Does obesity or hyperuricemia influence lithogenic risk profile in children with urolithiasis?

Atorvastatin Decreases Renal Calcium Oxalate Stone Deposits by Enhancing Renal Osteopontin Expression in Hyperoxaluric Stone-Forming Rats Fed a High-Fat Diet

Calcium oxalate (CaOx) is the major constituent of kidney stones. Growing evidence shows a close connection between hyperlipidemia, cardiovascular disease (CVD), and the formation of kidney stones. Owing to their antioxidant properties, statins control hyperlipidemia and may ameliorate CaOx stone formation. The present study was designed to investigate the suppressive effects of statins on CaOx urolithiasis and their potential mechanism. We used rats fed a high-fat diet (HFD) to achieve hyperlipidemia (HL) and hydroxyproline (HP) water to establish a hyperoxaluric CaOx nephrolithiasis model; the animals were administered statins (A) for 28 days. The rats were divided into eight groups treated or not with A, i.e., Control, HP, HL, HL + HP. HL aggravated urinary calcium crystallization compared to the control. Due to increased expression of renal osteopontin (OPN), a key anti-lithic protein, and reduced free radical production, the calcium crystals in the urinary bladder increased as renal calcium deposition decreased. The levels of the ion activity product of CaOx (AP(CaOx)) decreased after statins administration, and AP(Calcium phosphate) (CaP) increased, which suggested the dominant calcium crystal composition changed from CaOx to CaP after statin administration. In conclusion, atorvastatin decreases renal CaOx stone deposits by restoring OPN expression in hyperoxaluric rats fed a HFD.

Serum and urine uric acid level may have different predictive value for urinary stone composition: a retrospective cohort study of 718 patients in Chinese population

PURPOSE

We launched a retrospective cohort study to explore the interactions among serum uric acid (UA), urine UA, and stone types.

METHODS

Clinical characteristics of urolithiasis patients in Beijing Tsinghua Changgung Hospital from October 2015 to August 2017 were retrospectively collected. Participants were categorized according to the quartiles of SUA and UUA respectively. Logistic regression model was built to identify the relationship between stone composition and UA level. Cubic spline was fitted to explore the correlation between 24-h urine UA and serum UA.

RESULTS

718 hospitalized patients (51.1 ± 14.3 years, male 63.4%) with urinary calculi were included. Higher serum UA is associated with male, alcohol use, multiple serum and urine electrolytes (e.g. potassium, chloride, calcium, phosphorus), and lower estimated glomerular filtration rate. The risk of UA stone and carbonate apatite stone was associated with serum UA while the risk of calcium oxalate (CaOx) stone and ammonium magnesium hexahydrate (AMH) was dependent on urine UA. In the unadjusted model (Model 1), higher risks of UA stones were observed in the third quartile (OR 3.26, 95% CIs 1.63-6.53, P = 0.001) and the fourth quartile (OR 3.55, 95% CIs 1.78-7.08, P < 0.001) of serum UA compared with the first quartile. The risks of carbonate apatite stone were lowered in the third (OR 0.48, 95% CIs 0.31-0.73, P = 0.001) and fourth quartile (OR 0.40, 95% CIs 0.42-0.98, P = 0.042) of serum UA. The risk of CaOx stone was increased in the fourth quartile (OR 2.14, 95% CIs 1.15-3.99, P = 0.017) while the risk of AMH stone was decreased in the third (OR 0.46, 95% CIs 0.22-0.94, P = 0.034) and fourth quartile (OR 0.35, 95% CIs 0.16-0.78, P = 0.009) of urine UA. The elevated risks of UA stones in high levels of serum UA were demonstrated in the adjusted model (Model 2). An M-shaped association was found between serum UA and urine UA in our population.

CONCLUSIONS

Serum UA and urine UA might cast different impact on urinary calculus composition. Proper control of the parameters should be considered based on different predisposing factors in individual patients.

The prevalence and risk factors of prostatic calculi in Han Chinese: a cross-sectional study based on health examinations

PURPOSE

Prostatic calculi (PCal) are commonly present with prostate disease; we aim to map the incidence and associated clinical risk factors of PCal in Han Chinese.

