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

Diagnosis and Management of Nephrolithiasis in Children

The incidence of kidney stones in children is increasing. Approximately two-thirds of pediatric cases have a predisposing cause. Children with recurrent kidney stones have an increased higher risk of developing chronic kidney. A complete metabolic workup should be performed. Ultrasound examination is the initial imaging modality recommended for all children with suspected nephrolithiasis. A general dietary recommendation includes high fluid consumption, dietary salt restriction, and increased intake of vegetables and fruits. Depending on size and location of the stone, surgical intervention may be necessary. Multidisciplinary management is key to successful treatment and prevention.

Evaluation of urinary acidification in children: Clinical utility

The kidney plays a fundamental role in acid-base homeostasis by reabsorbing the filtered bicarbonate and by generating new bicarbonate, to replace that consumed in the buffering of non-volatile acids, a process that leads to the acidification of urine and the excretion of ammonium (NH₄ ⁺). Therefore, urine pH (UpH) and urinary NH₄ ⁺ (UNH₄ ⁺) are valuable parameters to assess urinary acidification. The adaptation of automated plasma NH₄ ⁺ quantification methods to measure UNH₄ ⁺ has proven to be an accurate and feasible technique, with diverse potential indications in clinical practice. Recently, reference values for spot urine NH₄ ⁺/creatinine ratio in children have been published. UpH and UNH₄ ⁺, aside from their classical application in the study of metabolic acidosis, have shown to be useful in the identification of incomplete distal renal tubular acidosis (dRTA), an acidification disorder, without overt metabolic acidosis, extensively described in adults, and barely known in children, in whom it has been found to be associated to hypocitraturia, congenital kidney abnormalities and growth impairment. In addition, a low UNH₄ ⁺ in chronic kidney disease (CKD) is a risk factor for glomerular filtration decay and mortality in adults, even in the absence of overt metabolic acidosis. We here emphasize on the need of measuring UpH and UNH₄ ⁺ in pediatric population, establishing reference values, as well as exploring their application in metabolic acidosis, CKD and disorders associated with incomplete dRTA, including growth retardation of unknown cause.

24-Hour urine collection for first time pediatric stone formers: Is it worth it?

INTRODUCTION/OBJECTIVE

24-h urine collections are recommended for motivated first-time stone formers. Given that children have a lifetime potential for recurrences, metabolic work-up has been recommended. 24-hour urine collections can be problematic, especially in children. We sought to study the benefits of 24-h urine collections in children with stones.

STUDY DESIGN

We performed a single center, retrospective chart review of the most recent pediatric nephrolithiasis patients under age 18 at our center who supplied their first 24-h urine collection. We assessed whether 24-h urine results led to a change in management and if those patients were adherent to the recommendations.

RESULTS

Seventy pediatric nephrolithiasis patients who had 24-h urine collection were reviewed. Recommendations other than standard dietary and fluid intake changes were made in 8/70 (11%). A low citrate/calcium ratio (327 vs. 525, p < 0.03) and whether the test was ordered by nephrology vs. urology (26% vs. 2%, p < 0.003) were predictive of an additional recommendation. Of the 8 patients who had changes recommended only 1/8 completed a repeat 24-h urine collection, 3/8 never returned for followed up and 2/8 stopped the medicines prior to follow up. There was no difference in early stone recurrence rates, 55% of the studies were incorrectly collected, and total costs are estimated at $9800.

DISCUSSION

Our study aimed to evaluate the impact and value of 24-h urine collection in first time pediatric stone formers. We found that 24-h urine collections altered management from standard dietary recommendations in only 11% of cases. These collections were fraught with challenges - 55% of our samples appeared to be incorrectly collected, there was at least one abnormality noted in 100% of collections, these tests are expensive, and patients were poorly compliant with recommendations based on test results. Additionally, changes made based on the 24-h urine results seemed to vary depending on who evaluated the test results. Among cases in which changes were made, nephrologists made alterations at a far greater rate than urologists did. We do acknowledge there are several limitations to our study. First, this is a retrospective chart review. Second, for the urology patients, we were only able to review patient records that were available due to a transition from one electronic medical record to another, resulting in a loss of some earlier patient records. We highly doubt that those records we could not review were significantly different than those we did review. Third, this is a single center design and includes the practice patterns of the providers here. We acknowledge that our local practice patterns may or may not be reflective of national practice patterns, however, most clinicians are likely faced with similar interpretation issues and poor rates of compliance and could benefit from guidelines.

