Urinary Metabolic Risk Factors Research Articles

Urolithiasis in children; The importance of stone localization in treatment and follow-up.

To evaluate the demographic, etiologic, treatment, and follow-up differences in stones according to their location within the kidney. This retrospective study comprised 337 patients with urolithiasis between 2015 and 2019. Patients were classified into 2 groups according to stone location as lower pole stones (LPS) and upper-middle pole stones (UMPS). The patient's data were recorded at 3-month intervals for one year. One hundred and eighty-three (54.3%) female and 154 (45.7%) men were included in the study. One hundred and twenty-nine (38.3%) of the stones were in the LPS and 208 (61.7%) in the UMPS. UMPS was more common in patients aged > 12months (p < 0.01). At least one metabolic risk factor was present in 93 (72.1%) patients with LPS and 164 (78.4%) with UMPS. The most common urinary metabolic risk factors were hyperoxaluria (31.8%) in patients with LPS and hypocitraturia (34.1%) in patients with UMPS. ROC analysis results showed that cut-off values of 5.5mm for LPS and 6.1mm for UMPS did not provide improve with medical treatment. At the 6- and 12-month follow-ups, the improvement rates were higher in the UMPS group than in the LPS group (p < 0.05). During the follow-up, recurrence was detected in 43 patients: 29% of patients with LPS and 5.8% of patients with UMPS (p < 0.01). Patients with small stones can be followed up. Surgical treatment may be considered for small stones in the LPS. In addition, the risk of recurrence is higher in patients with LPS, and close follow-up is required.

Çocuklarda üriner taş hastalığı: Türkiye’deki bir üçüncü basamak merkez deneyimi

Purpose: The incidence of pediatric nephrolithiasis/urolithiasis (NL/UL) has increased in the last few decades due to dietary habits and a sedentary lifestyle. This study aimed to determine the etiological factors and six months of follow-up results of patients with NL/UL in pediatric nephrology and urology clinics in our center. &#x0D; Materials and Methods: Children with NL/UL between December 2018 and December 2020 were enrolled in this study. The medical records were reviewed to collect data about admission complaints, consanguinity, metabolic risk factors for NL/UL, medical treatments, surgical interventions, and presence of stones after 6 months of follow-up.&#x0D; Results: A total of 93 patients (46 male and 47 female) were included in the study. Consanguinity and a positive family history for stones was present in 46.2% and 78.5% of patients, respectively. The urinary metabolic risk factors were hyperuricosuria (11/83, 13.3%), hypercalciuria (12/93, 12.9%), hyperoxaluria (6/51, 11.8%), cystinuria (7/90, 7.8%), and hypocitraturia (2/41, 4.9%). Twenty patients (29.9%) with NL/UL and without cystinuria received potassium citrate therapy. After 6 months of follow-up (n = 27) of these patients, stone progression was not observed in any of the patients who received potassium citrate treatment (n=11) or underwent surgical intervention (n=10). &#x0D; Conclusions: Most patients had a family history of stones. Hyperuricosuria was the most common urinary risk factor for NL/UL. Potassium citrate therapy might be useful to prevent stone progression in patients with NL/UL.

Metabolic Risk Factors in Infants and Children with Kidney Stones

Background and Objective: In spite of adult renal stones, in pediatric renal stones, most cases have a hereditary background. The evaluation of metabolic risk factors in children with renal stone disease is the basis of medical treatment aimed at preventing recurrent stone events and the growth of preexisting calculi. Therefore, this study was conducted to investigate metabolic risk factors among infants and children with kidney stones in Hamadan Province, Iran, so that it can be the basis for further studies to suggest the elimination of unnecessary diagnostic tests. Materials and Methods: A total of 270 children diagnosed with urinary stones were entered into the study. After recording demographic information, laboratory tests of patients' serum for calcium, phosphorus, sodium, potassium, bicarbonate, uric acid, magnesium, creatinine, and alkaline phosphatase were performed. Moreover, patients' urine was measured for the excretion of random morning samples, such as calcium, oxalate, magnesium, sodium, and uric acid. Results: It was revealed that the male gender had a significant relationship with hypercalciuria and hyperoxaluria. Furthermore, there was a significant relationship of stone size with impaired urine analysis and positive urine culture. Conclusion: Based on the results of this study, urinary metabolic risk factors were widely present in children with urinary stones, and hypercalciuria was the most commonly found disorder. It is recommended that in the evaluation of kidney stones in children, after ruling out the urinary tract abnormalities and infections, metabolic examination of urine be performed, including random measurement of calcium to creatinine in the morning urine, in order to reduce the economic consequences of extensive testing.

