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

Age-Specific Excretion of Calcium, Oxalate, Citrate, and Glycosaminoglycans and Their Ratios in Healthy Children and Children with Urolithiasis

We analyzed children with urolithiasis with age- and gender-matched healthy children. Calcium (mmol/mmol creatinine) and the calcium/citrate ratio (mol/mmol) are the only variables that differentiate children before puberty from healthy children (ROC analysis confirmed only calcium/citrate as a significant variable with cut-off value > 0.84). Peri-pubertal children are distinguished from age- and gender-matched healthy children by the following variables: citrate (mmol/mol creatinine), calcium/citrate (mol/mmol), oxalate/glycosaminoglycans (mmol/g), oxalate/citrate ratios (mmol/mmol) and oxalate/(citrate × glycosaminoglycans) (mol oxalate × mol creatinine)/(mol citrate × g glycosaminoglycans). All variables were confirmed by ROC analysis with cut-off values ≤ 327.87, >1.02, >11.24, >0.12 and >0.03, respectively. These results indicate a different risk of urinary stones development before puberty vs. pubertal/postpubertal children and increasing importance (deficiency) of citrate and glycosaminoglycans in such children. J48 classifier confirmed the importance of the oxalate/(citrate × glycosaminoglycans) and the calcium/citrate ratios (Ox/Cit × GAG 0.22 and Cit/GAG 0.612) with the practically applicable classification tree for distinguishing between pubertal/postpubertal children with urolithiasis with age- and gender-matched healthy children.

Calcium oxalate urolithiasis in children: urinary promoters/inhibitors and role of their ratios

Diagnostic criteria for determination of inclination towards idiopathic calcium oxalate (CaOx) urolithiasis based on biochemical urine parameters are not sufficiently well defined in children. The aim of this study was to determine the risk of CaOx urolithiasis in children from concentrations of calcium, oxalate, citrate, and glycosaminoglycans in urine and their ratios, all standardized in respect to creatinine. We collected and analyzed 24-h urine samples of children with CaOx urolithiasis (n = 61) and compared with urine samples of matched control group of healthy children (n = 25). The study has showed that all stone formers have higher excretion of calcium (mmol/mmol creatinine), calcium/citrate (mol/mmol), and oxalate/(citrate × glycosaminoglycans) ratio (mol Ox × mol cr)/(mol Cit × g GAGs). ROC analysis of these variables gave criteria (>0.28, >1.07, and >0.08, respectively) for distinguishing stone formers from healthy children. Biochemical urine parameters and their ratios (calcium, calcium citrate, and oxalate/(citrate × glycosaminoglycans) enable one to discriminate idiopathic calcium oxalate stone formers from healthy children. Oxalate/(citrate × glycosaminoglycans) ratio per se can serve as an independent risk for stone formation.

CONCLUSION

Using biochemical urine parameters and their ratios such as calcium, calcium/citrate, and oxalate/(citrate × glycosaminoglycans) enables one to determine diagnostic criteria towards idiopathic calcium oxalate urolithiasis in children. What is known: • The role of urine calcium as a promoter in calcium oxalate urolithiasis is well established. • Seldom used calcium/citrate ratio is acknowledged as a risk factor for calcium/oxalate urolithiasis. What is new: • The values of calcium and citrate in clinically and genetically proven idiopathic calcium oxalate urolithiasis make calcium/citrate ratio useful for diagnostic purposes in such stone formers. • Rarely used calcium independent oxalate/(citrate x glycosaminoglycans) ratio serves as the second best high specificity marker for idiopathic calcium oxalate urolithiasis.

Demographic characteristics and metabolic risk factors in Croatian children with urolithiasis