CONCLUSION

24-h urine collection for first time pediatric stone formers is expensive, difficult to accomplish and infrequently leads to treatment changes. Our data suggest it adds little for most children with stones and may be better reserved for those children with recurrent stone disease.

Analysis of urine composition from split 24-h samples: use of 12-h overnight samples to evaluate risk factors for calcium stones in healthy and stone-forming children

INTRODUCTION

The analysis of 24-h urine is the gold standard to diagnose metabolic abnormalities in the stone-forming patient. However, urinary composition changes throughout the day and analyzing the whole 24-h urine may mask peaks of increased risk of crystallization.

OBJECTIVE

To examine variations of stone-promoting and stone-inhibiting factors in urine using split 24-h samples from healthy and stone-forming children.

STUDY DESIGN

Urine was collected from 87 healthy and 26 stone-forming children using a split collection procedure (12-h daytime urine and 12-h overnight urine). Urine volume, pH, calcium (Ca), magnesium (Mg), phosphate (P), citrate (Cit), uric acid (Ur), and oxalate (Ox) were determined, and the Ca/Cit ratio was calculated.

RESULTS

The overnight urine samples in both groups had higher levels of P and Mg, lower volume, lower pH, and less citrate and uric acid. As can be seen in the table, higher percentages of healthy and stone-forming children had altered 12-h night urine than 24-h urine with regards to Ca/Cr, Cit/Cr and Ca/Cit ratios. All healthy subjects and all stone-forming children (except one) with altered Cit/Cr ratios or Ca/Cit ratios in the 24-h sample also had altered ratios in the 12-h overnight sample.

DISCUSSION

This study indicates that urine composition changes throughout the day, and that there is daily variability in most of the parameters related to kidney stone formation. Furthermore, 12-h overnight samples seem to be more sensitive than 24-h samples in detecting the most common urinary abnormalities. The main limitation of this study is the relative low sample size of stone-forming children, owing to the low prevalence of nephrolithiasis in childhood.

CONCLUSIONS

We observed a higher excretion of stone-promoting substances and a lower citrate in urine at night. However, the study results do not provide enough evidence to conclude that the use of a 12-h overnight sample collection can replace 24 h urine analysis in the metabolic evaluation of children with lithiasis.

Incidence of kidney stone disease in Icelandic children and adolescents from 1985 to 2013: results of a nationwide study

BACKGROUND

An increase in the incidence of kidney stone disease has been reported for all age groups worldwide. To examine this trend, we conducted a nationwide study of the epidemiology of kidney stones in Icelandic children and adolescents over a 30-year period.

METHODS

Computerized databases of all major hospitals and medical imaging centers in Iceland were searched for International Classification of Diseases and radiologic and surgical procedure codes indicative of kidney stones in patients aged < 18 years, followed by a thorough medical record review. Age-adjusted incidence was calculated for the time intervals 1985-1989, 1990-1994, 1995-1999, 2000-2004, 2005-2009, and 2010-2013. Time trends in stone incidence were assessed by Poisson regression. The prevalence of stone disease for the years 1999-2013 was also determined.

RESULTS

Almost all the 190 patients (97%) that we identified had symptomatic stones, and acute flank or abdominal pain and hematuria were the most common presenting features. The total annual incidence of kidney stones increased from 3.7/100,000 in the first 5-year interval to 11.0/100,000 during the years 1995-2004 (p < 0.001) and decreased thereafter to 8.7/100,000 in 2010-2013 (p = 0.63). The incidence rise was highest in girls aged 13-17 years, in whom it rose from 9.8/100,000 in 1985-1989 to 39.2/100,000 in 2010-2013 (p < 0.001), resulting in an overall female predominance in this age group. The mean annual prevalence of stone disease in 1999-2013 was 48/100,000 for boys and 52/100,000 for girls.

CONCLUSION

We found a significant increase in the incidence of childhood kidney stone disease, driven by a dramatic increase of stone frequency in teenage females which is poorly understood and warrants further study.

Urinary stone risk factors in the descendants of patients with kidney stone disease

BACKGROUND

Evidence has indicated that immediate family members of nephrolithiasis patients had high opportunity to develop stones. However, they are usually not regarded to be at risk, since it is unclear if there are any lithogenic abnormalities found in non-stone-forming nephrolithiasis relatives. Our aim was to investigate urinary metabolic abnormalities in the children of nephrolithiasis patients, compared with the general population.

