Abnormalities of 24-Hour Urine Composition in First-time and Recurrent Stone-formers

ObjectiveTo examine differences in 24-hour urine composition between recurrent and first-time stone-formers.MethodsA retrospective review of patients evaluated in 2 metabolic stone clinics was performed. Recurrent stone formation was defined as patients with a history of more than 1 stone episode and first-time stone-formers were those with a history of a single-stone episode. Frequencies of urine metabolic abnormalities were noted. Multivariate linear regression was performed to evaluate the likelihood of abnormalities of 24-hour urine composition.ResultsThree-hundred eleven patients met inclusion criteria: 71 (22.8%) were first-time stone-formers and 240 (77.1%) were recurrent stone-formers. On univariate analysis, the likelihood of having a single abnormality of 24-hour urine composition (ie, hypercalciuria, hyperoxaluria, hyperuricosuria, or hypocitraturia) was similar between the 2 groups (83.1% for first-time vs 88.8% for recurrent, P = NS). In addition, there were similar rates of hypercalciuria (39.4% vs 43.3%, P = NS), hyperoxaluria (32.4% vs 33.3%, P = NS), hyperuricosuria (29.6% vs 23.3%, P = NS), and hypocitraturia (45.0% vs 45.0%, P = NS). On multivariate logistic regression, there was no difference in detection of any urine abnormality (ie, hypercalciuria or hyperoxaluria or hypocitraturia or hyperuricosuria) between first-time (referent) or recurrent stone-formers (OR 1.68, 95% CI .8-3.5, P = .2).ConclusionIn this study, detection of urine abnormalities was similar in first-time and recurrent stone-formers. Given the strong patient preference for stone prevention and the high success of directed therapy in the literature, we believe it is not unreasonable to offer comprehensive metabolic evaluation to first-time stone-formers who express a desire to undergo evaluation.