[Indication of the urinary citrate levels in idiopathic renal calculosis]

The reported incidence of hypocitraturia among stone formers (SF) varies between 15 and 50%. It is not known whether this incidence depends on the subtype of SF. The recent simplification of the method of measurement of U-citrate (Boehringer-Mannheim kit) led us to address this issue in 118 male idiopathic (I) SF, with either idiopathic hypercalciuria of the renal (n = 6), absorptive (n = 19) or dietary (n = 41) type, or with normocalciuria (n = 52). Results were compared with those of 42 normal male volunteers. 9 patients had hypocitraturia (less than 215 mg/24 h), all of whom belonged to the group of normocalciuric ISF; only this group of patients had mean U-citrate X V significantly lower than controls (p = 0.025). The cause of hypocitraturia in these patients remains unknown: there were no significant correlations between U-citrate X V and U-pH or blood HCO3 or Cl. Moreover, the patients with hypocitraturia had neither urinary infection nor signs of distal tubular acidification dysfunction as assessed by fasting morning urinary pH. Extended to our whole population of ISF (250 patients) 75% of whom have idiopathic stone disease, it appears that measurement of U-citrate decreased the number of ISF without detectable disorder from 34 to 26, i.e. to 10% of the whole population of stone formers. Since hypocitraturia can easily be corrected by oral administration of citrate, routine measurement of U-citrate in normocalciuric ISF appears a promising method.