METHODS

The 24-h urinary metabolic profile was studied for 28 calcium oxalate nephrolithiasis patients (NL) and 46 of their descendants (ND), as well as 40 non-stone-forming volunteers (V) and 34 of their descendants (VD).

RESULTS

There was no difference between age, gender, and serum creatinine between NL vs. V (parental groups) and ND vs. VD (descendant groups). High urinary oxalate in nephrolithiasis and urinary calcium in their descendants was detected. In addition, an elevated urinary excretion rate of calcium, phosphate, protein, and albumin, along with low citrate excretion and high urinary supersaturation was observed in both the nephrolithiasis patients and their descendants. Approximate 17.8-24.4% of the nephrolithiasis descendants had a urinary supersaturation higher than the nephrolithiasis level, but none was found in VD group. The level of urinary supersaturation index was correlated with urinary protein and albumin excretion in nephrolithiasis family.

CONCLUSION

It was demonstrated that nephrolithiasis offspring carried several urinary metabolic risks predisposing to stone formation which are similar to their parents, and about one in every five nephrolithiasis children had nephrolithiasis level urinary supersaturation.

What do we know about pediatric renal microlithiasis?

Renal or calyceal microlithiasis is a common disorder with increasing prevalence especially in infants and younger children. The main presenting symptoms and the underlying metabolic abnormalities of renal microlithiasis are similar to renal stone. Although renal microlithiasis is considered as a main problem of the health system with diverse etiologies, our information about its natural course is very limited. Hence, further investigations to make an appropriate clinical approach to this entity is mandatory. Also, general practitioners, pediatricians, nephrologists and urologists have to be well educated regarding renal microlithiasis for early diagnosis, appropriate evaluation and proper management of this entity. In this review study, we focused on collection of the present information about different aspects of renal microlithiasis in children.

Co-Occurrence of Asthma and Nephrolithiasis in Children

It has been proposed that epithelial dysfunction and inflammation may predispose patients to kidney stone formation. Asthma is another chronic condition related to epithelial dysfunction and inflammation. We hypothesized that pediatric patients with asthma would have an increased prevalence of nephrolithiasis. Furthermore, we investigated if asthma patients with nephrolithiasis have clinical characteristics and urine profiles that point to mechanisms of stone formation. We evaluated 865 pediatric patients who had a diagnosis of nephrolithiasis. Clinical/demographic data and 24 hour urine samples were compared between asthma + stone (n = 142) and stone only patients. Data from asthmatics without stone were also available for evaluation of medication differences among asthma + stone and asthma only patients. The prevalence of nephrolithiasis in the pediatric population at our institution was 0.08% vs. 0.31% in our pediatric asthmatic population. The prevalence of asthma in our pediatric population was 6.8% vs. 26.7% in our pediatric stone patients. Asthma + stone patients were more likely to be on a combination inhaled corticosteroid + long acting beta agonist inhaler as compared to age/gender/BMI matched asthma patients without stone (29.7% vs. 13.7%, p = 0.0012). 259 kidney stone patients had 24 hour urine samples for comparison. There was no difference in 24 hour urine profiles between asthma + stone and stone only patients. Children with asthma have a 4-fold greater prevalence of kidney stones than the general pediatric population. Similarly, children with kidney stones have a 4-fold greater prevalence of asthma. This correlation may suggest a mechanistic link between asthma and nephrolithiasis. Further investigation is needed to elucidate the pathophysiologic origin of this relationship.

National multi-institutional cooperative on urolithiasis in children: Age is a significant predictor of urine abnormalities

INTRODUCTION

Pediatric nephrolithiasis is a growing problem and prior studies have shown the greatest increase in nephrolithiasis in the adolescent population. Metabolic abnormalities have historically been cited as the primary cause of pediatric nephrolithiasis; however, dietary and other factors such as obesity have also been studied with mixed results.

OBJECTIVE

We reviewed the charts of pediatric patients with a history of nephrolithiasis to determine the number and types of metabolic abnormalities present on 24-h urine analysis.

STUDY DESIGN

We retrospectively reviewed the charts of all pediatric patients with a history of nephrolithiasis from 1999-2013 across four different institutions. The subjects were excluded if they had a history of spina bifida, neurogenic bladder, cerebral palsy, isolated bladder stones, or if they were on medical therapy for nephrolithiasis before the first 24-h urine collection.