Metabolic assessment in pure struvite stones formers: is it necessary?

Background and objective: Magnesium ammonium phosphate stones (MAP), also known as struvite stones, are associated with urinary infection and impairment of renal unit. The aim of this study is to evaluate the urinary metabolic risk factors for recurrence of renal calculi in patients submitted to nephrectomy due to MAP stones.Methods: We retrospectively reviewed the charts of patients > 18 years old submitted to total nephrectomy due to pure MAP stones and pure calcium oxalate (CaOx) stones from July 2006 to July 2016. Urinary metabolic parameters were assessed through 24-hour urine exams ≥ 3 months after nephrectomy. Urinary metabolic parameters and new event related to lithiasis were compared.Results: Twenty-eight and 39 patients were included in MAP and CaOx group, respectively. Abnormalities in 24-hour urine samples were similar between groups. Hypercalciuria occurred in 7.1 and 10.3% of patients in MAP and CaOx group, respectively (p = 0.66), whereas hypocitraturia was present in 65.2 and 59.0% of patients with MAP and CaOx group, respectively (p = 0.41). No significant difference in new events was found between MAP and CaOx groups (17.9 vs. 23.1%, respectively; p = 0.60).Conclusion: A 24-hour urine evaluation should be offered to patients submitted to nephrectomy due to pure MAP stones in order to detect metabolic risk, improve treatment, and prevent stone recurrence.

An observational, prospective and comparative study to assess metabolic abnormality in patients of urolithiasis in paediatric age group in a tertiary care center of Bihar

Introduction: In paediatric age group urolithiasis is less common with overall occurrence rate of only 2-3% of total cases. Children with urolithiasis are related with significant morbidity. Different metabolic parameters either serum or urinary gets deranged in urolithiasis. Evaluation of these parameters help in identification and diagnosis of children who are at increased risk for recurrent stone formation and can be prevented by treating these abnormalities. In this study serum and urinary metabolic risk factors for urolithiasis in children were evaluated, observed and compared. Materials and Methods: This was an observational, prospective and comparative study on fifty (n=50) children with confirmed diagnosis of urolithiasis below 12 years of either sex. Dietary history, water intake and results of laboratory findings (Serum, urinary parameters and stone analysis) were recorded, evaluated, tabulated and analysed using GraphPad Instat Software. All urine samples were obtained from patients without dietary restrictions. Results: Out of 50 children, 35 (70%) and 15 (30%) were male and female respectively. Twenty-three participants were below five years of age. On dietary habits low calcium intake and high calcium intake was seen in 60% (n=30) and 14% (n=7) respectively. 64% (n=32) children had low 24-hour urine volume due to low water intake. 64% (n=32) children had metabolic abnormality and out of them serum abnormality was found in 21 and 24-hour urinary metabolic abnormality seen in 11 children. Hypocalcaemia with normal PTH and secondary hyperparathyroidism was seen in 85.71% (n=18) and 14.29% (n=3) of children respectively. Out of 11 children with urinary metabolic abnormality, hypocitruria (n=6) was the most common followed by hypercalciuria (n=3). Stone analysis was done in 20 patients, out of which majority (n=11, 55%) of the children had calcium oxalate stone. Conclusions: Predominant finding from this study was low urine volume seen due

Metabolic risk factors in children with kidney stone disease: an update.

