Aetiology of nephrolithiasis in north Indian children

Metabolic and Genetic Evaluation in Children with Nephrolithiasis

OBJECTIVE

To evaluate metabolic and genetic abnormalities in children with nephrolithiasis attending a referral center in North India.

METHODS

The patients aged 1-18 y old with nephrolithiasis underwent biochemical evaluation and whole-exome sequencing. The authors evaluated for monogenic variants in 56 genes and compared allele frequency of 39 reported polymorphisms between patients and 1739 controls from the GenomeAsia 100 K database.

RESULTS

Fifty-four patients, aged 9.1 ± 3.7 y were included. Stones were bilateral in 42.6%, familial in 33.3%, and recurrent in 25.9%. The most common metabolic abnormalities were hypercalciuria (35.2%), hyperoxaluria (24.1%), or both (11.1%), while xanthinuria (n = 3), cystinuria (n = 1), and hyperuricosuria (n = 1) were rare. Exome sequencing identified an etiology in 6 (11.1%) patients with pathogenic/likely pathogenic causative variants. Three variants in MOCOS and one in ATP7B were pathogenic; likely pathogenic variants included MOCOS (n = 2), AGXT, and SLC7A9 (n = 1, each). Causality was not attributed to two SLC34A1 likely pathogenic variants, due to lack of matching phenotype and dominant family history. Compared to controls, allele frequency of the polymorphism TRPV5 rs4252402 was significantly higher in familial stone disease (allele frequency 0.47 versus 0.53; OR 3.2, p = 0.0001).

CONCLUSION

The chief metabolic abnormalities were hypercalciuria and hyperoxaluria. A monogenic etiology was identified in 11% with pathogenic or likely pathogenic variants using a gene panel for nephrolithiasis. Heterozygous missense variants in the sodium-phosphate cotransporter SLC34A1 were common and required evaluation for attributing pathogenicity. Rare polymorphisms in TRPV5 might increase the risk of familial stones. These findings suggest that a combination of metabolic and genetic evaluation is useful for determining the etiology of nephrolithiasis.

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.

Clinical importance of renal calyceal microlithiasis in children

BACKGROUND

Renal calyceal microlithiasis refers to a hyperechogenic spot in renal calyces <3 mm in diameter detected on renal sonography. These spots possibly represent the first step in calculus formation. The aim of this study was to analyze the clinical presentation, predisposing factors, prognosis and clinical importance of these hyperechogenic spots in renal calyces, renal calyceal microlithiasis, during childhood.

METHODS

The data of 292 children (135 girls, 157 boys) with microlithiasis diagnosed between January 1998 and December 2010 were evaluated retrospectively. Demographic data, serum biochemistry, urinary metabolic factors, and renal sonography results were obtained from patient files. A total of 228 patients were re-evaluated at least 6 months after the first observation of renal calyceal microlithiasis and at 6-12 month intervals thereafter.

RESULTS

Mean age was 16.8 ± 14.9 months, and mean follow-up duration was 14.6 ± 5.9 months. Presenting symptoms were abdominal or flank pain (41.1%), hematuria (35.6%), dysuria (24.7%) and urinary tract infection (34.6%). Previous ultrasounds were normal in 35% of the children. Metabolic and anatomic abnormalities were found in 55.5% and 17.8%, respectively. Hypercalciuria was the most common metabolic abnormality (88.9%). Among 228 patients who had been re-evaluated, microlithiasis disappeared in 37.7%; decreased in number or size in 23.7%; progressed to renal stone formation in 10.6%; increased in number of microlithiasis in 19.0%; and remained unchanged on radiology in 9.0%.

CONCLUSION

Renal calyceal microlithiasis represents a spectrum of clinical situations and underlying metabolic abnormalities that need further investigation in children.

