Ethnic background has minimal impact on the etiology of nephrolithiasis.
OBJECTIVE
Nephrolithiasis disproportionately affects white patients. However, recent studies propose an increase in the incidence of stone disease in nonwhite populations. We compared the metabolic risk factors of ethnically disparate stone formers from the same geographic region.


METHODS
A retrospective review of 1,141 patients identified 98 (9%) nonwhite stone formers. Of these individuals 60 underwent a comprehensive metabolic evaluation, comprising 44 black, 8 Asian and 8 Hispanic patients. A similar sex and age matched group of 66 white stone forming patients were also identified for comparative analysis. Stone analyses were recorded when available. Urinary metabolic abnormalities were defined as low urine volume-urine volume less than 2,000 cc, gouty diathesis-pH 5.5 or less (normal level 5.5 to 6.5), hypercalciuria-calcium greater than 200 mg, hyperoxaluria-oxalate greater than 45 mg, hyperuricosuria-uric acid greater than 600 mg, hypocitraturia-citrate less than 600 mg and purine gluttony-sulfate greater than 20 mg.


RESULTS
The incidence of metabolic abnormalities was surprisingly similar between the white and nonwhite stone formers. Whites have a higher prevalence of hypercalciuria compared with nonwhites (67% vs 25%, respectively, p <0.01). This comparison persisted when the white group was compared with individual ethnic groups (25% in each group). Whites also displayed a higher mean urinary calcium level (233 mg) than their nonwhite counterparts overall (146 mg), specifically with respect to blacks (146 mg, p <0.01). Asians had higher urine volumes with respect to whites and blacks (p <0.01) and, therefore, a decreased prevalence of low urine volumes (37.5% vs 74.2% and 79.5%, respectively). Hypocitraturia, hyperuricosuria, hyperoxaluria, gouty diathesis and high sulfate levels were equally represented among all ethnic groups.


CONCLUSIONS
Although there appears to be a predominance of stone disease among whites, all racial groups demonstrated a remarkable similarity in the incidence of underlying metabolic abnormalities. These results suggest that dietary and environmental factors may be as important as ethnicity in the etiology of stone disease.
Maloney
Michaella E
ME
Comprehensive Kidney Stone Center, Division of Urology, Department of Surgery, Duke University Medical Center, Durham, North Carolina, USA.
Springhart
W Patrick
WP
Ekeruo
Wesley O
WO
Young
Matthew D
MD
Enemchukwu
Chibuzo U
CU
Preminger
Glenn M
GM
D000328:Adult; D000368:Aged; D002118:Calcium / Q000652:urine; D019343:Citric Acid / Q000652:urine; D003430:Cross-Sectional Studies; D005006:Ethnicity / Q000706:statistics & numerical data*; D005260:Female; D006073:Gout / Q000453:epidemiology / Q000208:ethnology / Q000209:etiology; D006801:Humans; D006959:Hyperoxaluria / Q000453:epidemiology / Q000208:ethnology / Q000209:etiology; D015994:Incidence; D007669:Kidney Calculi / Q000453:epidemiology / Q000208:ethnology* / Q000209:etiology; D008297:Male; D008875:Middle Aged; D012008:Recurrence; D012189:Retrospective Studies; D012307:Risk Factors; D013431:Sulfates / Q000652:urine; D014527:Uric Acid / Q000652:urine; D014563:Urodynamics / Q000502:physiology; D044465:White People / Q000706:statistics & numerical data
D013431:Sulfates; D014527:Uric Acid; D019343:Citric Acid; D002118:Calcium