MATERIAL AND METHODS

We retrospectively selected men who sought a medical check-up in 2018. Basic clinical items, including age, weight, height, prostate specific antigen (PSA), uric acid (UA), fasting blood glucose (FBG), urinalysis results, and transabdominal prostate ultrasound, were recorded. Univariate and logistic regression analyses were performed to evaluate whether these factors were associated with the presence of PCal.

RESULT

We recorded the parameters of laboratory tests and clinical information from 14,427 men; men with PCal comprised 51.65% of the total group and 76.61% of the subgroup of benign prostate hyperplasia (BPH) patients. All the enrolled parameters showed meaningful differences, but the logistic regression analysis only indicated significant effects related to age (OR = 1.044, 95% CI = 1.040-1.047, and p < .001), body mass index (BMI) (OR = 1.035, 95% CI = 1.022-1.048, and p < .001), UA (OR = 0.999, 95% CI = 0.999-1.000, and p = .029), BPH (OR = 2.923, 95% CI = 2.678-3.191, and p < .001), and prostate cysts (OR = 0.609, 95% CI = 0.471-0.788, and p < .001). The odds ratio of the predicted combined model is 1.068.

CONCLUSIONS

PCal was detected in 51.65% of men among healthy Han Chinese and in 76.61% of BPH patients. Age, BMI, UA, BPH, and prostate cysts were independent risk factors for the presence of PCal.

Association between dietary pattern and metabolic disorders in children and adolescents with urolithiasis

OBJECTIVE

To describe the dietary patterns and occurrence of metabolic disorders in children and adolescents with urolithiasis treatment at a referral hospital in southern Brazil in order to learn the features of urolithiasis in this population to better develop preventive actions.

METHODS

Descriptive study conducted between 2016 and 2017 in a tertiary care referral hospital. Fourty patients aged 2-19 years old with urolithiasis proven by imaging were included. Clinical and dietary data were obtained through interviews and medical records. For statistical analyses, the chi-squared test was performed.

RESULTS

40 individuals were analyzed. Mean age at diagnosis was 7.2±4 years. 25% were overweight or obese. 95% had metabolic disorders, hypocitraturia being the predominant type. Protein intake was adequate in all participants and carbohydrate intake, in 70% of them; 37.5% had lipid intake above recommended and 65% had low fiber intake. The mean daily sodium intake was 2.64g (±1.74), with 55% of participants ingesting more than the recommended amount. A total of 52.5% had low potassium intake, with a mean of 4.79g/day (±2.49). Calcium intake was adequate in 27.5%. No significant differences were identified in relation to mean daily consumption among participants with or without the various metabolic disorders.

CONCLUSION

Pediatric urolithiasis is often accompanied by metabolic disorders; therefore, metabolic evaluation should be part of the diagnostic process and subsequent analysis of these patients' dietary patterns, helping to optimize treatment and prevent recurrences and complications.

Evaluation of a child with suspected nephrolithiasis

PURPOSE OF REVIEW

As the incidence of nephrolithiasis in children doubles every 10 years it is becoming a common disease associated with significant morbidity along with considerable economic burden worldwide. The aim of this review is to summarize current data on the epidemiology and causes of renal stones in children and to provide a frame for the first clinical evaluation of a child with suspected nephrolithiasis.

RECENT FINDINGS

Dietary and environmental factors are the driving force of changing epidemiology. Diagnosis should be based on medical history, presenting signs, examination, first laboratory and radiological workup. Ultrasound should be the initial diagnostic imaging performed in pediatric patients while low-dose computed tomography is rarely necessary for management. Metabolic factors including hypercalciuria, hypocitraturia, low fluid intake as well as specific genetic diseases should be explored after the resolution of initial signs and symptoms.

SUMMARY

Appropriate initial evaluation, imaging technique, identification of risk factors and other abnormalities are essential for early diagnosis and prevention of stone-related morbidity in children with suspected nephrolithiasis.

Educational review: role of the pediatric nephrologists in the work-up and management of kidney stones

BACKGROUND

The incidence of nephrolithiasis in children and adolescents is increasing and appears to double every 10 years. The most important role of the pediatric nephrologist is to diagnose and modify various metabolic and non-metabolic risk factors, as well as prevent long-term complications especially in the case of recurrent nephrolithiasis.