The prevalence of kidney stones in children has significantly increased in the past few decades, with concomitant increased morbidity and healthcare costs worldwide. Assessing metabolic risk factors is essential for diagnosis and specific treatment. The objective of this retrospective study is to identify the epidemiological and clinical characteristics of children under 17years of age, as well as the metabolic risk factors of nephrolithiasis. A total of 300 children with kidney stone disease were included to undergo several clinical tests using a standardized protocol. The mean age was 11.2years, and the male:female ratio was 1.15:1.0. Biochemical abnormalities were found in 89.3% of all cases. A single urine metabolic risk factor was present in 52.6% (n = 141) of the patients, and multiple risk factors were present in 36.7% (n = 106). Idiopathic hypercalciuria (alone or in combination) and hypocitraturia (alone or in combination) were the most frequent risk factors identified in 47.0% and 39.6% of these patients, respectively. Renal colic and/or unspecified abdominal pain were the most frequent forms of presentation (76.9%), followed by hematuria in 64.4% with 97.5% of stones located in the upper urinary tract. A positive family history in first-degree and second-degree relatives was found in 64.8% of boys and 61.8% of girls. We conclude that specific urinary metabolic risk factors can be found in most children with kidney stones, with hypercalciuria and hypocitraturia being the most common diagnoses. Graphical abstract .

Idiopathic calcium nephrolithiasis with pure calcium oxalate composition: clinical correlates of the calcium oxalate dihydrate/monohydrate (COD/COM) stone ratio.

Pure calcium oxalate is the most frequent type of idiopathic kidney stone composition. Fourier transform infrared spectroscopy (FT-IR) allows to detect the ratio of calcium oxalate dihydrate (COD) and monohydrate (COM) crystals in stones, but the clinical significance of this parameter remains uncertain. The objective of this observational study was to verify the association of clinical and laboratory parameters of kidney stone disease with COD/COM ratio in a group of 465 (322M, age 46 ± 14) patients suffering from idiopathic calcium nephrolithiasis with pure calcium oxalate stones (≥ 97%). Each participant underwent a complete clinical examination, serum chemistry, 24-h urine collection for the determination of the profile of lithogenic risk, and had stones analyzed by FT-IR. Most (62%) of the stones had a COD/COM ratio ≤ 0.25, and the urine chemistry of the corresponding patients showed a low prevalence of urinary metabolic abnormalities. With increasing COD/COM ratio intervals (0-0.25, 0.26-0.50, 0.51-0.75, 0.76-1), a significant association was observed for the number of urological procedures, serum calcium, 24-h urinary calcium excretion, prevalence of hypercalciuria and relative calcium oxalate supersaturation, and a negative trend was detected for the age of the first stone episode (all p values < 0.05). A linear regression model showed that the only parameters significantly associated with COD/COM ratio were 24-h urinary calcium excretion (standardized β = 0.464, p < 0.001) and urine pH (standardized β = 0.103, p = 0.013). In pure calcium oxalate idiopathic stones, COD/COM ratio may reflect the presence of urinary metabolic risk factors, and represent a guide for the prescription of urinary analyses.

Obesity and stones.

The incidence of urolithiasis has shown a prominent increase in the last two to three decades and evidence-based data have clearly indicated the certain role of obesity and overweight in both children and adults. As a certain component of metabolic syndrome, 'obesity' has been found to have a significant impact on the urinary metabolic risk factors which may be important in stone formation. In this present review article, we aimed to evaluate the possible association between obesity and urolithiasis and related risk factors. The epidemiology, pathophysiology, and management of stone disease in obese cases will be discussed in detail. The possible influence of overweight/obesity on the metabolic stone-forming risk factors has been subjected to several studies which in turn well demonstrated the increased risk of stone formation in this population. Although the exact underlying mechanisms are still to be outlined, some certain pathogenetic factors, namely, changes in urinary pH and increased excretion of some urinary stone components have been well demonstrated. Given this increased risk status, these cases require a more comprehensive workup for urolithiasis. Appropriate metabolic evaluation-based medical therapy alongside dietary recommendations will be effective in preventing stone formation. Patients suffering from obesity problem have particular risk factors for urolithiasis when compared with their normal-weight counterparts. All efforts should be taken to increase the awareness of this problem and necessary precautions with well-planned treatment plan are the main tasks for urologists.

