Assessment of crystallization risk formulas in pediatric calcium stone-formers

Abstract

The pathogenesis of calcium urolithiasis involves complex interactions of urinary promoters and inhibitors of crystallization. A variety of risk formulas have been established to approximate these interactions for clinical evaluation, and the aim of our study was to determine their usefulness as predictors of stone formation. The study cohort comprised 126 patients (63 boys and 63 girls) aged 6.7-18 years (mean age 14.1 +/- 2.9 years) with calcium urolithiasis (61 with chemically confirmed calcium oxalate stones and 65 children with a strong clinical suspicion of this type of urolithiasis). Of these, 36 children were classified as recurrent stone-formers, whereas the remaining 90 had experienced only one stone episode. The values obtained were compared to those of a control group of 60 age- and gender- matched healthy children. A number of crystallization risk indices were calculated from analytes obtained in 24-h urine: calcium/magnesium ratio (Ca/Mg), calcium/citrate ratio (Ca/Cit), (calcium x oxalate)/(magnesium x citrate) ratio (CaOx/MgCit), relative urinary CaOx supersaturation (RS(CaOx)), CaOx activity product index (AP(CaOx)), and standardized CaOx activity product index (AP(CaOx stand)). All indices, except for the AP(CaOx) index, were significantly higher in stone-formers than in the controls. The Ca/Mg, Ca/Cit, CaOx/MgCit, AP(CaOx), and AP(CaOx stand) indices were significantly higher in recurrent stone-formers than in first-episode ones. However, the determination of precise cutoffs between pathological and non-pathological values was problematic due to a considerable overlap of individual values. Based on our results, we conclude that calculation of the majority of risk indices may play a rather supplementary role in the evaluation of children with calcium urolithiasis.

Enteric hyperoxaluria, recurrent urolithiasis, and systemic oxalosis in patients with Crohn’s disease

“…Interestingly, however, the urinary saturation index for calcium-oxalate was not statistically different in Crohn's patients with and without urolithiasis, but was significantly higher in patients post-bowel resection, compared with those who had not undergone resection (Table 1). However, according to our own experience, calculation of such saturation indexes does not really depict true urinary supersaturation [28]. For example, in patients with the most severe form of hyperoxaluria, primary hyperoxaluria type I, urinary saturation is supposed to be high based on the extreme hyperoxaluria, but on the contrary saturation programs calculate it to be low [29].…”

An Update on the Changing Epidemiology and Metabolic Risk Factors in Pediatric Kidney Stone Disease

“…Children have higher urinary calcium excretion than adults when adjusted for creatinine excretion or body weight (32,36 -38). Studies also show that children have higher urinary SS CaP than adults (32) and that stoneforming children have higher SS CaOx than non-stoneforming children (39,40). In addition, recurrent pediatric SFs have higher calcium excretion when adjusted for creatinine excretion or body weight than solitary pediatric SFs, but this did not translate into significantly different SSs (40,41).…”

“…Urinary citrate levels are highest in young children and decrease into adulthood (32,33), but relative hypocitraturia is a common finding in pediatric nephrolithiasis (22,23,28,39,40,51,52). Hypocitraturia has also been shown to be a risk factor for recurrent stone disease in children (37,41).…”

“…A group from Turkey found that hypomagnesuria was more commonly associated with nephrolithiasis in children than in adults (57). Stone-forming children have a higher urinary calcium-to-magnesium ratio than nonstone-forming children, and children with recurrent stones have a higher calcium-to-magnesium ratio than solitary SFs (40). Treatment with oral magnesium alone has not been shown to improve stone risk, although risk improves when combined with citrate supplementation (58,59).…”

Urinary excretion of calcium, magnesium, phosphate, citrate, oxalate, and uric acid by healthy schoolchildren using a 12-h collection protocol

“…Also, we would like to get information on the normal dietary intake (specific normal values related to formula, or breast-fed infants [8]) and dietary excess (e.g., spinach, rhubarb) in the younger child [9]. As soon as 24-h urine collections are possible, I switch to that procedure, as, in my own experience, very frequently molar creatinine ratios of lithogenic and stone inhibitory factors or other calculated ratios (e.g., Ca/Ci [10]) fluctuate so much that a true diagnostic "red" line cannot be demonstrated.…”