the main cause, genetic and/or metabolic disorders are the main reason for childhood nephrocalcinosis and urolithiasis. While hypercalciuria is considered to be the most frequent risk factor, several other metabolic disorders such as hypocitraturia or hyperoxaluria, as well as a variety of renal tubular diseases, e.g., Dent's disease or renal tubular acidosis, have to be ruled out by urine and/or blood analysis. Associated symptoms such as growth retardation, intestinal absorption, or bone demineralization should be evaluated for diagnostic and therapeutic purposes. Preterm infants are a special risk population with a high incidence of nephrocalcinosis arising from immature kidney, medication, and hypocitraturia. In children, concise evaluation will reveal an underlying pathomechanism in >75% of patients. Early treatment reducing urinary saturation of the soluble by increasing fluid intake and by providing crystallization inhibitors, as well as disease-specific medication, are mandatory to prevent recurrent kidney stones and/or progressive nephrocalcinosis, and consequently deterioration of renal function.

Renal stones: evolving epidemiology and management

The incidence of renal stones in adults has increased significantly over time. Although published evidence is somewhat limited, during the last 10 years, there have been reports of 4-fold increase in the number of children evaluated for nephrolithiasis, and of those, a 7-fold increase in diagnosis of stone disease. The etiology of stone formation has shifted over time, with a transition from infectious causes to metabolic causes. It was our goal in this review of the literature on pediatric renal stone disease to further highlight the changing epidemiology and etiology as well as provide a framework for appropriate clinical evaluation and use of diagnostic tools when approaching a patient with suspected renal stone disease. We also provide guidance regarding treatment and prevention of renal stone disease in children.

The increasing pediatric stone disease problem

While once thought to be relatively rare in developed nations, the prevalence of pediatric urolithiasis appears to be increasing, and a number of factors may be contributing to this increase. Many theories are plausible and such theories include the increasing childhood obesity epidemic, a changing sex predilection, climate change, alterations in dietary habits and improving diagnostic modalities. Yet, unlike adult patients, rigorous epidemiologic studies do not exist in pediatric populations. Thus, in the setting of an increasing prevalence of childhood stone disease, improved research is critical to the development of uniform strategies for pediatric urolithiasis management.

Nutritional aspect of nephrolithiasis

Nephrolithiasis is associated with a variety of abnormalities in urinary composition. These abnormal urinary risk factors are due to dietary indiscretions, physiological-metabolic disturbances or both. Stone disease is morbid and costly, and the recurrence rates may be as high as 30-50% after 5 years. Efforts to prevent stone formation are, therefore, essential. Dietary factors play an important role in kidney stone formation. Tailored dietary recommendations based on metabolic evaluation should be offered to patients for the prevention of recurrence of stone formation. Dietary intervention and subsequent evaluations of therapeutic efficacy should be based on results from multiple 24-h urine collections. Urine flow of >1 ml/kg/h almost eliminates the risk of supersaturation for calcium oxalate, calcium phosphate and uric acid, thus protecting from the formation of corresponding kidney stones. In patients with cystenuria, the required urine flow may even be higher and, in cases such as primary xanthinuria, high fluid intake is required. Milk intake in these patients should be within the RDA of calcium and protein. In children, recommendation of a high fluid intake has only limited success. Nevertheless, each patient should be advised about adequate fluid intake to increase urine volume in accordance with body size. Although children with hypocitraturia may benefit from therapeutic agents that raise the urine citrate concentration, all children bearing residual fragments should be counseled on adequate fluid intake along with potassium citrate treatment to prevent stone regrowth or formation.

