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Biochemical risk factors for stone formation in a Scottish paediatric hospital population
Lyndsey MacDougall1, Sepideh Taheri, Patricia Crofton
1Department of Paediatric Biochemistry, Royal Hospital for Sick Children, Edinburgh, Scotland, UK. lyndsey.macdougall@luht.scot.nhs.uk
Insights
Scottish children who form kidney stones have lower citrate and higher calcium in their urine compared to controls. This imbalance may indicate a future risk for urolithiasis in some children with isolated haematuria.
Area of Science:
- Pediatric Nephrology
- Urology
- Biochemistry
Background:
- Renal stones in children can lead to significant morbidity and renal damage.
- Scottish children present unique demographic and dietary factors influencing stone formation.
- Urinary stone promoters (calcium, oxalate, urate) and inhibitors (citrate, glycosaminoglycans) are key factors in pediatric urolithiasis.
Purpose of the Study:
- To investigate urinary stone promoter and inhibitor levels in Scottish children.
- To test the hypothesis of altered urinary profiles in pediatric stone-formers compared to controls and those with isolated hematuria.
Main Methods:
- A case-controlled study involving 24 stone-formers, 25 children with isolated hematuria, and 32 controls.
- Measurement of urinary creatinine, calcium, oxalate, urate, citrate, and glycosaminoglycans (GAGs) in random urine samples.
- Analysis of promoter:inhibitor ratios and calcium:citrate ratios.
Main Results:
- Stone-formers exhibited significantly higher urinary calcium and lower citrate excretion than controls.
- The calcium:citrate ratio and the promoter:inhibitor ratio were significantly higher in stone-formers compared to both controls and children with isolated hematuria.
- Elevated promoter:inhibitor and calcium:citrate ratios were observed in some children with isolated hematuria, suggesting potential future risk.
Conclusions:
- Scottish pediatric stone-formers show distinct urinary profiles with lower citrate and higher calcium.
- The findings suggest that certain children with isolated hematuria may be at increased risk for developing kidney stones.
- Urinary metabolic profiling is crucial for identifying at-risk pediatric populations for urolithiasis.
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 x oxalate)/(citrate x 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.
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