Pediatric urolithiasis: metabolic risk factors and follow-up results in a Turkish region with endemic stone disease

Three-channel ion chromatograph for improved metabolic evaluation of urolithiasis

Background

Urolithiasis is a multi-etiological disease resulting from a combination of environmental and genetic factors. One of the most challenging aspects of this disease is its high recurrence rate. For most patients, an in-depth metabolic evaluation may reveal the presence of urinary stones. The fact that different urinary stone-related compounds (USRCs) are measured by different methods renders the metabolic evaluation of urolithiasis quite tedious and complex.

Methods

A three-channel ion chromatograph (IC) that automatically measures the concentration of common metabolic indicators of urolithiasis in urine (i.e., oxalate, citrate, uric acid, calcium, and magnesium) was developed to improve the efficiency. To validate its precision and specificity, standard curves were prepared using working solution of these indicators. 100 standard solutions of these indicators were measured with our new IC and three other ICs as the control instruments; analyte concentrations in 100 24-h urine samples from volunteers and 135 calculi patients were also measured.

Results

All analytes had good linear relationships in concentration ranges of 0–10 mg/L. The precision experiments in the standard and urine samples showed that the measurement errors of the newly developed IC were all less than 5%. In urine, the recovery rate ranged from 99.6 to 100.4%, the coefficient of variation ranged from 1.39 to 2.99%, and the results matched between our newly developed IC and the control ICs. The results of the efficiency test showed that we can finish the analysis at the average number of 14 people per day with the new IC. While the average number in the control group is 3.85/day (p = 0.000).

Conclusions

Overall, this multi-channel system significantly improves the efficiency of metabolic evaluation while retaining accuracy and precision.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12894-021-00914-4.

Is medical treatment necessary for infants with small urinary stones?

Urinary stone disease is a common condition. We investigated the usefulness of medical treatment for infants with urinary stones 5 mm or smaller. The study included 197 infants (86 girls and 111 boys) with urolithiasis ≤ 5 mm who were referred to our Department of Nephrology between 2014 and 2016. Infants with metabolic or anatomical risk factors requiring medical treatment were excluded from the study. We retrospectively reviewed urine and serum metabolic profiles and compared stone resolution rates in patients who did and did not receive treatment. The mean age at diagnosis was 5.2 months (range, 14 days to 12 months). The most common complaint was restlessness (n = 92, 46.7%), and 49 infants (24.9%) were asymptomatic. Multiple stones were detected in 166 infants (84.3%). Hypomagnesuria, hypocitraturia, and hypercalciuria were present in 25.3, 19.7, and 18.7% of patients, respectively. Stones < 3 mm (microlithiasis) were detected in 97 infants (49.2%), and 100 (50.8%) patients had 3-5 mm stones. In total, 130 infants (66.5%) received regular treatment and 67 (33.5%) were not treated. Stone resolution was significantly higher in the group receiving K-citrate treatment at the 6th month follow-up, while there were no significantly difference between the two groups at the 12th month control. No previous studies have investigated treatment outcomes in infants with 3-5 mm urinary stones. According to our results, K-citrate treatment may accelerate the resolution of the stone in infants with stones smaller than 5 mm.

Characteristics of infant urolithiasis: A single center experience in western Turkey

INTRODUCTION

Urolithiasis (UL) in infancy has different incidence, etiology, presentation and course compared to UL in childhood and in adults. We evaluated the clinical, radiological, metabolic factors and course of infant UL in western Turkey.

METHODS

Medical records of the infants between 1 and 12 months of age with a diagnosis of UL were reviewed retrospectively for gender, gestational age, age at diagnosis, presenting symptoms, past medical history, parental consanguinity, family history of UL, urinary tract abnormalities, urinary tract infections, localization-size-number of stones, course of stones, treatment modality of UL (medical vs surgical) and follow up duration. Patients were grouped as those who did not require surgical intervention (Group 1) and those who underwent any kind of stone surgery (Group 2). Both groups were compared for the study parameters.

