Risk of urolithiasis in patients with cystic fibrosis

INTRODUCTION: It has been generally admitted that kidneys are not affected in Cystic fibrosis (CF) patients. Anyway, there are several studies demonstrating a higher prevalence of calcium oxalate nephrolithiasis prevalence in CF patients compared to normal population. The aim of our study was to evaluate renal disease regional prevalence in CF patients METHODS: Cross-sectional regional controlled study. Index group = 20 CF subjects 4- 30 years old controlled in a CF outpatient clinic in a tertiary hospital. Control group = 73 healthy subjects randomly selected among the 100 subjects who completed the follow-up visits of the RICARDIN study. Physical examination and renal function analysis were conducted in both groups. CF patients had their functional measurements repeated in a 20 month interval. Renal ultrasonography was performed only in CF patients. RESULTS: Height estimated creatinine clearance in CF patients were not statistically different from controls. Oxaluria (0.77 mg/kg/24 h, p = 0.001) and phosphate excretion (18.98 mg/kg/24 h, p = 0.04) were significantly higher while citrate (7.76 mg/kg/24 h, p = 0.04) and magnesium (1.60 mg/kg/24 h, p = 0.04) excretion were significantly lower in CF patients than normal population reference values. No signs of nephrolithiasis or nephrocalcinosis were found. CONCLUSIONS: CF patients showed a conserved renal function , without ecographic abnormalities. CF patients showed increased urinary elimination of phosphate and oxalate and lower citrate and magnesium elimination, findings that predispose these patients to suffer from urolithiasis in the future.