RESULTS

There were 206 subjects included in the analysis with an average age of 13 (±3.9) years. The patients were stratified into two age groups based on an apparent bimodal distribution of metabolic abnormalities, ≤10 years and >10 years of age. Metabolic abnormalities were present in 130 children (63.1%) and there was a difference between the groups, with children ≤10 years more likely to have a metabolic abnormality compared with those >10 years of age (75% vs. 60.6%, p = 0.0443) on univariate analysis. In children ≤10 years hypercalciuria was the most common disorder present (48.4%), and in children >10 years hypocitraturia was the most common disorder present (26.1%). Children ≤10 years of age were more likely to have normal volume (p = 0.006), elevated urinary oxalate (p = 0.0351), elevated urinary calcium (p < 0.001), elevated supersaturation of calcium phosphate (p < 0.001), and elevated supersaturation of calcium oxalate (p = 0.002). On multivariate analysis, children ≤10 years of age were more likely to have normal volume, hyperoxaluria, elevated supersaturation of calcium phosphate and a trend towards hypercalciuria (Table).

DISCUSSION

Our study reveals that younger children are more likely to have a metabolic abnormality present on 24-h urine analysis. This has important implications when deciding on treatment options, with younger children potentially requiring more aggressive management with medical therapy. Older children were more likely to have low urinary volume and their most common metabolic abnormality was hypocitraturia. Although dietary factors have not been established as the definitive reason behind the rising incidence of nephrolithiasis in the adolescent population, older children may benefit more from diet modification with a strong focus on increasing volume intake.

CONCLUSION

We found differences in younger compared with older age groups in terms of the number and types of metabolic disorders present. Children ≤10 years of age were more likely to have a metabolic disorder including elevations in calcium, oxalate and supersaturation of calcium phosphate, while children >10 years of age were more likely to have low urinary volume. These differences have important implications for future investigative studies on the rising incidence as well as the best course of treatment for children with nephrolithiasis.

The evolving epidemiology of stone disease

The epidemiology of kidney stones is evolving – not only is the prevalence increasing, but also the gender gap has narrowed. What drives these changes? Diet, obesity or environmental factors? This article will review the possible explanations for a shift in the epidemiology, with the hope of gaining a better understanding of the extent to which modifiable risk factors play a role on stone formation and what measures may be undertaken for disease prevention in view of these changing trends.

The effect of prophylactic treatment with Shohl's solution in children with cystinuria

OBJECTIVE

To investigate the effect of prophylactic treatment with Shohl's solution on the rates of stone recurrence in paediatric patients with cystinuria.

PATIENTS AND METHODS

Between June 2007 and October 2011, 185 patients aged 16 years and younger whose stones had been completely removed by percutaneous nephrolithotomy (PCNL) were assessed for metabolic risk factors. Seventeen (9%) patients with positive cyanide-nitroprusside tests (CNT) and cystine stones enrolled in this study, and a Shohl's solution was used for alkalinisation. The patients were followed up for a mean period of two years for stone recurrence.

RESULTS

Of the patients, 10 (59%) were male, and 7 (41%) were female (p = 0.13). Twelve patients (70.5%) continued to receive medical prophylaxis regularly, whereas 5 (29.5%) patients did not. The mean pre-treatment and post-treatment urinary pH values were 5.8 ± 0.5 (5-7) and 7.5 ± 0.4 (6.5-8), respectively (p < 0.001). The pre-treatment and post-treatment specific gravities of the urine were 1021.5 ± 5.4 (1010-1030) and 1006 ± 2.3 (1004-1015), respectively (p < 0.001). The rates of recurrence were 16.6% among those who continued prophylaxis and 100% among those who did not receive prophylaxis (p = 0.001). The most common combination of metabolic anomalies was cystinuria and hypocitraturia (p < 0.001).

CONCLUSIONS

This study demonstrated that detailed clinical and laboratory evaluations should be performed for all children with cystine stone disease, and, appropriate prophylactic treatment should be recommended to prevent the reformation of stones.

High recurrence rate at 5-year followup in children after upper urinary tract stone surgery

PURPOSE

Pediatric urolithiasis has been treated with shock wave lithotripsy, ureteroscopy and percutaneous nephrolithotomy with high success rates during short-term followup. We studied our success rate and modifiable risk factors in patients with at least 5 years of followup postoperatively.

MATERIALS AND METHODS

Retrospective chart review was performed for patients younger than 18 years who underwent upper tract stone surgery between 1999 and 2007, were stone-free afterward and had at least 5 years of followup. Recurrence rate, and anatomical and metabolic abnormalities were assessed.