RESULTS

There were 80 infants (48 males) with a mean age of 6.0 ± 2.9 months at diagnosis. Mean follow-up duration was 29.7 ± 23.1 months. Two thirds of the patients presented with symptoms/signs not directly related to urinary system. Predisposing factors included metabolic abnormalities in 24 (30%) patients and urinary tract malformations in 9 (11%) patients. Group 1 (n = 58) and Group 2 (n = 22) were not different with respect to the study parameters except for the larger stone size and higher rate of hyperuricosuria in Group 2. Stone size of 4.5 mm has a 72.7% sensitivity and 74.1% specificity for predicting surgical intervention. Infants treated medically and those followed by hydration only did not differ for regression rate of stones and for requirement for surgical intervention. However, metabolic abnormalities were significantly higher in medically treated infants.

CONCLUSION

Every infant with urolithiasis should be evaluated for risk factors. Modification of such predisposing factors when possible may mitigate the notably high recurrence rate of UL in children. Increased awareness of infant UL may allow for earlier detection, improved evaluation and follow up, and may thereby decrease the morbidity of the disease.

What predicts spontaneous passage of ≤1 cm ureteral stones in children?

PURPOSE

The aim of this study is to determine what factors predict spontaneous passage of ≤1 cm ureteral stones in children.

METHODS

Files of the patients diagnosed with a single ureteral stone on a given side between 2008 and 2017 were retrospectively reviewed. Patients with congenital obstructive uropathy, neurogenic bladder, vesicoureteral reflux and those with a stone diameter of >1 cm were excluded. Detection of ureteral stones was done using ultrasonography (US) primarily, and computed tomography when US findings were inconclusive. Patients were treated either conservatively or surgically. Conservative treatment included adequate hydration and pain management whereas surgical treatment included ureteroscopic intervention. Apart from those who required urgent intervention, patients were referred for surgical treatment after 2-4 weeks of follow-up with no spontaneous passage. Factors analyzed for association of spontaneous passage included age, gender, type of hematuria, stone localization, laterality, presence of concomitant kidney stone, degree of hydronephrosis, stone size and stone composition.

RESULTS

A total of 70 patients (38 males, 32 females); median age 4.7 years had a ≤ 1 cm ureteral stone (median diameter 7 mm). US was able to diagnose the ureteric stone in 47 patients while computed tomography was required in 23 patients. Spontaneous passage was observed in 40 patients (57.1%). Median time for stone passage was 8 days (3-34 days). Stone size and presence of hematuria (macroscopic and microscopic combined) were factors associated with spontaneous passage and 6.7 mm was found to be the cut-off (AUC = 0.953; 95% CI 0.905-1.000; sensitivity 96.7%, specificity 82.5%, p < 0.001). Moreover, age, degree of hydronephrosis or stone location were not associated with spontaneous passage.

CONCLUSION

Patients with a ureteric stone size <6.7 mm can safely be followed conservatively, with a spontaneous passage rate of 82.5%. Type of Study Case series with no comparison group. Level of Evidence IV.

Evaluation of the composition of urinary tract stones in children from the Inner Western Anatolian Region in Turkey

OBJECTIVE

Pediatric urolithiasis is a globally growing problem. The composition and frequency of urinary tract stones vary not only among different countries, but across various regions in a country. Hence, we aimed to identify the types and frequencies of urinary tract stones in children from our region (Inner Western Anatolian part of Turkey), and to compare our findings with the results from other regions in our country.

MATERIAL AND METHODS

In this retrospective analysis of 53 pediatric urolithiasis cases that were treated in our hospital between 2009 and 2019, the demographic data, clinical course, radiological and metabolic findings, the recurrence rate, and the composition of the stones were evaluated.

RESULTS

The mean age of the patients was 5.9±4.6 (0.5-18) years, and there were 30 (56.6%) girls and 23 (43.4%) boys. An analysis of the composition of the stones revealed that the majority (85%) consisted of calcium oxalate. The highest risk of recurrence and the need for multiple shockwave lithotripsy (SWL) sessions or surgical intervention appeared to be related with the presence of whewellite stones, which are the most challenging stones in childhood.