Essential oil terpenes: adjunctive role in the management of childhood urolithiasis

Essential oil preparation of the terpenic type was introduced for the first time in the 1930s for the management of urolithiasis. Although essential oil preparations are registered in 50 countries, including some developed countries such as the United Kingdom, Italy, and Japan, for use in urolithiasis, no literature has been published in a peer-reviewed English (Anglo-American) medical journal. Recently the use of these terpenes has been investigated in children with urolithiasis and underlying metabolic abnormalities. The aim of this article is to extract the useful and worthy information about the use of these terpenes in urolithiasis from the previous literature as many of these articles are now considered of poor quality for a thorough systematic scientific review. The main disadvantages of most of the old literature about terpenes are the treatment was not followed radiologically and most of these articles represent anecdotal reports of spontaneous passage of calculi and symptomatic improvement of colic in association with the use of terpenes. The other aim is to discuss the possible role of essential oil terpenes in the management of childhood urolithiasis.

Urolithiasis in the first year of life

Data on urolithiasis (UL) in infancy are limited. The objective of this study was to increase awareness of infant UL and to investigate the influence of possible risk factors in this very specific age group. Nonfasting, second-voiding urine samples were obtained to test for urinary excretions of calcium, oxalate, citrate, magnesium, uric acid, and creatinine. Blood analysis included calcium, phosphate, magnesium, uric acid, creatinine, sodium, potassium, chloride, and alkaline phosphatase. Patients received follow-up testing every 1-2 months; serial ultrasonography was used to track UL status. Fifty infants with a median age of 5 months were enrolled in the study. Hypercalciuria was detected in 9/47, hyperoxaluria in 5/39, hypocitraturia in 4/31, and cystinuria in 2/50 infants. We identified at least one metabolic abnormality in 46% of our patients; no metabolic abnormality was identified in 27 infants. Within a mean follow-up period of 14 months, 17 infants became stone free, stones increased in number in ten patients and decreased in number in 16, and recurrence was detected in seven. This study showed that UL could be detected in very early life, even in the newborn period, and could be the source of late childhood/adulthood UL. Infants with nonspecific symptoms such as restlessness may have UL and should undergo ultrasonographic examination. Metabolic evaluation of UL in this specific age group carries some diagnostic challenges, e.g. unsatisfactory data regarding normal ranges of urinary mineral excretion, and collection of 24-h urine samples.

Recurrent abdominal pain in childhood urolithiasis

OBJECTIVE

Our goal was to establish the clinical presentation and features of pain attacks in children with recurrent abdominal pain (RAP) and urolithiasis.

METHODS

We compared the rate of previous appendectomy among 100 consecutive patients with that of 270 control subjects. We also compared the frequency of pain attacks with that reported by children with functional or organic gastrointestinal RAP.

RESULTS

Fifty-three patients had no history of dysuria or gross hematuria, and only 35 had hematuria at the first visit; 41 patients were evaluated for urolithiasis only because of a family history of kidney stones associated with RAP. Twenty-nine patients had been previously hospitalized for abdominal symptoms. Sixteen patients and 4 control subjects (1.5%) had undergone a previous appendectomy (P < .0001). Two to 28 months before the diagnosis of urolithiasis, 37 patients underwent abdominal ultrasonography, which did not show urinary stones. Sixty-nine percent of subjects younger than 8 years of age had central/diffuse abdominal pain. The mean frequency of pain attacks was 4 to 9 times lower than in patients with functional or organic gastrointestinal RAP.

CONCLUSIONS

Because of the inconstant occurrence of dysuria and hematuria, the location of pain in areas other than the flank, and the lack of calculi shown on imaging studies performed after pain attacks, the urologic origin of pain may be overlooked and ineffective procedures performed. The possibility of urolithiasis should be considered in children with RAP who have a family history of urolithiasis and/or infrequent pain attacks, even when dysuria and hematuria are lacking, and in younger children even when pain is not lateral.