Results of medical treatment and metabolic risk factors in children with urolithiasis

Data on conservative treatment in children with urolithiasis are limited. The aim of the study was to determine the metabolic etiology and results of conservative treatment in children with urolithiasis. We evaluated the clinical presentation and metabolic features of 112 children with urolithiasis. The mean age at diagnosis of urolithiasis was 3.9 (range 0.1-18) years, and follow-up duration was 16.7 (range 1-36) months. The most common presenting symptoms were flank or abdominal pain and restlessness (25%). Urine analysis revealed metabolic abnormalities in 92% of cases, including hypocitraturia (42%), hyperoxaluria (32.1%), hypercalcuria (25%), hyperuricosuria (9.8%), and cystinuria (2.7%). Patients who had metabolic risk factors were treated according to underlying metabolic abnormalities. About half of these patients were stone free or stones were diminished in size. These results showed that early recognition and treatment of urinary metabolic abnormalities will reduce the number of invasive procedures and renal damage in children with urolithiasis.

History, epidemiology and regional diversities of urolithiasis

Archeological findings give profound evidence that humans have suffered from kidney and bladder stones for centuries. Bladder stones were more prevalent during older ages, but kidney stones became more prevalent during the past 100 years, at least in the more developed countries. Also, treatment options and conservative measures, as well as 'surgical' interventions have also been known for a long time. Our current preventive measures are definitively comparable to those of our predecessors. Stone removal, first lithotomy for bladder stones, followed by transurethral methods, was definitively painful and had severe side effects. Then, as now, the incidence of urolithiasis in a given population was dependent on the geographic area, racial distribution, socio-economic status and dietary habits. Changes in the latter factors during the past decades have affected the incidence and also the site and chemical composition of calculi, with calcium oxalate stones being now the most prevalent. Major differences in frequency of other constituents, particularly uric acid and struvite, reflect eating habits and infection risk factors specific to certain populations. Extensive epidemiological observations have emphasized the importance of nutritional factors in the pathogenesis of urolithiasis, and specific dietary advice is, nowadays, often the most appropriate for prevention and treatment of urolithiasis.

Clinical and metabolic features of urolithiasis and microlithiasis in children

We evaluated the clinical, radiological and metabolic features of 162 children with urolithiasis or microlithiasis who had been referred to our pediatric nephrology clinics between 1998 and 2008 with suspected urolithiasis. The medical histories of these children (78 girls, 84 boys), who ranged in age from 2 months to 16 years (mean age 5.59 +/- 0.35 years), were reviewed retrospectively for clinical and metabolic features of urinary tract calculi. Urinary tract infections (UTI) were present in 45.9% of the cases. The most common presenting symptoms were flank pain or restlessness (25.3%) and hematuria (21.6%), followed by UTI (16%), whereas 23.5% of the cases were detected incidentally during evaluation for other medical conditions. Other symptoms at presentation included dysuria, passing stones, penile edema, enuresis, vomiting and anorexia. Urine analysis revealed metabolic abnormalities in 87% of the cases, including hypercalciuria (33.8%), hypocitraturia (33.1%), hyperoxaluria (26.5%), hyperuricosuria (25.4%), hypocitraturia + hypercalciuria (21.1%), hyperphosphaturia (20.8%) and cystinuria (5.7%). Almost 50% of the patients had a positive family history for urolithiasis. The most frequently involved site was in the kidneys (86%). Ureters and bladder were involved in 12 and 2% of the cases, respectively. A family history of urolithiasis, presenting symptoms and underlying metabolic abnormalities were similar for microlithiasis and the patients with larger stones. However, in our study population, microlithiasis was mainly a disease of young infants, with a greater chance for remission and often not associated with structural changes. The presenting symptoms of urolithiasis show a wide spectrum, so that a high index of suspicion is important for early detection. A metabolic abnormality can be identified in 87% of cases of urolithiasis. Detection of microlithiasis may explain a number of symptoms, thus reducing invasive diagnostic procedures and allowing early recognition of metabolic abnormalities. These results draw attention to the importance of screening for UTIs in patients with urolithiasis.