OBJECTIVE

The purpose of this review is to summarize the existing literature on the etiology and management of pediatric nephrolithiasis.

RESULTS

The incidence of kidney stones is increasing; dietary and environmental factors are probably the main causes for this increased incidence. In most pediatric patients, the etiology for the kidney stones can be identified. Metabolic factors, such as hypercalciuria and hypocitraturia, urinary tract infection, and urinary stasis, constitute leading causes. Herein, we review the etiologies, diagnostic work-up, and treatment options for the most prevalent causes of kidney stones. The detrimental effects of excessive dietary sodium, reduced fluid intake, and the benefits of plant-based over animal-based protein consumption on urinary crystal formation are discussed. We also review the long-term complications.

CONCLUSIONS

Pediatric nephrologists have an important role in the diagnostic work-up and prevention of recurring nephrolithiasis.

Risk factors for recurrent urolithiasis in children

PURPOSE

To identify risk factors associated with recurrent kidney stones in a paediatric cohort in a Belgian tertiary centre.

STUDY DESIGN AND METHODS

Medical records of children with the first episode of urolithiasis between 1998 and 2016, followed at Ghent University Hospital initially and at least one-year follow-up were retrospectively reviewed. Patient characteristics, past medical history, presenting symptoms, the results of laboratory investigations and the applied management strategy were analysed. The significant variables from the univariate analysis were integrated into a backward conditional multivariate model.

RESULTS

Ninety-seven children were included in the analysis, of which 33 (34%) presented with at least one episode of stone recurrence. In the univariate analysis, body mass index (BMI) > 85th percentile and asymptomatic stones at initial presentation were associated with 1.8 and 0.1 times lower risk of recurrent stones, respectively (p = 0.020, 95% confidence interval (CI):0.368-8.749 and p = 0.017, 95% CI:0.014-0.921). In contrast, immobilization resulted in a 10-times higher risk (p = 0.002, 95% CI:1.968-50.005) and the need for technical intervention was associated with a 3.2- times higher risk (p = 0.017, 95% CI:1.297-8.084) of developing recurrent stones. On multivariate analysis only BMI >85th percentile was associated with a 15 times lower risk of stone recurrence (p = 0.030, 95% CI:0.006-0.739).

DISCUSSION

A possible explanation of reduced risk in patients with a BMI > 85th percentile may lie in a different metabolic profile. Immobilization as a risk factor can be explained by calcium metabolism, which is influenced by immobilization due to fractures, paralysis or motor disability because it causes resorption of the skeleton resulting in elevated blood calcium levels. This study showed that patients who presented without symptoms when the stones first occurred were less likely to have recurring kidney stones compared with patients with symptoms at initial presentation. When technical intervention was needed, we believe this is partly due to a larger stone burden, however we could not find an evidence-based explanation. The institutional protocol, which allowed to create a database with a limited number of patients, was lost to follow-up. Despite the retrospective setting some data were missing. There might also be a bias because the patients were followed-up at a tertiary centre. Possibly, our conclusions cannot be generalized toward the entire paediatric population.

CONCLUSION

Of all the factors investigated in our cohort, BMI >85 th percentile and asymptomatic stones are associated with a lower risk of stone recurrence. Conversely, immobilized patients and those who require technical intervention at initial presentation may benefit from an intense follow-up after the first episode of urolithiasis.

Urolithiasis in children and exposure to melamine: A review of the epidemiological literature

Melamine (ME) is a high production volume compound, mainly used for the synthesis of ME-formaldehyde resins. There is an extensive toxicological and epidemiological database on this compound, but the epidemiology has so far not been reviewed. An extensive literature search in PubMed was conducted and relevant ME epidemiology studies were identified and assessed. The epidemiology data nearly entirely consisted of studies on the health effects due to the food tampering catastrophe in China discovered in 2008 where ME was intentionally added to powdered milk products. Most of these studies were aimed at assessing the extent of the catastrophe and the clinical follow-up of affected children. A reliable dose–response relationship could not be derived from the epidemiology studies. However, they do contain several strong data points that can assist in ranging the No Observed Adverse Effect Level (NOAEL) for humans, for children in particular.