The aim of this study was to assess demographic data, clinical presentation, metabolic features, and treatment in 76 children with urolithiasis presented from 2002 to 2011. Urolithiasis is responsible for 2.5/1,000 pediatric hospitalizations, with new cases diagnosed in 1.1/1,000 admissions. From the observed period, two-fold rise of incidence rate was observed. Compiling the data from other pediatric institutions in our country, we estimated present overall incidence rate in Croatia as 6.5/100,000 children under 18 years. There were 41 boys and 35 girls (ratio 1.17:1). The mean age at diagnosis was 9.7 (range 0.8-16) years and follow-up duration was 5.3 (range 1.8-10) years. Renal colic (75.0 %) and hematuria (57.89 %) were the main symptoms. In 65.78 % of children, stones were unilateral. Stones were located in kidney in 52.63 %, in the ureter in 26.32 %, and in bladder in 6.58 % cases. Stone analysis showed calcium oxalate in 75.0 % of the cases. Associated urinary tract abnormalities were found in 19.73 % children. Most common metabolic disturbances were hypercalciuria (47.37 %) and idiopathic or mild hyperoxaluria (18.42 %). Urine saturation (EQUIL2) was elevated in 61.84 % cases. Spontaneous stone evacuation occurred in 51.21 % children. Extracorporeal shock wave lithotripsy, surgical evacuation, and endoscopic removal of calculi were performed in 21.0, 6.58, and 5.26 % of cases, respectively. Follow-up conservative therapy, consisting of fluid/diet recommendations and additional potassium citrate and/or chlorothiazide in children with increased risk, was sufficient for stone recurrence prevention in 92.1 % of children. In conclusion, the study gave insight in epidemiology and metabolic disturbances of urinary stone disease in Croatian children.

Overweight and obesity: risk factors in calcium oxalate stone disease?

Introduction. Several studies showed an association of overweight and obesity with calcium oxalate stone disease (CaOx). However, there are no sufficient data on the influence of body weight on the course of the disease and the recurrence rate. Patients and Methods. N = 100 consecutive stone formers with pure CaOx were studied. Different parameters were investigated. According to the BMI, patients were divided into three groups: (1) BMI ≤ 25; (2) BMI 25.1-30; (3) BMI > 30. Results. N = 32 patients showed a BMI ≤ 25, n = 42 patients showed a BMI of 25.1-30 and n = 26 patients showed a BMI ≥ 30. The groups differed significantly concerning BMI (by definition), urine pH, and urine citrate. The recurrence rate was not significantly different. Discussion. Our study demonstrated that body weight negatively influences single risk factors in CaOx, but obesity is not a predictor for the risk of recurrence in CaOx.

Biochemical risk factors for stone formation in a Scottish paediatric hospital population

Background

Renal stones in children, although rare, may be associated with morbidity and renal damage. Scottish children have a different ethnic composition and diet compared with paediatric populations previously studied. Urinary stone promoters include calcium, oxalate and urate. Postulated inhibitors include citrate and glycosaminoglycans (GAGs). We tested the hypothesis that Scottish paediatric stone-formers have higher excretion of urinary stone promoters (calcium/oxalate/urate) and/or lower excretion of stone inhibitors (citrate/GAGs) than children with isolated haematuria and controls.

Methods

In this case-controlled study, we measured creatinine, calcium, oxalate, urate, citrate and GAGs in random urine samples from 24 stone-formers (excluding inherited metabolic disorders), median age 10.2 (range 1.0–17.2) y; 25 patients with isolated haematuria, 6.3 (0.6–13.7) y; and 32 controls, 7.5 (0.8–14.7) y.

Results

Excretion of urinary promoters and inhibitors differed among stone-formers, haematuria and control groups for (median (range)): calcium (0.82 (0.02–2.19), 0.43 (0.08–2.65), 0.31 (0.04–2.12) mmol/mmol creatinine, respectively, P = 0.005), citrate (0.42 (0.13–0.72), 0.33 (0.05–0.84), 0.61 (0.11–1.75) mmol/mmol creatinine, P = 0.001), calcium:citrate ratio (1.68 (0.19–4.81), 1.30 (0.19–9.57), 0.54 (0.10–2.27) mmol/mmol, P < 0.0001) and the promoter:inhibitor ratio (calcium × oxalate)/(citrate × GAGs) (8.3 (1.0–82.5), 4.3 (1.2–69.5), 2.8 (0.3–13.2) mmol/g, P < 0.0001).

Conclusions

Scottish paediatric stone-formers had lower urinary citrate excretion and higher urinary calcium excretion, calcium:citrate ratio and promoter:inhibitor ratio compared with controls. Urinary calcium excretion and promoter:inhibitor ratio was also higher than children with isolated haematuria. Nevertheless, marked overlap between the stone-former and haematuria groups for promoter:inhibitor and calcium:citrate ratios suggests that some patients with isolated haematuria may be at future risk of urolithiasis.