The metabolic etiology of urolithiasis in Turkish children

Pediatric urolithiasis is an endemic disease, especially in certain developing regions of the world, such as the Far East, and to a certain extent the Middle East and Turkey. The aim of the study is to determine the metabolic etiology and the prevalence of formation of urinary calculi in Turkish pediatric patients with urolithiasis. Seventy-two pediatric patients diagnosed as having urolithiasis were studied from 1999-2005 in Dr. Behcet Uz Child Disease and Surgery Education and Research Hospital Nephrology Department, Izmir, according to their presenting signs and clinical and laboratory findings. The other necessary tests were also applied to detect the etiology of the calculi formation. Of the 72 patients, 50 (69.4%) were male and 22 (30.6%) were female, with ages ranging from 2 to 168 months (mean age 72 +/- 35.7 months), and the male-to-female ratio of patients was 2.3. Twenty-four (33%) of them were diagnosed as having metabolic urolithiasis, 21 (30%) anatomic, 19 (26%) infectious and 8 (11%) idiopathic. The age at which urolithiasis was first diagnosed was found to be low in the metabolic and anatomic etiology groups (P = 0.028). Thirteen patients (18%) with urolithiasis were known to have a family history of stone disease, and in all of them metabolic etiology was considered to be the reason (P < 0.001). In all of the groups, the localization of the stone was found to be the upper urinary system most of the time, and in 17 (24%) with bilateral multiple stones, the etiology was found to be metabolic (P < 0.001). All of the patients were followed up for 3-72 months (mean 29.2 +/- 13.7 months), and four of them (5.5%) had recurrences. In order to prevent renal damage and recurrences in pediatric patients with urolithiasis in Turkey in whom the etiology is mostly metabolic, the illnesses must be investigated very cautiously, and their early diagnosis and treatment modalities must be considered.

Analysis of calcium, oxalate, and citrate interaction in idiopathic calcium urolithiasis in children

The majority of urinary stones in children are composed of calcium oxalate. To investigate the interaction between urinary calcium, oxalate, and citrate as major risk factors for calcium stones formation, their 24-h urinary excretion was determined in 30 children with urolithiasis and 15 normal healthy children. The cutoff points between children with urolithiasis and healthy children, accuracy, sensitivity, and specificity for each risk factor alone as well as for all three taken together were determined. OneR and J4.8 classifiers as parts of the larger data mining software Weka, based on machine learning algorithms, were used for the determination of the cutoff points for differentiation of the children. The decision tree based on J4.8 classifier analysis of all three risk factors together proved to be the best for differentiating stone formers from normal children. In comparison to the accuracy of the differentiation after calcium and oxalate of 80% and 75.6%, respectively, the decision tree showed an accuracy of 97.8%. Even when its stability was tested by the leave-one-out cross-validation procedure, the accuracy remained at a very acceptable percentage of 93.2% correctly classified patients. J4.8 classifier analysis gave a look inside urinary calcium, oxalate, and citrate interaction. Urinary calcium excretion was shown as the most informative in discrimination of the children with urolithiasis from healthy children. However, it was shown that oxalate and citrate excretions might influence the stone formation in a subpopulation of the stone formers. In patients with low urinary calcium, a major role in lithogenesis belongs to oxalate, in some of them alone and in others in conjunction with citrate. Decreased urinary citrate excretion in the presence of increased oxalate excretion may lead to stone formation.

Pediatric urolithiasis: developing nation perspectives

PURPOSE

We evaluated epidemiology, etiology, dietary and urinary risk factors, and the composition of calculi in pediatric stone formers in Pakistan.

MATERIALS AND METHODS

This retrospective study includes 1,440 children treated between 1987 and 2000. Case records were reviewed for demographics, etiology and clinical symptoms. Dietary and urinary risk factors were analyzed prospectively in idiopathic stone formers. Stone composition was analyzed by infrared spectroscopy.

RESULTS

There were 1,075 males and 365 females for a male-to-female ratio of 3:1. The peak age for renal and bladder stones was 6 to 10 and 1 to 5 years, respectively. Overall 795 stones (55%) were renal, 198 (14%) were ureteral and 447 (31%) were vesical. Bladder stones were present in 60% of cases in the mid 1980s but decreased to 15% in the mid 1990s. The clinical symptoms were abdominal pain in 511 patients (51%) and fever in 193 (19.5%). There were anatomical abnormalities in 96 patients (12%), metabolic abnormalities in 206 (25%), infection stones in 60 (7%) and idiopathic stones in 444 (55%). Urinary analysis in idiopathic stone formers revealed hypercalciuria in 17 (11%), hyperoxaluria in 62 (40%), hyperuricosuria in 41 (27%) and hypocitruria in 97 (63%). Diet involved a low intake of protein in 60 cases (44%), calcium in 45 (33%), potassium in 105 (77%) and high oxalate in 75 (55%). The composition was calcium oxalate in 362 stones (47%), ammonium hydrogen urate in 210 (27%) and struvite in 49 (6.4%). Stones recurred in 30 patients (2%).