Influence of BMI in nephrolithiasis in an Appalachian pediatric population: A single-center experience

INTRODUCTION

The prevalence of pediatric nephrolithiasis has increased significantly in the past 20 years. Metabolic abnormalities predisposing adults to nephrolithiasis in obese patients include increased urinary sodium and uric acid excretion as well as low urine pH; however, limited data are available in the pediatric population.

OBJECTIVE

The aim was to investigate whether obese pediatric patients presenting with nephrolithiasis have a unique metabolic profile similar to reported findings in obese adults with nephrolithiasis.

STUDY DESIGN

A retrospective chart review was performed in children aged 1-18 years seen at Kentucky Children's Hospital between 2010 and 2016. Inclusion criteria included all patients with documented stones confirmed by ultrasonography or computed tomography.

RESULTS

A total of 111 patient charts were reviewed in the study with a mean age of 11.8 ± 4.2 years. Seventy patients (63%) had a normal BMI and 41 patients (37%) were considered overweight/obese. There was no statistically significant relationship between BMI and stone recurrence. Obese patients had significantly decreased levels of urinary citrate, oxalate, magnesium, and potassium with significant elevations of urinary urea nitrogen, ammonia, and low urine pH compared with normal weight patients (Summary Figure).

DISCUSSION

Several groups have reported on metabolic findings within obese and non-obese pediatric patients. A Turkish study reported increased oxalate excretion and hypocitraturia in obese patients while a Korean study also reported increased rates of hypocitraturia in recurrent stone formers. Similar to these studies, we did find significant differences in citrate within our study population; however, we found significantly lower levels of urinary oxalate in obese patients. The majority of these studies do not report an association with BMI and urine pH although this has been reported in the adult population and our findings support an inverse relationship between body mass index (BMI) and pH. Our group found a higher level of calcium phosphate stones, supporting of Eisner's findings that high BMI is associated with increased supersaturation of calcium phosphate. Limitations of our study include being a single center and retrospective in nature.

CONCLUSION

Our study demonstrates differences in types of stones and urinary metabolites in an obese pediatric population suggestive of different metabolic profiles contributing to stone disease. We report similar association between BMI and urine pH, urinary potassium, and citrate. This study confirmed our primary hypothesis that obese pediatric patients would have a different urinary mineral profile as evidenced by lower levels of citrate and potassium and low urine pH; however, obese patients did not exhibit significantly elevated urinary sodium and uric acid when normalized to weight, as described in the adult population. Our study did not confirm our secondary hypothesis that stone composition would be associated with BMI status or stone recurrence.

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.

GWAS of clinically defined gout and subtypes identifies multiple susceptibility loci that include urate transporter genes

OBJECTIVE

A genome-wide association study (GWAS) of gout and its subtypes was performed to identify novel gout loci, including those that are subtype-specific.

METHODS

Putative causal association signals from a GWAS of 945 clinically defined gout cases and 1213 controls from Japanese males were replicated with 1396 cases and 1268 controls using a custom chip of 1961 single nucleotide polymorphisms (SNPs). We also first conducted GWASs of gout subtypes. Replication with Caucasian and New Zealand Polynesian samples was done to further validate the loci identified in this study.

RESULTS

In addition to the five loci we reported previously, further susceptibility loci were identified at a genome-wide significance level (p<5.0×10-8): urate transporter genes (SLC22A12 and SLC17A1) and HIST1H2BF-HIST1H4E for all gout cases, and NIPAL1 and FAM35A for the renal underexcretion gout subtype. While NIPAL1 encodes a magnesium transporter, functional analysis did not detect urate transport via NIPAL1, suggesting an indirect association with urate handling. Localisation analysis in the human kidney revealed expression of NIPAL1 and FAM35A mainly in the distal tubules, which suggests the involvement of the distal nephron in urate handling in humans. Clinically ascertained male patients with gout and controls of Caucasian and Polynesian ancestries were also genotyped, and FAM35A was associated with gout in all cases. A meta-analysis of the three populations revealed FAM35A to be associated with gout at a genome-wide level of significance (p meta =3.58×10-8).

CONCLUSIONS

Our findings including novel gout risk loci provide further understanding of the molecular pathogenesis of gout and lead to a novel concept for the therapeutic target of gout/hyperuricaemia.

