AP (CAOX) index and calcium/citrate ratio may represent useful tools to assess the risk of crystallization in pediatric renal lithiasis

Abstract

Introduction: Renal lithiasis is a complex process in which not only metabolic abnormalities but interaction among solutes concentrations play a major role. Several tools have been developed in order to quantify the risk of crystallization but there is little information about clinical utility in children. We have explored calcium/citrate ratio and AP(CaOx) index in stoneforming children (SF) and in healthy children (HC). Material and methods: 24-h urine was collected from 87 HC and 14 SF. Pharmacological treatments were discontinued 3 days before analysis. Urine volume, calcium, magnesium, phosphate, urate, citrate and oxalate were determined. Calcium/creatinine, citrate/creatinine, calcium/citrate, and AP(CaOx) index were calculated. Results: We found significant differences between HC and SF regarding calcium concentration (P50 7.2 mg/dl; P25-P75 4.5-12 vs 21; 9.9-26.5, p < 0.001), calcium/creatinine (0.08 mg/mg; 0.05-0.11 vs 0.16; 0.15- 0.23, p < 0.001), citrate/creatinine (542 mg/g; 367-724 vs 385; 188- 613, p = 0.05), calcium/citrate (0.15 mg/mg; 0.09-0.24 vs 0.45; 0.32- 1.13, p < 0.001) and AP(CaOx) (0.55; 0.33-0.83 vs 1.33; 0.81-1.81, p < 0.001). Nevertheless, most of SF had calcium/creatinine and citrate/creatinine values in normal range (calcium/creatinine >0.21 mg/mg, 3/14 patients, citrate/creatinine <250 mg/g, 4/14), but calcium/citrate >0.33 mg/mg was observed in 11/14 patients. Conclusions: Most of SF had calciuria and citraturia in normal range but calcium/citrate and AP(CaOx) index showed significant differences between SF and HC. Calculation of risk formulas may be supplementary useful tools for decision making in the evaluation of the stone-forming patients. Higher values of.