Effects of statin treatment with atorvastatin on urolithiasis-associated urinary metabolic risk factors: an experimental study.

To investigate whether atorvastatin has favorable effects on urinary metabolic risk factors associated with urolithiasis. Sixteen male Sprague-Dawley rats were randomly divided into two groups, and baseline spot and 24-h urine samples were collected. Distilled water and atorvastatin were administered to rats during 4weeks in the control and atorvastatin groups, respectively. At the end of the experimental procedure, spot and 24-h urine samples were collected again. Citrate, oxalate, cystine, uric acid, calcium and magnesium levels were determined in 24-h urine samples. Citrate/creatinine, oxalate/creatinine, uric acid/creatinine, calcium/creatinine and magnesium/creatinine ratioswere also calculated in spot urine samples. Comparison of the baseline and post-experimental levels of these parameters was made in each group. The majority of the parameters were similar before and after the experimental procedure in each group. In the atorvastatin group, uric acid and calcium levels were affected. Administration of atorvastatin was significantly decreased the levels of uric acid, whereas increased the levels of calcium (P=0.025 and P=0.017, respectively). Our study revealed that atorvastatin has decreasing effect on UUa levels, whereas increasing effect on UCa levels. We think it cannot certainly be deduced that atorvastatin could be beneficial on overall urinary metabolic risk factors. Contrarily, atorvastatin may lead to an increased risk of calcium stones, but when considering its UUa decreasing effect, it may help in reducing the uric acid stone recurrence.

Clinical Characteristics and Metabolic Abnormalities in Pediatric Urolithiasis in South East Iran

Introduction: To investigate clinical presentation, metabolic risk factors and urinary tract abnormalities in paediatric urolithiasis. Materials and Methods: Between 2011 and 2012, 100 children (53 boys and 47 girls) were treated for urolithiasis. Clinical presentation, calculus localisation, urinary tract infection status, presence of anatomic abnormalities and urinary metabolic risk factors were retrospectively evaluated.Results: The most common clinical features on admission were restlessness/irritability (62%), flank pain (33%) and gross hematuria (4%). Twenty-one percent of patients were detected incidentally during evaluation for other conditions. Urine random tests revealed metabolic abnormalities, including hypercalciuria (56%) and hypocitraturia (64%) in most cases. Anatomic malformation (32%) and urinary tract infections (UTI)(9%) were other presentations.Conclusions: We concluded that most patients were symptomatic and hypocitraturia was the most common risk factor.Keywords: Urolithiasis; Urinary Tract; Pediatrics, Demographic Factor; Hypercalciuria.

Effect of being overweight on urinary metabolic risk factors for kidney stone formation.

