Prevalence and spot urine risk factors for renal stones in children taking topiramate

Refractory uric acid nephrolithiasis dissolution using phentermine/topiramate: A case report

Uric acid is one of the few kidney stone minerals that can dissolve using oral alkalinization therapies such as potassium citrate. We report an obese female whose recalcitrant uric acid stones were eliminated using the weight loss medication phentermine/topiramate (Qsymia), a metabolic stimulant and carbonic anhydrase inhibitor. Pre- and post-dissolution 24-h urine studies and computed tomography images are included with a proposed mechanism of action of this medication. This is the first description of a non-alkaline oral therapy used alone for uric acid stone dissolution. Additional investigation of this medication in obese or diabetic uric acid stone formers is warranted.

A rise in saliva and urine pH in children with SCN1A-related epilepsy: An exploratory prospective controlled study

Objective

SCN1A, encoding the alpha 1 subunit of the sodium channel, is associated with a range of related epilepsy. This study aims to assess saliva and urine pH in children with SCN1A-related epilepsy.

Methods

A prospective controlled observational study with a 1:1 ratio was conducted on seven patients with SCN1A-related epilepsy and seven healthy children of the same family, gender, and age but without a history of seizures. The pH of saliva and urine was measured by pH test paper. Parents of patients with epilepsy recorded seizures to compare the relationship between pH and seizures.

Results

The fourteen participants were all males, aged 1 to 14 years. Seven patients had different pathogenic SCN1A variants. The pH of saliva and urine was monitored for 21–95 days. The pH of saliva and urine was higher in patients with SCN1A-related epilepsy than in the healthy group. The urine pH in Dravet syndrome patients was high compared with other epilepsy patients. The urine pH in patients with seizures was higher than that in patients without seizures, which occurred during the study.

Conclusions

The pH of saliva and urine was chronically high in patients with SCN1A-related epilepsy, and urine pH was higher in patients with seizures and with Dravet syndrome.

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.

Drug-Induced Urolithiasis in Pediatric Patients

Drug-induced nephrolithiasis is a rare condition in children. The involved drugs may be divided into two different categories according to the mechanism involved in calculi formation. The first one includes poorly soluble drugs that favor the crystallization and calculi formation. The second category includes drugs that enhance calculi formation through their metabolic effects. The diagnosis of these specific calculi depends on a detailed medical history, associated comorbidities and the patient's history of drug consumption. There are several risk factors associated with drug-induced stones, such as high dose of consumed drugs and long duration of treatment. Moreover, there are some specific risk factors, including urinary pH and the amount of fluid consumed by children. There are limited data regarding pediatric lithogenic drugs, and hence, our aim was to perform a comprehensive review of the literature to summarize these drugs and identify the possible mechanisms involved in calculi formation and discuss the management and preventive measures for these calculi.

Incomplete Distal Renal Tubular Acidosis and Kidney Stones

Renal tubular acidosis (RTA) is comprised of a diverse group of congenital or acquired diseases with the common denominator of defective renal acid excretion with protean manifestation, but in adults, recurrent kidney stones and nephrocalcinosis are mainly found in presentation. Calcium phosphate (CaP) stones and nephrocalcinosis are frequently encountered in distal hypokalemic RTA type I. Alkaline urinary pH, hypocitraturia, and, less frequently, hypercalciuria are the tripartite lithogenic factors in distal RTA (dRTA) predisposing to CaP stone formation; the latter 2 are also commonly encountered in other causes of urolithiasis. Although the full blown syndrome is easily diagnosed by conventional clinical criteria, an attenuated forme fruste called incomplete dRTA typically evades clinical testing and is only uncovered by provocative acid-loading challenges. Stone formers (SFs) that cannot acidify urine of pH < 5.3 during acid loading are considered to have incomplete dRTA. However, urinary acidification capacity is not a dichotomous but rather a continuous trait, so incomplete dRTA is not a distinct entity but may be one end of a spectrum. Recent findings suggest that incomplete dRTA can be attributed to heterozygous carriers of hypofunctional V-ATPase. The value of incomplete dRTA diagnosis by provocative testing and genotyping candidate genes is a valuable research tool, but it remains unclear at the moment whether they alter clinical practice and needs further clarification. No randomized controlled trials have been performed in SFs with dRTA or CaP stones, and until such data are available, treatment of CaP stones are centered on reversing the biochemical abnormalities encountered in the metabolic workup. SFs with type I dRTA should receive alkali therapy, preferentially in the form of K-citrate delivered judiciously to treat the chronic acid retention that drives both stone formation and bone disease.

