Which factors account for renal stone formation in cystic fibrosis?

Aims: Studies dealing with the increased tendency to stone formation noted in cystic fibrosis, focus on enteric hyperoxaluria. It is well recognized, however, that low urine volume, hypocitraturia and perhaps even hypercalciuria are further risk factors for stone formation. Methods: Nineteen patients with cystic fibrosis (14 boys and 5 girls, aged 10 - 23, median 15 years) underwent a standard protocol for metabolic evaluation of the lithogenic tendency. In 10 patients, the study was repeated after treatment with recombinant human growth hormone 43 g/kg body weight daily for 12 months. Results: The metabolic evaluation disclosed low urine output in 12, hyperoxaluria in 8 and hypocitraturia in 9 of the 19 cystic fibrosis patients. The mentioned parameters were not influenced by treatment with recombinant human growth hormone. Conclusion: The report indicates that in cystic fibrosis low urine volume, hypocitraturia and hyperoxaluria act in concert and contribute to the likelihood of stone formation. This tendency is not modified by treatment with recombinant human growth hormone.