The prevalence and incidence of kidney stone disease have increased markedly during the past several decades, and studies have demonstrated that inappropriate dietary habits are leading to more obesity and overweight (OW) in children and adults, which may be important in stone formation. Obese and OW patients share most of the same risk factors for cardiovascular morbidity, while the impact of being OW, rather than obese, on urinary metabolic parameters of kidney stone formers (KSF) is less well known. The aims of this study were to investigate urinary metabolic parameters, stone composition and probability of stone formation (Psf) in OW KSF when compared with normal weight (NW) and obese KSF. The kidney stone database for KSF attending a large metabolic stone clinic was investigated. Patients with a recorded BMI, confirmed diagnosis of kidney stone disease and full metabolic evaluation were divided into three categories: BMI ≤25.0 kg/m(2) (NW group), BMI 25-30 kg/m(2) (OW group) and BMI >30.0 kg/m(2) (obese group). Twenty-four hour urinary volume (U.Vol), pH (U.pH), calcium (U.Ca), oxalate (U.Ox), citrate (U.Cit), uric acid (U.UA), magnesium (U.Mg), sodium (U.Na) and potassium (U.K) excretions, along with stone composition and Psf, were then compared among the groups. A total of 2132 patients were studied, of whom 833 (39%) were NW, 863 (40.5%) were OW and 436 (20.5%) were obese. OW and obese KSF were older (mean age 43 ± 15 in NW, 48 ± 13 in OW and 50 ± 12 years in obese; P for trend <0.001), demonstrated increased female predominance and higher prevalence of diabetes, hypertension and gout. There were no statistically significant differences in U.Vol and U.Mg among the groups. However, significantly higher levels of U.Ca, U.Ox, U.Cit, by crude analysis, and U.UA (3.3 ± 1.1 versus 3.8 ± 1.2 versus 4.0 ± 1.2 mmol/L; P < 0.001 for trend), U.Na (151 ± 57 versus 165 ± 60 versus 184 ± 63 mmol/L; P < 0.001 for trend), and lower U.pH (6.3 ± 0.5 versus 6.1 ± 0.5 versus 6.0 ± 0.6; P < 0.001 for trend) by both crude and multivariate adjusted analysis models were demonstrated in OW and obese KSF. Stone composition data (N = 640) showed a significantly higher incidence of uric acid stones in OW and obese groups (P for trend < 0.001). In addition, higher Psf for CaOx, UA and CaOx/UA stone types were detected in OW and obese compared with NW KSF. Similar to obese KSF, OW KSF show clear alterations in metabolic urinary profiles that are associated with increased overall risk of stone formation. This greater risk is primarily due to raised U.UA and U.Na, lower U.pH and higher prevalence of hypercalciuria, along with unchanged levels of the commonly measured urinary lithogenesis inhibitors. Moreover, our study established a higher incidence of uric acid, but not calcium, stones in OW KSF. Thus, appropriate evaluation and follow-up may be warranted even in OW patients who are at risk of increased stone formation. Whether modest weight loss in OW KSF will have a favourable impact on their metabolic urinary profiles and thereby diminish the risk of further stone formation needs exploring.

Editorial Comment

Obesity is a significant epidemic, with far reaching health implications. It is estimated that >30% of the adult US population are obese and the prevalence rates will continue to increase rapidly. 1 Natarajan V. Master V. Ogan K. Effects of obesity and weight loss in patients with nononcological urological disease. J Urol. 2009; 181: 2424-2429 Abstract Full Text Full Text PDF PubMed Scopus (13) Google Scholar Obesity is associated with heart disease, hypertension, sleep apnea, and type II diabetes. Salient to urologists is the association of renal lithiasis and obesity. Bariatric surgery as a means of surgical treatment of obesity has become increasingly popular, with an estimated 177 600 surgeries performed in the United States in 2006. 2 American Society for Metabolic and Bariatric Surgery http://www.asbs.org Google Scholar Asplin and Coe 3 Asplin J.R. Coe Fl Hyperoxaluria in kidney stone formers treated with modern bariatric surgery. J Urol. 2007; 177: 565 Abstract Full Text Full Text PDF PubMed Scopus (135) Google Scholar demonstrated that the most common bariatric surgery, the Roux-en-Y gastric bypass (RYGB), results in significant hyperoxaluria and supersaturation of calcium oxalate as early as 3 months postprocedure. Matlaga et al 4 Matlaga B.R. Shore A.D. Magnuson T. et al. Effect of gastric bypass surgery on kidney stone disease. J Urol. 2009; 181: 2573-2577 Abstract Full Text Full Text PDF PubMed Scopus (107) Google Scholar recently reported that RYGB surgery results in a higher incidence of renal lithiasis as compared with a cohort of control subjects, with BMIs >35 and matched on the basis of age, gender, and comorbid conditions. Are obese patients contemplating weight control surgery “caught between a rock and a hard place”? This study appears to offer some promise. The authors demonstrate that gastric banding (GB), a surgical alternate to the RYGB, is not associated with an increased risk of renal lithiasis or kidney stone surgery. They compared a cohort of patients who underwent GB with a control group of patients having BMI >35 and matched by age, gender, and comorbid conditions. The addition of a third cohort who underwent the more popular RYGB may have added to the study. Although the finding of no apparent increased risk of lithiasis associated with the GB technique is encouraging, this positive finding should be tempered because of the relatively short-term follow-up in this study. Nonetheless, the authors should be commended for addressing the risk of lithiasis in patients undergoing weight-reduction surgery. The positive findings of this study should encourage further investigation into the metabolic association of renal lithiasis and the different methods of bariatric surgery. ReplyUrologyVol. 74Issue 4PreviewIn light of the obesity epidemic, which threatens to redefine the nature of medical care, surgical procedures that can bring about significant and lasting weight loss will continue to increase at a fast rate. In the short term, and unlike the Roux-en-Y gastric bypass, gastric banding does not appear to be associated with an increased risk for kidney stone disease or kidney stone surgery. However, long-term studies are imperative to confirm these encouraging findings. Equally helpful will be prospective studies that evaluate changes in urinary metabolic risk factors following restrictive surgical procedures such as gastric banding. Full-Text PDF The Effect of Gastric Banding on Kidney Stone DiseaseUrologyVol. 74Issue 4PreviewTo evaluate the likelihood of being diagnosed with, or treated for, an upper urinary tract calculus after gastric banding. Bariatric surgical procedures are being increasingly utilized in the treatment of patients with morbid obesity. Certain malabsorptive bariatric procedures have been associated with an increased risk for kidney stone formation. However, the kidney stone risk of gastric banding, a restrictive bariatric procedure, is unknown. Full-Text PDF

