METABOLIC EVALUATION OF PATIENTS WITH RECURRENT IDIOPATHIC CALCIUM NEPHROLITHIASIS

Background. Metabolic evaluation in recurrent idiopathic calcium renal stone-formers (RCSF) was analysed with respect to the following quest ions: (1) do three 24-h urines provide more diagnostic accuracy in the metabolic evaluation of RCSF than 1 or 2 urines?; (2) does time after stone event influence the diagnostic yield?; (3) is urine composition at weekends different from that at mid-week?; (4) what are the preval ences of the most important risk factors (RF) of idiopathic calcium ne phrolithiasis, i.e. low volume (LV), hypercalciuria (HC), hyperoxaluri a (HO), hyperuricosuria (HU), hypocitraturia (Hypo-Cit), and hypomagne siuria (Hypo-Mg)?; and (5) do male RCSF differ from females with respe ct to urinary RFs? Methods. Seventy-five RCSF (59 men, 16 women) colle cted three 24-h urines (U1-3) while on free-choice diet. To account fo r possible variations in lifestyle and diet, U1 and U3 had to be colle cted midweek and U2 at a weekend. Results. When considering all three urines together (U1 + U2 + U3), the number of RF abnormalities/patient was 2.8 +/- 0.1, higher than numbers of any combination of two urines or of any single urine (P = 0.0001 for all comparisons). The number o f RF abnormalities also rose with time after stone event, from 0.8 +/- 0.1 (range 0-4) in U1 to 1.1 +/- 0.1 (range 0-4) in U3 (P = 0.011 vs U1). Whereas all other RF did not change between collections, urine vo lume was lower in U2 (1793 +/- 90 ml) than in U1 (2071 +/- 97 ml, P = 0.0001 vs U2) and U3 (1946 +/- 97 ml, P = 0.046 vs U2). At least 1 abn ormality was found in 85.3% of all RCSF, and multiple abnormalities oc curred in 47%. The most frequent RF was HC (39%), followed by HO and L V (32% each), Hypo-Cit (29%), HU (23%) and Hypo-mg (19%). Males more o ften had Hypo-Cit (P< 0.001) and Hypo-Mg (P<0.01) than females, wherea s HO was more frequent in female RCSF (P<0.025 vs males). Conclusions. Diagnostic accuracy of metabolic evaluation in RCSF increases both wi th the number of urines collected and the time passing after a stone e vent. Urines collected at weekends differ from those of the week only by their lower volumes. Abnormalities of RF for calcium nephrolithiasi s can be detected in 85.3% of RCSF, and HC is the most-common RF both in male and female RCSF.