Spontaneous urinary calcium oxalate crystallization in hypercalciuric children

Idiopathic hypercalciuria is the most important predisposing risk factor for calcium oxalate (CaOx) renal stone formation. We assessed the associations between spontaneous CaOx crystallization based on the Bonn Risk Index (BRI), urinary pH, calciuria, oxaluria, and citraturia in 140 Caucasian patients with hypercalciuria, aged 4-17 years, and compared the findings with those in 210 normocalciuric controls. Of the 140 hypercalciuric patients, 58 had renal stones, and 82 had recurrent erythrocyturia, renal colic, or urinary obstructive symptoms-but without stones. Urinary ionized calcium ([Ca(2+)]) levels were measured using a selective electrode, while the onset of crystallization was determined using a photometer and titration with 40 mmol/L ammonium oxalate (Ox(2-)). The calculation of the BRI was based on the [Ca(2+)]:Ox(2-) ratio. The BRI values were 12-fold higher in hypercalciuric children than in healthy controls, but no differences were found in the BRI between subjects with urinary stones and those with urolithiasis-like symptoms. An increased BRI suggested an association with hypercalciuria, lower urinary pH, hypocitraturia, and hypooxaluria. These data indicate that hypercalciuria is an important factor associated with increased urinary CaOx crystallization, although the causal pathways need further investigation. Determination of the BRI in children with hypercalciuria may improve the risk assessment of kidney stones.

Urine calcium/citrate ratio in children with hypercalciuric stones

Hypercalciuria is a common cause for stone formation in children. The aim was to delineate the role of urinary citrate in hypercalciuric children for protection against calcium stone formation. We evaluated random urine calcium, citrate, and creatinine in 149 controls, 78 hypercalciuric nonstone formers, and 34 hypercalciuric children with stone. Urine citrate/creatinine was highest in hypercalciuric nonstone formers 899 +/- 351 compared with controls 711 +/- 328 and stone formers 595 +/- 289 (p < 0.01 vs. both). Calcium/creatinine ratio was similar in hypercalciuric stone and nonstone formers, but significantly higher than controls. Consequently, urine calcium/citrate ratio (mg/mg) increased from control 0.17 +/- 0.17 to 0.41 +/- 0.23 (p < 0.001) in hypercalciuric nonstone formers, and to 0.65 +/- 0.46 in stone formers (p < 0.001 compared with other groups). Area under receiver operating characteristic curve combined with multilevel risk analyses found calcium/citrate ratio of 0.326 to provide good discrimination between control and stone formers. We found 5th percentile for random urine citrate/creatinine ratio in school-aged children to be 176 mg/g, elevated urinary citrate excretion in hypercalciuric children to be protective against stone formation, and urine calcium/citrate ratio to be a good indicator for risk of stone formation. Whether intervention in hypercalciuric children to lower urine calcium/citrate <0.326 will provide protection against stone formation needs to be studied.

Diagnosis and management of hypercalciuria in children

PURPOSE OF REVIEW

In this review, recent advances in the epidemiology, genetics, clinical associations and management of idiopathic hypercalciuria will be discussed.

RECENT FINDINGS

A significant genetic contribution exists in the pathophysiology of hypercalciuria. Although several candidate genes and genetic alterations have been proposed, identification of precise gene(s) responsible remains elusive. Decreased bone density has been increasingly associated with hypercalciuria. Recent publications have suggested that bisphosphonates may play a role in the management in patients in whom both hypercalciuria and decreased bone density are present.

SUMMARY

Idiopathic hypercalciuria is a common disorder in children and can present with a range of clinical presentations such as hematuria, voiding dysfunction, flank pain, abdominal pain, nephrolithiasis, urinary tract infection and decreased bone mineral density. Dietary modifications are often sufficient in the management of hypercalciuria. If the symptoms persist or a rare monogenic disorder is present, consideration should be given to medical treatment with a thiazide diuretic and/or citrate therapy.

Medical treatment of pediatric urolithiasis

In recent years the incidence of pediatric stone disease has increased several fold, mostly due to hypercalciuria and hypocitraturia. The goal of medical treatment is to protect the patient from formation of new stones and expansion of existing ones. The non-pharmacological means to address stone disease include high fluid intake and, frequently, modification of nutritional habits. The pharmacological treatment is based on the chemical composition of the stone and the biochemical abnormalities causing its formation; hence, chemical analysis of the stone, urine and blood is of paramount importance and should be done when the first stone is detected. This review discusses the current options of medical treatment of pediatric urolithiasis.