CONCLUSION

According the study results, the urinary stone types vary across different regions in our country, and the frequency of uric acid stones decreased going westward, while the frequency of oxalate stones increased. We conclude that this difference in the frequency of the type of urinary stones might reflect the regional dietary habits. Regional frequency and etiology studies for the types of urolithiasis may facilitate the approach to the treatment of urolithiasis.

Pediatric calculi: cause, prevention and medical management

PURPOSE OF REVIEW

The incidence of pediatric nephrolithiasis is on the rise, with a significant related morbidity and a concomitant relevant increase in healthcare costs. The purpose of this review is to portray the current epidemiology and cause of renal stones in children, to provide a framework for appropriate clinical evaluation on an individual basis, and a guidance regarding treatment and prevention for the significant risk of lifelong recurrence and deriving complications.

RECENT FINDINGS

The early identification of modifiable risk factors and other abnormalities is essential, to prevent related morbidity, the onset of chronic kidney disease, and the associated increased risk of developing other diseases. The implementation of risk reduction strategies, including dietary modifications and targeted pharmacological therapies, will significantly influence stone recurrences and preserve renal function.

SUMMARY

Future research is desirable, with the aim to strengthen personalized conservative management of pediatric nephrolithiasis as first-line treatment.

Protective effect of salvianolic acid B against oxidative injury associated with cystine stone formation

The aim of this study was to investigate the role of oxidative stress in cystine crystal formation and whether salvianolic acid B, a natural antioxidant, could prevent cystine-mediated oxidative injury in vivo and in vitro. The levels of oxidative stress and antioxidase activity in cystine stone patients were assessed. Then, the oxidative stress exerted by cystine on human kidney-2 (HK-2) cell viability and biochemical parameters including antioxidase activity and antioxidant protein expression were evaluated, and the protective action of salvianolic acid B was also examined. Finally, salvianolic acid B was tested to determine whether it could prevent or reduce renal crystal formation in Slc7a9 knockout mice. The activity levels of superoxide dismutase (SOD) and glutathione peroxidase (GPx) were decreased, and the amount of malondialdehyde (MDA) was increased in patients with cystine stones compared with people without cystine stones (p < 0.05). Significant reductions in cell viability, antioxidase activity and antioxidant protein expression levels were found in the cystine group compared with controls. However, such oxidative injuries were prevented by salvianolic acid B. In the animal study, loose crystals with white spots were seen in the renal parenchyma, bilateral renal pelvis and bladders in the Slc7a9 knockout group. In contrast, no renal crystals were seen in the control group, and markedly fewer crystals with significantly higher antioxidase activity and diminished oxidative stress were detected in the salvianolic acid B group. Cystine cytotoxicity in vitro and cystine stone formation in vivo were associated with oxidative stress, and salvianolic acid B could protect against cystine stone-induced injury.

Metabolic evaluation of children with urolithiasis

Aim:

The aim of the study is to identify the prevalence of metabolic abnormalities in children with urolithiasis.

Materials and Methods:

This is a prospective study; all children below 15 years who are found to have urolithiasis were prospectively evaluated with relevant history, clinical examination, and urine and serum testing. Metabolic workup includes complete urine examination, urine culture and sensitivity, and 24-h urinary analysis (lithorisk profile).

