Metabolic risk factors in patients with first-time and recurrent stone formations as determined by comprehensive metabolic evaluation.

OBJECTIVES: To determine whether patients with recurrent calcium stone formation have more significant metabolic abnormalities compared with patients with first-time stone formation as determined by a comprehensive metabolic evaluation.
METHODS: We investigated metabolic abnormalities in 37 patients (14 men, 23 women) with first-time and 136 patients (83 men, 53 women) with recurrent calcium stones, stratified according to sex. Calcium oxalate supersaturation indexes of Tiselius (1991) and Ogawa (1996) were also compared between the groups. In addition to the specific metabolic abnormalities, we analyzed the total number of such defects for each group.
RESULTS: In men, the average number of metabolic abnormalities in each patient was greater in patients with recurrent stones (2.20+/-0.86) than in those with first-time stones (1.46+/-1.27). Such a difference could only be demonstrated for women if low urine volume was excluded as a specific abnormality. Although the frequency of each abnormality was higher in patients with recurrent stones, a statistically significant difference was only noted in the frequency of hypocitraturia between women with first-time and recurrent stone formation (11.1% versus 37.8%, P < 0.05). There were no significant differences in the calcium oxalate supersaturation indexes between first-time and recurrent stone formation in either men or women.
CONCLUSIONS: Women with recurrent stones have a higher prevalence of hypocitraturia than women with first-time stones. Potassium citrate therapy for prevention of urolithiasis may be especially useful for this patient population.