Nephrolithiasis and Nephrocalcinosis From Topiramate Therapy in Children With Epilepsy

Introduction

Adults treated with topiramate may develop nephrolithiasis, but its frequency in children on topiramate is unknown. Topiramate inhibits renal carbonic anhydrase, which can lead to renal tubular acidosis and hypercalciuria. We studied 40 consecutive children who initiated topiramate therapy for seizures between January 1997 and February 2003, followed for a mean of 36 months.

Methods

Serum electrolytes, urinary calcium/creatinine ratios, and renal ultrasonography were performed before topiramate and every 6 months thereafter.

Results

Four children developed nephrolithiasis and/or nephrocalcinosis, which resolved on discontinuation of topiramate. In 40 patients, the mean urinary calcium/creatinine ratio increased over time (P < 0.001). The mean serum bicarbonate in 40 patients decreased over time (P < 0.01). Twenty-three children had urinary calcium/creatinine ratios before topiramate. Nine children with baseline hypercalciuria (defined as urinary calcium/creatinine >0.21) were compared with the 14 children with baseline normal urinary calcium excretion. A greater increase in urinary calcium/creatinine ratios occurred in hypercalciuric children (P < 0.001) and a greater decrease in serum bicarbonate levels occurred in the hypercalciuric children (P < 0.05) compared with children with baseline normal calcium excretion. Greater urinary calcium excretion was associated with increasing doses of topiramate (P = 0.039).

Conclusion

Our study shows that long-term therapy with topiramate in children is associated with persistent hypercalciuria and metabolic acidosis, which can lead to nephrocalcinosis and/or nephrolithiasis. All children initiating topiramate therapy should have baseline and follow-up urinary calcium/creatinine studies, serum electrolytes, and periodic renal ultrasonography, if the urinary calcium/creatinine ratio increases to a level above normal for age.

Drug-Induced Kidney Stones and Crystalline Nephropathy: Pathophysiology, Prevention and Treatment

Drug-induced calculi represent 1-2% of all renal calculi. The drugs reported to produce calculi may be divided into two groups. The first one includes poorly soluble drugs with high urine excretion that favour crystallisation in the urine. Among them, drugs used for the treatment of patients with human immunodeficiency, namely atazanavir and other protease inhibitors, and sulphadiazine used for the treatment of cerebral toxoplasmosis, are the most frequent causes. Besides these drugs, about 20 other molecules may induce nephrolithiasis, such as ceftriaxone or ephedrine-containing preparations in subjects receiving high doses or long-term treatment. Calculi analysis by physical methods including infrared spectroscopy or X-ray diffraction is needed to demonstrate the presence of the drug or its metabolites within the calculi. Some drugs may also provoke heavy intra-tubular crystal precipitation causing acute renal failure. Here, the identification of crystalluria or crystals within the kidney tissue in the case of renal biopsy is of major diagnostic value. The second group includes drugs that provoke the formation of urinary calculi as a consequence of their metabolic effects on urinary pH and/or the excretion of calcium, phosphate, oxalate, citrate, uric acid or other purines. Among such metabolically induced calculi are those formed in patients taking uncontrolled calcium/vitamin D supplements, or being treated with carbonic anhydrase inhibitors such as acetazolamide or topiramate. Here, diagnosis relies on a careful clinical inquiry to differentiate between common calculi and metabolically induced calculi, of which the incidence is probably underestimated. Specific patient-dependent risk factors also exist in relation to urine pH, volume of diuresis and other factors, thus providing a basis for preventive or curative measures against stone formation.

