International Urology and Nephroloyy 21 (4), pp. 369-- 373 (1989) On the Relation between Citrate and Calcium in Normal and Stone-former Subjects A. Com'E,* P. RocA,** M. GIANOTTI,*** F. GRASES+ * Servei d'Urologia, Hospital General "Virgen de Lluc" (Insalud); Departaments de +Quimi- ques, **Matemhtiques i Inform~ttica, ***Biologia i Ci6ncies de la Salut, l'Universitat de les Illes Balears, Palma de Mallorca, Spain (Received May 20, 1988) The aim of this work is to evaluate citrate in a group of patients with calcium oxalate urolithiasis and in a control group for detecting possible differences between the two groups. The mean urinary concentration in groups o f stone-formers was found signi- ficantly lower than in the control group. Particularly interesting was the correlation study between citrate and calcium. It was found that patients with hypocitraturia have hypercalciuria. Thus, it is particularly interesting to point out the importance of citrate in preventing the risk of lithiasis in stone-formers studied by us. Introduction The importance of citrate in nephrolithiasis stems from the apperception that citrate is a direct inhibitor of calcium phosphate precipitation [1 ] and calcium oxalate crystal growth [2]. The ability of citrate to form soluble complexes with divalent cations, such as calcium, is well known. Such complexation may cause some reduction in the urinary saturation of "stone forming" calcium salts. Be- cause of these facts urinary citrate concentrations may hax e important implications in renal stone formation. Several reports claim that idic)pathic stone-formers excrete significantly less citrate in their urine than normal subjects [3-12]. Others, however, have not con- firmed this difference [13-16]. One of the problems with citrate excretion is that it depends on age and sex; it changes with age [17] and is generally higher in women than in men [3, 4, 6, 13, 17]. The measurement of urinary excretion of citrate is clearly useful in the management of stone disease in some patients, in identifying certain disease states that result in hypocitraturia. Thus, although citrate has been reported to be effective in some cases of idiopathic renal lithiasis, this dees not establish whether the low citrate excretion rate was pathogenetic, or the response was caused by increasing urinary citrate levels [18]. + To whom correspondence should be addressed. 2* VSP, Utrecht Akad6miai Kiad6, Budapest