Bone Disease in Medullary Sponge Kidney and Effect of Potassium Citrate Treatment

In medullary sponge kidney (MSK)-a common malformative renal condition in patients with calcium nephrolithiasis-hypercalciuria, incomplete distal renal tubular acidosis, and hypocitraturia are common. Clinical conditions with concomitant hypercalciuria and/or incomplete distal renal tubular acidosis are almost invariably associated with bone disease, making osteopathy highly likely in MSK, too. Patients with MSK have never been investigated for osteopathy; neither has the potential effect of potassium citrate administration (CA) on their urinary metabolic risk factors and on bone mineralization. These issues were retrospectively analyzed in 75 patients with MSK and primary stone risk factor (PSRF; hypercalciuria, hypocitraturia, hyperuricosuria, and/or hyperoxaluria) on an outpatient basis; 65 received CA (2.9 +/- 0.8 g/d), whereas 10 received only general "stone clinic" suggestions. The 24-h urinary excretion of calcium, phosphate, oxalate, uric acid, and citrate; morning urine pH; serum biochemistry; and bone mineral density were investigated at baseline and at the end of follow-up (78 +/- 13 and 72 +/- 15 mo in groups A and B, respectively). CA led to a significant rise in urinary pH and citrate and decreased urinary calcium and phosphate (all P < 0.001). Patients with MSK and PSRF had reduced bone density. Bone density improved significantly in the group that was treated with oral CA. Bone disease is very frequent in patients with MSK and concomitant PSRF. Long-term CA improves bone density. The concurrent effects of treatment on PSRF suggest that the subtle acidosis plays a pivotal role in bone disease and hypercalciuria in patients with MSK.

