Comparison of the Metabolic Profile of Mixed Calcium Oxalate/Uric Acid Stone Formers to That of Pure Calcium Oxalate and Pure Uric Acid Stone Formers
OBJECTIVE To compare the metabolic profile of patients who form mixed calcium oxalate (CaOx)/uric acid (UA) stones to those of pure CaOx and pure UA stone formers. METHODS We performed a retrospective review of 232 patients, with both stone composition analysis and 24-hour urine collection, seen between March 2002 and April 2012. Analysis of 24-hour urine constituents across the 3 stone groups (pure UA, pure CaOx, and mixed CaOx/UA) was performed using univariate analysis of variance and multivariate linear regression models adjusting for clinical and demographic factors and 24-hour urine collection elements. RESULTS A total of 27 patients (11.6%) had mixed CaOx/UA, 122 (52.6%) had pure CaOx, and 83 (35.8%) had pure UA calculi. Univariate analysis demonstrated significant differences between mixed CaOx/UA patients and pure CaOx patients for urine pH (mixed, 5.63 +/- 0.49 vs pure, CaOx 5.93 +/- 0.51; P = .009) and supersaturation (SS) UA (mixed, 1.84 +/- 1.09 vs pure, CaOx 1.26 +/- 0.93; P = .01), and a significant difference between mixed CaOx/UA patients and pure UA patients for SS CaOx (mixed, 7.18 +/- 4.23 vs pure, UA 4.90 +/- 2.96; P = .005). Multivariate analysis demonstrated that mixed CaOx/UA patients had no significant difference in SS CaOx as compared with pure CaOx patients (difference, -0.27; P = .66), whereas at the same time had no significant difference in SS UA as compared with pure UA patients (-0.07; P = .69). CONCLUSION The metabolic profile of patients who form mixed CaOx/UA stones demonstrates abnormalities that promote both CaOx and UA stone formation. Dietary and medical management for this group of patients should address treatment of both defects. (C) 2014 Elsevier Inc.
Faculty, Northwell Researcher
School of Medicine; Northwell Health