Results:

A total of 55 patients are included in the study. Forty-two are boys and 13 are girls aged between from 8 months to 15 years. Thirty-three patients underwent stone analysis, primary composition of calcium oxalate stones in 19 (58%), ammonium urate in 4, dahlite in 3 and uric acid in 3, silicon oxide in 2, and struvite in 2 cases. Lithorisk profile was performed in 40 cases (72.7%). The pH range is 5.6–6.2. We noted hypercalciuria in 20 patients (50%), hyperuricosuria in 23 (57.5%), hyperoxaluria in 20 (50%), hypernatriuria in 26 (65%), hypocitraturia in 9 (23%), and hypomagnesuria in 3 (7.5%). Urine calcium-to-creatinine ratio >0.2 was found in 22 (55%) patients. Statistically significant association between hyperoxaluria and hyperuricosuria (P < 0.04, r = 0.32) and hypercalciuria and hyperuricosuria (P < 0.001, r = 0.51) found in this study. Hyperuricosuria is seen in 75% and 73% of patients with hypercalciuria and hyperoxaluria, respectively. Twenty-five children have both lithorisk profile and stone analysis. Hypercalciuria and hyperoxaluria were noted in 60% of calcium oxalate stone formers each. Elevated urinary calcium/creatinine ratio (>0.2) was seen in 73% of calcium oxalate stone formers.

Conclusion:

Because of high prevalence of metabolic risk factors and the significant risk of lifelong recurrence, all children with urolithiasis need complete evaluation with metabolic workup.

Composition of urinary calculi in infants: a report from an endemic country

Pediatric urolithiasis remains endemic in low-resource countries where infants constitute 17-40% of all children with urolithiasis. This study reports socio-economic factors, medical history and chemical composition of urinary stones in 976 infants of up to 2 years of age. Between 1992 and 2016, 976 infants presented to our institute with 1038 stones. Chemical composition of stones was analyzed by Fourier transformation infrared spectroscopy (FTIR). The mean age of infants was 19.5 ± 5.74 months with a M:F ratio of 5.5:1. Half (50%) of the infants were rural dwellers, 90% belonged to low socio-economic class and 70% were malnourished. A history of chronic diarrhoea was reported in 13% and urinary tract infections in 5%. The anatomic location was bladder in 487 (46.9%), kidney in 246 (23.6%), ureter in 142 (13.6%), urethra in 2 (0.2%) and 161 (15.5%) were passed spontaneously. Overall frequency of compounds in stones showed ammonium acid urate (AAU) in 772 (74.37%), calcium oxalate (CaOx) in 410 (39.5%). Uric acid (UA) in 119 (11.46%), calcium phosphate apatite (CaP) in 96 (9.25%), magnesium ammonium phosphate (Struvite) in 45 (4.34%), cystine in 12 (1.16%) and xanthine in 40 (3.85%). Frequency of compounds was similar in genders. Infants of age 0-6 months had higher frequency of UA (28%), CaOx (50%) and low AAU (61%) as compared to 11, 39 and 75%, respectively, in 7-24 months (p < 0.049) (p < 0.002) (p < 0.001). Nucleus of stones showed pure AAU in 63 and 43% on the surface due to addition of CaOx, struvite and CaP. Our study has shown that AAU is a major component of stones in infants where the main risk factors are poverty, malnutrition, diarrheal diseases and dehydration.

Metabolic disturbances in Chinese children with urolithiasis: a single center report

Urinary stones and urine composition are the first steps in the process of recurrence prevention, but data concerning the association between the two compositions are scarce in Chinese children with urolithiasis. We retrospectively analyzed the records of children (age range 0-18 years) with urolithiasis in our center between March 2004 and December 2013. Stone analysis was carried out in 382 children and 24-hour urine analysis in 80 children. Analysis of both stone and 24-hour urine composition was completed in 56 children. Stone samples were analyzed by Fourier transform-infrared spectrometry. The major stone constituents were calcium oxalate (78.8 %). Of 80 children with 24 h urine analysis, only 2.5 % were without urinary metabolic abnormalities. Hypocitraturia was recorded in 97.5 %, high sodium excretion in 50.0 %, cystinuria in 48.7 %, hypercalciuria in 18.8 %, small urine volumes in 12.5 %, hyperoxaluria in 5.0 % and hyperuricosuria in 1.3 %. Interestingly, higher urine volumes were recorded in girls than in boys (73.2 ± 58.5 vs 51.3 ± 45.3 mL/kg, p = 0.036). Urine sodium (p = 0.002) and oxalate (p = 0.004) were significantly higher in children >9 year old. Moreover, compared with calcium oxalate stone formers, the urine volume (p = 0.040), citrate (p = 0.007) and cystine (p = 0.004) were higher in patients with cystine stones. Hypocitraturia was the common abnormality among Chinese children with urolithiasis. The surprisingly high incidence of cystinuria is of note.