Low bone density in children with hypercalciuria and/or nephrolithiasis

The objective of this study was to identify how many children with hypercalciuria and/or nephrolithiasis have a low bone density and whether the risk of low bone density can be identified by 24-h urine stone-risk profiles and/or growth parameters. A retrospective chart review was performed on 110 idiopathic hypercalciuria and/or kidney stone patients who received both a 24-h urine for stone-risk profile and a dual-energy X-ray densitometry scan. Patients were divided into low bone density vs. normal bone density groups and hypercalcuria verus nephrolithiasis groups and analyzed for differences in growth parameters, urine stone-risk profiles, and bone densities. Overall, 47% had a bone density z score < -1, and 26% had a bone density z score < -2. Patients with a low bone density had a higher body mass index and lower urine creatinine and ammonium than those with a normal bone density. Patients with nephrolithiasis had a lower bone density z score than patients with hypercalcuria and no nephrolithiasis. Clinicians should be aware of the increased incidence of low bone density in children with hypercalciuria and nephrolithiasis. The effect of hypercalciuria and nephrolithiasis treatment on bone density and the natural progression of the bone density in the studied patient population warrants further investigation.

Risk factors for nephrolithiasis in children

OBJECTIVE

The aim of this study is to evaluate the clinical outcome in children with urinary calculi, to detect risk factors for nephrolithiasis in childhood.

MATERIAL AND METHODS

This retrospective study comprised 62 pediatric nephrolithiasis patients who have come for routine follow-up visits between the dates of January 2002-August 2006 (48% girls and 52% boys).

RESULTS

The mean age of the patients was 8.8 +/- 4.5 years (1-16 years). Hypercalciuria was found in 25 (40%) patients. The mean urinary calcium excretion for hypercalciuric patients was 5.7 +/- 1.2 mg/kg (4.8 mg/kg per day). In our hypercalciuric patients 15 (60%) children had abdominal or flank pain, seven (28%) patients macroscopic hematuria and three (12%) dysuria. Hypocitraturia is the second important risk factor for nephrolithiasis. Urinary calcium excretion showed a positive correlation with the stone size (r = 0.482, P = 0.043). A positive correlation was found between recurrent urinary tract infection (UTI) and hypercalciuria (r = 0.528, P = 0.017). Urinary citrate excretion showed a negative correlation with recurrent UTI (r = -0.503, P = 0.024). Hyperuricaciduria, hyperoxaluria were found to have no effect on the stone size and UTI of the patients. Stones were disintegrated with ESWL in two patients, endoscopic interventions were used in one patient and two underwent an open surgical procedure.

CONCLUSION

All children with nephrolithiasis should have a metabolic screen. Children with a positive family history and consanguinity should be followed carefully with respect to metabolic abnormalities.

Nephrolithiasis

Kidney stones affect more than 5% of adults in the United States, and the prevalence is rising. The fundamental cause for all stones is supersaturation of urine with respect to the stone components; factors affecting solubility include urine volume, pH, and total solute excretion. Calcium stones are the most common in both adults and children and are associated with several metabolic disorders, the most common of which is idiopathic hypercalciuria. Therapy to prevent stones rests on lowering supersaturation, using both diet and medication. Effective treatment decreases stone recurrence and the need for procedures for stone removal.

Screening for hypercalciuria in schoolchildren: what should be the criteria for diagnosis?

