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Oxalate and calcium excretion in cystic fibrosis
M A Turner1, D Goldwater, T J David
1University Department of Child Health, Booth Hall Children's Hospital, Charlestown Road, Blackley, Manchester M9 7AA, UK. mark.turner@man.ac.uk
Insights
Children with cystic fibrosis (CF) often have high oxalate excretion, a risk factor for kidney stones. However, low calcium excretion may offer protection against stone formation in these patients.
Area of Science:
- Pediatric Nephrology
- Cystic Fibrosis Research
- Urolithiasis
Background:
- Cystic Fibrosis (CF) is associated with an increased risk of renal complications, including calcium oxalate stones.
- A case of recurrent calcium oxalate nephrolithiasis in a child with CF prompted this investigation.
Purpose of the Study:
- To identify risk factors for renal stone formation in children with Cystic Fibrosis.
- To assess urinary excretion of calcium, oxalate, and glycolate in children with CF.
Main Methods:
- Twenty-four-hour urinary excretion of calcium, oxalate, and glycolate was measured in 26 children with CF (aged 5-15.9 years).
- Participants maintained their normal diet and treatments during the study period.
Main Results:
- Elevated urinary oxalate excretion was observed in 14 out of 26 children, with excretion correlating positively with age.
- A positive correlation was found between urinary oxalate and glycolate excretion.
- Mean urinary calcium excretion was low (0.06 mmol/kg/24 h), with 21 out of 24 children exhibiting hypocalciuria.
Conclusions:
- Hyperoxaluria in children with CF may be linked to malabsorption and metabolic processes.
- The observed hypocalciuria might be a protective factor against the development of renal stones in this population.
Background:
A patient with cystic fibrosis (CF) and repeated calcium oxalate renal stones prompted us to investigate other children for risk factors for this recognised complication of CF.
Methods:
Twenty four hour urinary excretion of calcium, oxalate, and glycolate was measured in children with CF and no symptoms of renal tract stones. Normal diet and treatments were continued.
Results:
In 26 children (aged 5-15.9 years) oxalate excretion was correlated with age; 14 of 26 children had oxalate excretion above an age appropriate normal range. There was a positive correlation between oxalate excretion and glycolate excretion. Mean calcium excretion was 0.06 mmol/kg/24 h with 21 of 24 children having calcium excretion below the normal range.
Conclusions:
Hyperoxaluria may reflect malabsorption although correlation between excretion of oxalate and glycolate suggests a portion of the excess oxalate is derived from metabolic processes. The hypocalciuria observed here may protect children with CF from renal stones.