#1834 Prevalence of nephrolithiasis in patients with idiopathic hypercalciuria after two decades of follow-up

Abstract

Abstract Background and Aims Idiopathic hypercalciuria (IH) is the main metabolic abnormality that causes kidney stones. It is linked to high intestinal calcium absorption and osteopenia. However, not all patients diagnosed with IH develop kidney stones. In this study, we examined a cohort of patients diagnosed of IH during childhood to determine the prevalence of lithiasis in adulthood. Method Longitudinal study that evaluated the prevalence of lithiasis in 35 patients (12 female, 23 male) diagnosed of IH during childhood (mean age of 7.7 ± 3 years). The patients were followed until adulthood (mean age 28.2 ± 3.1 years) with a median follow-up of 18.2 years (IQR: 12.2-19.3). IH diagnosis was made by urinary calcium excretion higher than 4 mg/Kg/day in two consecutive samples. In both periods, clinical and demographic data were collected, including urinalysis and urinary ratios (calcium/creatinine, calcium/citrate, oxalate/creatinine, and citrate/creatinine) in an isolated sample of the first morning urine, as well as the performance of renovesical ultrasound. Results In pediatric age, 8 patients (26%) presented nephrolithiasis on ultrasound, and 14 (43.8%) in adulthood, 6 of them experiencing episodes of nephritic colic. During the study, we observed a decrease in urinary calcium excretion, as expressed by the calcium/creatinine ratio (adult age 0.16 ± 0.9 mg/dl vs. childhood 0.28 ± 0.1 mg/dl, p = 0.000), and an hypocitraturia increase (citrate/creatinine ratio in childhood 887 ± 349 mg/dl and in adulthood 357.7 ± 363 mg/dl, p = 0.000). A decreased citrate/creatinine ratio in adulthood was associated with nephrolithiasis (p < 0.007). Only 4 patients (50%) had nephrolithiasis at both ages. Conclusion These results suggest that hypercalciuria tends to correct spontaneously in adulthood, and although the prevalence of nephrolithiasis increased, it is more related to hypocitraturia.