CONCLUSIONS

The pattern of calculous disease changed from a predominantly lower tract site in the mid 1980s to the upper tract in the mid 1990s. Stone composition, urinary risk factors and dietary analysis suggest that diet, dehydration and poor nutrition are the main causative factors of stone disease.

Characteristics of pediatric urolithiasis in south-east Anatolia

BACKGROUND

Urolithiasis is endemic in Turkey and characteristics of urolithiasis vary in different regions of the world. The aim of the present study was to evaluate the etiological and clinical characteristics and course of pediatric urolithiasis in south-east Turkey.

METHODS

The study population consisted of 81 children (52 girls) with urolithiasis at a mean age of 6.2 +/- 4.2 years who were followed up for 1-32 months.

RESULTS

Metabolic disorders, anatomical defects and infection stones were found to be the etiological factor in 34.6, 29.6 and 22.2% of patients, respectively, while 13.6% of patients were considered idiopathic. Of all patients, 28.4% were admitted with acute renal failure (ARF) and 72.8% had urinary tract infection. Recurrence was seen in 19.8% of patients at presentation. The localization of the stone was found to be in the upper urinary tract, the lower urinary tract or both in 65.4, 14.8% and 17.3% of patients, respectively. Patients with multiple and bilateral stones had a higher risk for ARF than the others. The risk for chronic renal failure was significantly higher in children with multiple, bilateral or recurrent stones and with ARF at presentation.

CONCLUSIONS

Early diagnosis and management of renal stones and urinary tract infections is necessary to prevent the development of ARF or chronic renal failure and to improve the quality of a patient's life.

Urinary oxalate excretion in urolithiasis and nephrocalcinosis

AIMS

To investigate urinary oxalate excretion in children with urolithiasis and/or nephrocalcinosis and to classify hyperoxaluria (HyOx).

METHODS

A total of 106 patients were screened. In those in whom the oxalate: creatinine ratio was increased, 24 hour urinary oxalate excretion was measured. Liver biopsy and/or genomic analysis was performed if primary hyperoxaluria (PH) was suspected. Stool specimens were examined for Oxalobacter formigenes in HyOx not related to PH type 1 or 2 (PH1, PH2) and in controls.

RESULTS

A total of 21 patients screened had HyOx (>0.5 mmol/24 h per 1.73 m(2)); they were classified into five groups. Eleven had PH (PH1 in nine and neither PH1 nor PH2 in two). Six had secondary HyOx: two enteric and four dietary. Four could not be classified. Seven patients had concomitant hypercalciuria. Only one of 12 patients was colonised with O formigenes compared to six of 13 controls.

CONCLUSIONS

HyOx is an important risk factor for urolithiasis and nephrocalcinosis in children, and can coexist with hypercalciuria. A novel type of PH is proposed. Absence of O formigenes may contribute to HyOx not related to PH1.

Urolithiasis: a tribal scenario

Urolithiasis is quite prevalent in Satpura belt of Central India. Forty five children with urolithiasis were studied in Jawahar Medical Foundations Hospital, Dhule, Maharashtra over a period of three years. The mean age was 7.1 +/- 3.2 (range 18 months-15 years). The chief presenting complaints were dysuria and lower abdominal pain. The physical, laboratory and radiographic findings were evaluated. Calculi were located in the bladder (80%), urethra (9%), kidney (6.6%) and ureter (4.4%). Calculi were mainly composed of calcium oxalate (65.7%) and calcium phosphate (34.3%). The predominant urinary tract stones in the tribal Satpura belt are bladder stones and may be related to poor nutrition, low socioeconomic status and consumption of bajra (millet) as staple food as found in this region (93.5%).

Renal stone disease in children

Renal stone disease has been regarded as an uncommon problem in children compared to adults. However, increased awareness of this problem in children may lead to early intervention preventing long-term consequences on the kidney and the urinary tract. This article reviews the epidemiology, pathogenesis, and the most common etiologies of renal stones in children. The clinical features and diagnostic and therapeutic modalities for the specific etiologies are also outlined. Using these guidelines may be helpful not only in the treatment but also in the prevention of renal stones.