Changes in Urinary Lithogenic Features Over Time in Patients With Urolithiasis

To assess the changes and sex-specific differences in urinary metabolic risk factors with time. We performed a retrospective analysis of 619 patients with first-time calcium stone formation (SF) with complete metabolic assessments, who had been diagnosed and treated from 1994 to 2007 at our institution. Patients with SF were categorized into 2 groups according to the date of initial diagnosis: group 1 (1994-1999, n = 353 [57.0%]) and group 2 (2000-2007, n = 266 [43%]). The incidence of obesity was greater in group 2 than in group 1, and this difference was statistically significant among male patients with SF. The urinary pH and total urine volume were lower and the excretion of uric acid was greater in group 2 than in group 1. The incidence of metabolic abnormalities such as low urine volume was more common in group 2 than in group 1. The incidence of hyperuricosuria was increased in male patients with SF in group 2 compared with that in the men in group 1. However, no significant differences were found in the incidence of hyperuricosuria in the female patients with SF between groups 1 and 2. The pattern of urinary lithogenic factors in Korean patients with SF has changed with time. Hyperuricosuria has become more prevalent in recent years. We found a high prevalence of hyperuricosuria in men, which might have been due to the increased incidence of obesity in this subgroup.

Diagnosis and spectrum of melamine-related renal disease: Plausible mechanism of stone formation in humans

Background An epidemic of urinary stones affecting children after consumption of melamine tainted milk is unfolding. We defined clinicopathological features of the disease for diagnosis, monitoring, and treatment of this group of patients. Methods A clinicopathological study on exposed children with ultrasonographic evidence of urolithiasis was conducted. Melamine and cyanuric acid levels in the urine were determined by mass spectrometry. Results Disease severity varied from acute renal failure with hydronephrosis to symptomatic or asymptomatic stones with or without abnormal urinalysis. All cases were aged < 3 y with > 50% cases having predisposing urinary metabolic risk factors for urolithiasis. Most of the stones were located in the renal pelvis and measured 2.5–18 mm by ultrasonography. We found a strong correlation between renal stone size and urinary melamine concentration. For stones < 10 mm, a 10 μg/mmol creatinine increase in urinary melamine concentration is associated with approximately 1 mm increase in the size of the stone. The high degree of correlation strongly suggests that melamine is related to stone formation in humans. Using ROC analysis, we propose that patients who have a persistent melamine level above the optimal cut-off value of 7.1 μg melamine/mmol creatinine in urine might have a significant exposure of melamine-tainted products. Unlike melamine, urinary cyanuric acid is not significantly different between cases and controls. Pathophysiological findings from feeding animals with melamine and cyanuric acid may not be directly applicable to humans. Conclusion Both melamine and urine metabolic lithogenic factors are important for the formation of melamine-related stones. Apart from aiding with case screening and confirmation, the urine melamine level might as well be an indicator of residual melamine load in the body and thus is useful for following-up and monitoring of the confirmed cases. As the stones are small and can be passed out spontaneously, follow-up of these patients with urine melamine will be a convenient tool for monitoring the melamine load of the patients.

Pediatric urolithiasis: an 8-year experience of single centre

The objective was to investigate the clinical features and metabolic and anatomic risk factors for kidney stone formation in our patient group. Between 1998 and 2005, 179 children (94 girls, 85 boys) followed in our department because of urolithiasis were enrolled to participate in our study. Clinical presentation, urinary tract infection, stone localisation, positive family history, stone composition, presence of anatomic abnormalities and urinary metabolic risk factors, and treatment modality were evaluated retrospectively. The mean age at diagnosis of stone disease was 4.5 years (range 0.25-15.3 years). The mean follow-up duration was 8 months (range 1-98). The major clinical presentations of our patients were abdominal pain and/or flank pain in 100 children (55.9%) and macroscopic hematuria in 25 (14%). Urinary tract infection was detected in 20% of patients on admission. Forty-three children (24%) had a urinary tract abnormality and ureteropelvic junction obstruction was the most common abnormality. A family history of stone disease was recorded in 98 patients (54.7%). Stones were located within the renal parenchyma in 90 patients. Hypercalciuria and hyperuricosuria were detected in 42.3 and 54.8% respectively. Stone analysis was performed in 63 children and calcium oxalate was a major mineral. Surgical treatment was performed in 49 children and extracorporeal shock wave lithotripsy (ESWL) in 41 children. We think that urolithiasis remains a serious problem in children in our country. Family history of urolithiasis, urologic abnormalities (especially under the age of 5 years), metabolic disorders and urinary tract infections tend to indicate childhood urolithiasis.