The methodologies to diagnose hypercalciuria have not yet been standardized. The aims of this study were to assess the correlation between urinary calcium/creatinine ratio (UCa/Cr) > or = 0.21 (mg/mg) and 24 h urinary calcium excretions and to determine the reference values of the UCa/Cr ratio among a large population of schoolchildren in southern Turkey. Non-fasting, second morning urine samples were collected from 2,143 children aged 7-14 years. In children with suspected hypercalciuria [UCa/Cr > or = 0.21 (mg/mg)], 24 h urine samples were collected. The 95th percentile values of the UCa/Cr ratio for each age were calculated and showed a decrease in value with advancing age. In all, 269 (12.5%) of the children had UCa/Cr > or = 0.21 (mg/mg), of whom 66 (24.5%) had daily urinary calcium excretion > or =4 mg/kg per day. A weak correlation was found between spot UCa/Cr ratios and daily urinary calcium excretions in children with UCa/Cr > or = 0.21 (r = 0.27). We conclude that a spot UCa/Cr ratio of 0.21 (mg/mg) as the upper limit of normal cannot be used universally to define hypercalciuria. Age-specific reference values for UCa/Cr should be established for each population, to be used as a screening test for hypercalciuria, and the definite diagnosis should be established with 24 h urinary calcium excretion whenever possible.

Pathophysiology of hypercalciuria in children

Urinary excretion of calcium is the result of a complex interplay between three organs-namely, the gastrointestinal tract, bone, and kidney-which is finely orchestrated by multiple hormones. Hypercalciuria is believed to be a polygenic trait and is influenced significantly by diet. This paper briefly reviews calcium handling by the renal tubule in normal and in hereditary disorders as it relates to the pathophysiology of hypercalciuria. The effects of dietary sodium, potassium, protein, calcium, and phosphate on calcium excretion, and the association of hypercalciuria with bone homeostasis is discussed, leading to recommendations on means to address excessive urinary calcium excretion.

Idiopathic hypercalciuria in infants with renal stones

In children older than 2 years, hypercalciuria is the most common metabolic cause of renal stones. In infants, its prevalence is not well established. Since 1990, we observed five infants in whom renal stones or microcalculi were diagnosed between the age of 5 and 19 months. One of them was lost to follow up. In the present report, we describe the four patients who underwent metabolic evaluation and in whom idiopathic hypercalciuria (IH) was diagnosed. We conclude that IH is a frequent cause of microcalculi and renal stones in infants, and a screen for this condition is warranted in this age group.

Medical evaluation and treatment of urolithiasis

Nephrolithiasis is responsible for 1 in 1000 to 1 in 7600 pediatric hospital admissions annually throughout the United States. Seventy-five percent of children with nephrolithiasis have an identifiable predisposition to stone formation. This article reviews the different causes and disease states associated with nephrolithiasis in the pediatric population. The initial evaluation and the metabolic evaluation of children with nephrolithiasis are reviewed. Treatment modalities for the different stone types are also described.

Hypocitraturia: a risk factor for reduced bone mineral density in idiopathic hypercalciuria?

The association between idiopathic hypercalciuria (IH) and reduced bone mineral density (BMD) has been described in adults and children. Frequently, hypocitraturia (HC) is an associated condition. To determine the effect that HC may have on bone metabolism of these patients, we studied 88 children with IH at diagnosis, divided into the following groups: group 1-44 (50%) patients with associated HC; group 2-44 (50%) patients without HC; group 3 (29 subjects), a healthy control group. Urinary and blood electrolytes, as long as urinary N-telopeptide, were measured. Lumbar spine (L2-L4) and femoral neck bone mineral density (BMD) and bone mineral content (BMC) were measured by dual energy X-ray absorptiometry. There was no difference in age between the three groups (P=0.80), but weight, height, body mass index, and bone age were lower (P<0.01) and serum intact parathyroid hormone (iPTH) was higher (P<0.05) in group 1 than in groups 2 and 3. N-telopeptide, measured in urine, did not differ between groups. The following bone densitometry parameters: lumbar spine BMC, BMC adjusted for height (BMCh), BMC adjusted for width of vertebrae (BMCw) and BMD, as well as femoral neck BMD, were significantly lower in group 1 than in groups 2 and 3 (P<0.01). When we corrected densitometry parameters for height, BMC was lower in group 1 and not in group 2 when compared with controls.

CONCLUSIONS

Children with IH and associated HC may have a higher risk of bone mass loss and consequent osteopenia. Further studies are needed to assess the role that hypocitraturia may have in this form of bone disease.