title: Factors increasing the risk for stone formation in adult patients with cystic fibrosis.
abstract: 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.
authors.affiliation: Department of Nephrology and Renal Stone Centre, Pellgrini Hospital Napoli, Italy. maurizio.terribile@fastwebnet.it
authors.forename: Maurizio
authors.initials: M
authors.lastname: Terribile
authors.forename: Maria
authors.initials: M
authors.lastname: Capuano
authors.forename: Giovanni
authors.initials: G
authors.lastname: Cangiano
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Carnovale
authors.forename: Pietro
authors.initials: P
authors.lastname: Ferrara
authors.forename: Michele
authors.initials: M
authors.lastname: Petrarulo
authors.forename: Martino
authors.initials: M
authors.lastname: Marangella
mesh_terms: D000328:Adult; D002129:Calcium Oxalate / Q000652:urine; D003404:Creatinine / Q000652:urine; D003550:Cystic Fibrosis / Q000150:complications*; D005260:Female; D006579:Heterozygote; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007669:Kidney Calculi / Q000150:complications* / Q000209:etiology*; D008297:Male; D008875:Middle Aged; D053040:Nephrolithiasis / Q000150:complications* / Q000209:etiology; D015995:Prevalence; D012307:Risk Factors; D014527:Uric Acid / Q000652:urine
chemical_list: D002129:Calcium Oxalate; D014527:Uric Acid; D003404:Creatinine