Structural characterization and vibrational studies of human urinary stones from Istanbul, Turkey

Seven human urinary stones were collected from urinary bladders of patients hailing from Istanbul, Turkey. Their XRD, EDX, FT-IR and FT-Raman spectra as well as SEM images have been recorded to determine their chemical compositions, morphologies, crystal structures, and crystallite sizes. XRD and vibrational (FT-IR and FT-Raman) analyses indicate that six out of the seven stones have identical contents. The ratios of organic and inorganic contents of the stones have been determined by their thermogravimetric analyses. The stones have been found to contain calcium oxalate monohydrate and apatite as the major components.

How should patients with cystine stone disease be evaluated and treated in the twenty-first century?

Cystinuria continues to be one of the most challenging stone diseases. During the latest decades our knowledge of the molecular basis of cystinuria has expanded. Today 160 different mutations in the SLC3A1 gene and 116 in the SLC7A9 gene are listed. The full implications of type A, B or AB status are not yet fully understood but may have implications for prognosis, management and treatment. Despite better understanding of the molecular basis of cystinuria the principles of recurrence prevention have remained essentially the same through decades. No curative treatment of cystinuria exists, and patients will have a life long risk of stone formation, repeated surgery, impaired renal function and quality of life. Therapy to reduce stone formation is directed towards lowering urine cystine concentration and increasing cystine solubility. Different molecules that could play a role in promoting nucleation and have a modulating effect on cystine solubility may represent new targets for cystinuria research. Investigation of newer thiol-containing drugs with fewer adverse effects is also warranted. Determining cystine capacity may be an effective tool to monitor the individual patient's response. Compliance in cystinuric patients concerning both dietary and pharmacological intervention is poor. Frequent clinical follow-up visits in dedicated centres seem to improve compliance. Cystinuric patients should be managed in dedicated centres offering the complete range of minimal invasive treatment modalities, enabling a personalized treatment approach in order to reduce risk and morbidity of multiple procedures.

A Comparison between Clinical and Metabolic Features of Renal Calyceal Microlithiasis and Overt Urolithiasis in Different Pediatric Age Groups

INTRODUCTION

This study assesses the differences in the presentations, complications and metabolic abnormalities of children with renal calyceal microlithiasis (RCM) and overt urolithiasis in different pediatric ages.

MATERIALS AND METHODS

A total of 465 children with urolithiasis were investigated retrospectively. Patients were categorized based on their ages to infancy, early childhood, middle childhood and adolescence. When the hyperechogenic spots on ultrasound imaging were <3 mm, they were considered RCM, and if they were ≥3 mm, they were considered overt urolithiasis.

RESULTS

Metabolic abnormalities were detected in 71%; hyperuricosuria in infants, hyperoxaluria in younger children and hypocitraturia in older children were the most common metabolic abnormalities. Hypercalciuria was the only metabolic abnormality that was significantly associated with overt urolithiasis in all pediatric ages (OR 2.25, 95% CI 1.21-4.19). The clinical presentations were not significantly different between RCM and overt urolithiasis; however, complications such as urinary tract infection was significantly higher with overt urolithiasis in infancy (p = 0.01), early childhood (p = 0.02), middle childhood (p = 0.007) and adolescence (p = 0.01). Also, growth retardation was significantly higher with overt urolithiasis in infancy and early childhood (p = 0.02).

CONCLUSIONS

Most children with urolithiasis have underlying urinary metabolic abnormalities that differ according to the child's age. Despite these differences, hypercalciuria is significantly associated with overt urolithiasis in all pediatric ages. Clinical and laboratory features cannot differentiate RCM and overt urolithiasis; however, complications are significantly higher with overt urolithiasis.