RESULTS

Of 60 eligible children 30 (33 kidneys) had at least 5 years of followup. Average patient age at surgery was 10 years, 17 patients were female and 20 kidneys had anatomical abnormalities. Overall recurrence rate at 5 years was 55% (95% CI 38%-70%). Ureteral stones had a lower recurrence rate than renal stones (5 of 19 and 13 of 14, respectively, p <0.001). Patients with abnormal anatomy had a 65% (95% CI 43%-82%) chance of recurrence within 5 years vs 38% (95% CI 18%-65%) in those with normal anatomy (p = 0.17). Of the 18 recurrences 10 required a second operation, 7 demonstrated abnormal anatomy and 14 involved calcium based stones. A 24-hour urine test in 13 children revealed 10 with hypercalciuria and 11 with hypocitraturia, with 9 patients exhibiting both conditions.

CONCLUSIONS

We found a high recurrence rate in children with stones requiring surgical intervention, particularly those with abnormal anatomy. This finding should be confirmed in a larger multicenter study of recurrence rates. In the meantime our results suggest a need for aggressive diagnosis and treatment of metabolic abnormalities.

Changing stone composition profile of children with nephrolithiasis

OBJECTIVE

To determine if this trend toward calcium phosphate stone formation exists in children.

METHODS

This is a retrospective study of medical records of 179 children managed at our medical center from 1992-2010 for whom stone analysis and other pertinent laboratory data were available. A comparison of patients managed from 1992-2000 (P1) and 2001-2010 (P2) was undertaken. Statistical analysis included nonparametric tests.

RESULTS

There were no significant differences in the mean age of the 2 cohorts. During both periods, boys comprised a significantly higher proportion during the first decade of life, whereas girls comprised a significantly higher proportion during the second decade. A higher percentage of patients had calcium oxalate (CaOx) stones in P1 compared to P2 (60% vs 47%, P = .0019). There was a significant increase in the percentage of patients having calcium phosphate stones in P2 compared to P1 (27% vs 18.5%, P = .008). Twenty-seven patients had recurrent stones. A comparison of the compositions of the first and last stones of patients within this group demonstrated an increasing proportion of brushite stones (3.7% vs 11.1%, P = .04). Twenty-four hour urine testing results were similar for those with CaOx and calcium phosphate stones.

CONCLUSION

An increasing proportion of children have calcium phosphate calculi. Brushite stones are more prevalent in children with recurrent stone events. The impetus of these shifts is not readily apparent.

Metabolic risk factors and the effect of metaphylaxis in pediatric stone disease with hypocitraturia

To describe the metabolic risk factors and investigate the effect of prophylaxis based on these factors on long-term recurrence of urolithiasis in pediatric patients with hypocitraturia. One-hundred and twenty-nine pediatric patients who underwent percutaneous nephrolithotomy between January 2008 and June 2011 were evaluated for metabolic risk factors. The patients with hypocitraturia were enrolled in this study and the data were analyzed using statistical methods for a mean period of 2 years for metabolic abnormalities, stone type, and the effect of potassium citrate prophylaxis on stone recurrence. A 24-h urine metabolite analysis revealed one or more metabolic risk factors in 115 (89.2 %) of the patients, whereas 14 (10.8 %) of the patients had no metabolic abnormalities. Eighty-two (63.5 %) of 129 patients had hypocitraturia. Of them, 43 (52 %) were male and 39 (48 %) were female, with a mean age of 9.7 ± 4.9 and 6.7 ± 4.4 (1-16) years, respectively(p = 0.102). Thirty-five (42.7 %) had pure hypocitraturia, and 47 (57.3 %) had two or more metabolic abnormalities. The most common dual metabolic abnormality was hypocitraturia and hypomagnesuria. Seventy-one patients (87 %) with hypocitraturia received medical prophylaxis and continued regularly, whereas 11 (13 %) patients did not receive medical prophylaxis despite being advised to do so. After a mean follow-up of 26.5 ± 9.4 months, the rate of recurrence was 1.4 % in the patients with hypocitraturia who continued prophylaxis and occurred in all of the patients who did not receive prophylaxis (p < 0.001). Calcium oxalate stones (95.2 %) were the most commonly found stones in the stone analysis. Detailed clinical and laboratory evaluations should be performed in children with urolithiasis. Appropriate prophylactic treatment as potassium citrate, should be given to prevent reformation of stones in patient with hypocitraturia.