NDT Advance Access originally published online on April 4, 2006
Nephrology Dialysis Transplantation 2006 21(7):1870-1875; doi:10.1093/ndt/gfl067
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© The Author [2006]. Published by Oxford University Press on behalf of ERA-EDTA. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org
Original Articles: Clinical Nephrology
Factors increasing the risk for stone formation in adult patients with cystic fibrosis
Department of Nephrology and Renal Stone Centre, Pellegrini Hospital, Napoli, 1 Cystic Fibrosis Centre, Campania Regional Adult Unit, University Federico II, Naples and 2 Department of Nephrology and Renal Stone Centre, Mauriziano Hospital, Torino, Italy
Correspondence and offprint requests to: Dr Maurizio Terribile, MD, Centro Calcolosi Renale, Dipartimento di Nefrologia, Ospedale dei Pellegrini, Via Portamedina 41, 80134 Napoli, Italia. Email: maurizio.terribile{at}fastwebnet.it
Background. Patients with cystic fibrosis (CF) are at high risk of nephrolithiasis (NL), but controversy still exists in terms of causes, including low urine output, hypercalciuria, hyperoxaluria, hyperuricosuria and hypocitraturia. Moreover, heterozygotes (H-CF), which may exhibit altered renal concentrating and diluting ability, have never studied so far. We, therefore, evaluated the metabolic and physicochemical data of adult CF and H-CF patients, comparing them to controls (C).
Methods. Twenty-nine CF patients (16 females, aged 28.4±7.1 years), 20 H-CF (12 females, aged 58.6±6.3 years) and 30 C (19 females, aged 39.1±11.5 years) underwent kidney ultrasound and metabolic evaluation to assess stone risk profile.
Results. There was a 21% prevalence of NL in CF vs 15% in H-CF. The CF group had elevated uric acid, but no other serological differences compared with the H-CF and C group. Conversely, the citrate and oxalate content in the urine differed significantly, being lower and higher, respectively. These changes held after correction for urine creatinine. Consequently, urine specimens were more supersaturated with calcium oxalate, despite exhibiting no differences for other relevant constituents. Uric acid increased only after normalization for the body weight and urine creatinine. Lower urine volume and more acidic pH produced mild supersaturation with uric acid in samples from CF, while urine from both H-CF and C remained undersaturated. H-CF had only minor increases in both urine oxalate and calcium oxalate supersaturation.
Conclusions. This study confirms a high prevalence of kidney stones among CF patients associated with supersaturated urine. Their longer survival justifies diets and/or medications aimed at reducing the risk of forming stones.
Keywords: calcium oxalate; cystic fibrosis; hyperoxaluria; hyperuricosuria; hypocitraturia; nephrolithiasis