Endemic bladder calculi in children

Urinary calculi are being recognized more frequently in children and the urinary bladder is the most common site for stone formation in the lower urinary tract. Bladder calculi are grouped into three basic categories: primary idiopathic/endemic, secondary, and migrant. The incidence of vesical calculi has declined significantly in the last 70 years in developed nations owing to improvements in nutrition and socioeconomic conditions, but it is still high in developing nations. Primary idiopathic/endemic bladder calculi typically occur in children, in the absence of urinary tract infection (UTI), urinary stasis, or foreign body, and diet lacking in animal proteins is the major contributor factor. Comprehensive preventive and treatment strategies are critical for improving the quality of life of diseased children, in addition to helping to eradicate, or at least decrease, the incidence of endemic bladder calculi in developing nations.

The effect of antiepileptic drugs on the kidney function and structure

INTRODUCTION

Long-term use of antiepileptic drugs (AEDs) is associated with number of somatic conditions. Data from experimental, cross-sectional and prospective studies have evidence for the deleterious effect of some AEDs on the kidney. Areas covered: This review summarized the current knowledge of the effect of AEDs on the kidney including evidence and mechanisms. Fanconi syndrome was reported with valproate (VPA) therapy in severely disabled children with epilepsy. Renal tubular acidosis and urolithiasis were reported with acetazolamide, topirmate and zonisamide, drugs with carbonic anhydrase inhibition properties. Increased levels of urinary N-acetyl-beta-D-glucosaminidase (NAG) to urinary creatinine (U-NAG/UCr), urinary excretion of α1-micrglobulin, β-galactosidase activity; and urinary malondialdehyde to creatinine (MDA/Cr), markers of renal glomerular and tubular injury, were reported with chronic use of some AEDs (VPA, carbamazepine and phenytoin). The mechanism(s) of kidney dysfunction/injury induced by AEDs is unknown. Experimental and clinical studies have shown that VPA induces oxidative stress, mitochondrial deficits, carnitine deficiency and inflammation and fibrosis in renal tissue in mice and in vitro studies. Expert commentary: It seems reasonable to monitor kidney function during treating patients with epilepsy at high risk of kidney injury (e.g. on combined therapy with more than one AED, severely disabled children, etc).

Use of Ultrasound in Pediatric Renal Stone Diagnosis and Surgery

Pediatric urolithiasis is on the rise globally and incidence rates have risen by 6-10% annually over the past couple of decades. Given the increasing incidence, high likelihood of recurrence, and long life expectancy of children, the use of ionizing radiation in the diagnosis, management, and follow up of pediatric urolithiasis has been scrutinized recently and many institutions and organizations have emphasized the use of non-ionizing imaging modality such as ultrasound. This review examines the use of ultrasound in the diagnosis and treatment of pediatric urolithiasis. Specifically, the role of ultrasound in shockwave lithotripsy, percutaneous nephrolithotomy, and, more recently, ureteroscopy will be examined.

Trends in pediatric urolithiasis: patient characteristics, associated diagnoses, and financial burden

BACKGROUND

The goal of this study was to examine national trends in hospitalization, emergency department (ED) utilization, secondary diagnoses, and charges associated with pediatric urolithiasis.

METHODS

Data were evaluated from the Kids' Inpatient Database of the Healthcare Costs and Utilization Project (HCUP) database from 1997 to 2012 and the HCUP National ED Sample from 2006 to 2011.

RESULTS

Pediatric nephrolithiasis discharges increased by 18%, while ureterolithiasis discharges decreased by 17%. Hospital charges increased by 20% when accounting for inflation, despite an overall decrease in discharges by 2.5%. Female patients and those aged 15-17 years were more commonly affected. Pediatric ED visits increased by 9%. The most common secondary diagnoses during 2003-2009 were urinary tract infections (UTI) (13%), asthma (9%), epilepsy (4%), and paralysis (4%).

CONCLUSIONS

Decreased hospitalizations and increased ED visits indicate a shift to outpatient care. Inpatient health care charges associated with pediatric urolithiasis continue to rise. Comorbidities include UTI, asthma, epilepsy, attention deficit hyperactivity disorder (ADHD), and mood disorders. Because of the significant health care burden and the increased risk to children of developing long-term sequelae there is a strong need for increased research into the mechanism of this systemic inflammatory disease and improved therapeutic targets.