Login to Access Video or Poster Abstract: MP95-16
Sources of Funding: None

Introduction

Over the past two decades, the prevalence of kidney stones in black non-Hispanics has increased by 150%, yet there is a paucity of literature regarding African American (AA) stone-formers. Small studies suggest certain urinary parameters do not significantly differ between racial groups. We asked whether AA stone formers have any meaningful differences in urine and serum metabolic parameters when compared to Caucasians (C).

Methods

AA patients with known stone composition undergoing metabolic stone evaluation (at least three 24-hour urine collections per patient and paired serum studies) were retrospectively identified by self-reported race from 1995-2016 and sex and age-matched 1:2 to C patients with known stone composition from the same years. Metabolic data were compared between groups by stone type and race using ANOVA. Majority stone type was defined as >50% of composition._x000D_

Results

Fifty-five AA (calcium oxalate (CaOx)=29, Ca phosphate (CaP)=9, Uric acid=17) and 125 matched C (CaOx=81, CaP=27, Uric acid=17) had complete pre-treatment metabolic data. Despite similar supersaturation (SS) for their stone type, AA had significantly lower 24-hr urine volumes than C (1.5 vs. 1.9L, p<0.001). Likewise, 24-hr calcium (Ca) levels, were significantly lower than those for C (135 vs. 225 mg, p<0.0001). Urine oxalate and citrate did not differ by ANOVA. Significant differences between races persisted in volume when analyzed by stone type. CaOx AA had lower urine Ca than C, but oxalate and citrate excretions did not differ. Urine Ca did not differ for CaP stone formers by race. For uric acid stones, AA had lower uric acid excretion and uric acid SS but higher urine pH. Serum phosphate also differed by race, and was lower in AA males than in C males; for women this did not differ.

Conclusions

While physical chemistry dictates that SS drives risk for stone formation, we demonstrate racial differences in determinants of SS. Previously unknown and significant metabolic differences exist between AA and Caucasian stone formers.

Funding

None