Development of Nephrolithiasis in Asymptomatic Hyperuricemia: A Cohort Study

BACKGROUND

Although the association between gout and nephrolithiasis is well known, the relationship between asymptomatic hyperuricemia and the development of nephrolithiasis is largely unknown.

STUDY DESIGN

Cohort study.

SETTING & PARTICIPANTS

239,331 Korean adults who underwent a health checkup examination during January 2002 to December 2014 and were followed up annually or biennially through December 2014.

PREDICTOR

Baseline serum uric acid levels of participants.

OUTCOME

The development of nephrolithiasis during follow-up.

MEASUREMENTS

Nephrolithiasis is determined based on ultrasonographic findings. A parametric Cox model was used to estimate the adjusted HRs of nephrolithiasis according to serum uric acid level.

RESULTS

During 1,184,653.8 person-years of follow-up, 18,777 participants developed nephrolithiasis (incidence rate, 1.6/100 person-years). Elevated uric acid level was significantly associated with increased risk for nephrolithiasis in a dose-response manner (P for trend < 0.001) in men. This dose-response association was not observed in women. In male participants, multivariable-adjusted HRs for incident nephrolithiasis comparing uric acid levels of 6.0 to 6.9, 7.0 to 7.9, 8.0 to 8.9, 9.0 to 9.9, and ≥10.0mg/dL with uric acid levels < 6.0mg/dL were 1.06 (95% CI, 1.02-1.11), 1.11 (95% CI, 1.05-1.16), 1.21 (95% CI, 1.13-1.29), 1.31 (95% CI, 1.17-1.46), and 1.72 (95% CI, 1.44-2.06), respectively. This association was observed in all clinically relevant subgroups and persisted even after adjustment for homeostasis model assessment of insulin resistance and high-sensitivity C-reactive protein level.

LIMITATIONS

Dietary information and computed tomographic diagnosis of nephrolithiasis were unavailable.

CONCLUSIONS

In this large cohort study, increased serum uric acid level was modestly and independently associated with increased risk for the development of nephrolithiasis in a dose-response manner in apparently healthy men.

Silicate calculi, a rare cause of kidney stones in children

BACKGROUND

Urinary silicate calculi in humans are extremely rare. Reported cases of silicate calculi are mostly documented in adults and are commonly related to an excessive intake of magnesium trisilicate in food or drugs. Published studies on the presence of silicate calculi in children are scarce.

CASES

Three cases of silicate kidney stones without prior silicate intake are reported. Two patients underwent surgical treatment, and the third patient was treated using conservative methods. Urinalysis revealed no underlying metabolic abnormalities. Analyses revealed that silicate was the major component of the stones.

CONCLUSION

Siliceous deposits in urinary stones may be more common than anticipated, and the underlying pathophysiology remains to be clarified.

Dyslipidaemia in overweight children and adolescents is associated with an increased risk of kidney stones

AIM

There is conflicting evidence about the role of obesity in paediatric nephrolithiasis. This Polish study explored the influence of nutritional status and lipid disturbances on urinary lithogenic factors and the risk of kidney stone formation in children and adolescents from three to 18 years of age.

METHODS

We carried out serum lipid profile evaluations and 24-h urine chemistry analyses on 493 overweight/obese paediatric participants (mean age 13 years) without nephrolithiasis and 492 healthy normal weight sex and age-matched controls.

RESULTS

A third (33%) of the study group had blood lipid disturbances, with more acidic urine, lower urinary citrate excretion and a higher fraction of ionised calcium and higher Bonn Risk Index than the controls. The participants' body mass index standard deviation score (BMI Z-score) was positively correlated with urinary oxalate and uric acid and negatively correlated with citrate excretion. Total cholesterol, low-density lipoprotein cholesterol and triglycerides correlated negatively with citraturia, while high-density lipoprotein cholesterol correlated positively.

CONCLUSION

The main factor that predisposed overweight and obese children to kidney stones was hypocitraturia. Urinary citrate excretion was related to both BMI Z-scores and all lipid fraction abnormalities. However, hypercholesterolaemia and particularly low-density lipoprotein hypercholesterolaemia seemed to play a major role.