Prevalence of fasting hypercalciuria associated with increased citraturia in the ambulatory evaluation of nephrolithiasis.
BACKGROUND
Nephrolithiasis is a common, high costing pathology of the urinary tract. The most common urinary abnormalities are fasting hypercalciuria, hypercalciuria and hypocitraturia. This study aimed to identify the principal urinary abnormalities in our patients.


METHODS
Ninety-eight patients (pts) (43 females, 55 males) with recurrent calcium nephrolithiasis underwent metabolic evaluation. In two 24-hr urine collections the following parameters were evaluated: calcium, phosphate, sodium, potassium, chloride, magnesium, citrate, oxalate, uric acid, creatinine (Cr), urea, ammonium and pH; blood measurement of calcium, phosphate, sodium, potassium, chloride, magnesium, uric acid, Cr, urea, acid-base balance ionized calcium and intact parathyroid hormone (iPTH) were also performed. A first morning voided urine sample was collected for measuring the urinary cross-links and fasting calciuria. The tubular threshold of phosphate (TmP) was calculated according to Walton and Bijovet. Metabolic evaluation was repeated in 63/98 pts after 7 days on a low calcium diet.


RESULTS
The most common urinary abnormalities were fasting hypercalciuria in 51/96 pts (53.1%), hypercalciuria in 33/97 pts (34%) and hypocitraturia in 29/98 pts (29%); 24/33 pts (73%) with hypercalciuria had fasting hypercalciuria. Hypercalciuria was partially corrected on the calcium-restricted diet, while fasting hypercalciuria was not. Urine citrate levels were significantly higher in patients with fasting hypercalciuria.


CONCLUSIONS
Fasting hypercalciuria was the most frequent urinary abnormality and it was not corrected with a calcium-restricted diet. In fasting hypercalciuric patients, increased bone resorption activity could be responsible for higher citraturia levels.
Damasio
Beatrice
B
Division of Nephrology, San Martino Hospital, Genoa, Italy. beatrice.damasio@libero.it
Massarino
Fabio
F
Durand
Felice
F
Banchero
Riccardo
R
Bottino
Paolo
P
De Franchis
Vincenzina
V
Carmignani
Giorgio
G
Cannella
Giuseppe
G
D002118:Calcium / Q000652:urine*; D002136:Calcium, Dietary / Q000008:administration & dosage; D002951:Citrates / Q000652:urine*; D004305:Dose-Response Relationship, Drug; D005215:Fasting / Q000652:urine; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007669:Kidney Calculi / Q000178:diet therapy / Q000453:epidemiology / Q000652:urine*; D008297:Male; D008875:Middle Aged; D018670:Monitoring, Ambulatory; D010045:Outpatients; D015995:Prevalence; D012008:Recurrence; D012189:Retrospective Studies
D002136:Calcium, Dietary; D002951:Citrates; D002118:Calcium