Comparison of Hispanics to Caucasians in Metabolic Evaluation of Nephrolithiasis

Abstract

Introduction
It is well-known that nephrolithiasis is related to urinary metabolic abnormalities. However, it is not known what, if any, difference exists between Caucasians and Hispanics in regards to metabolic stone disease. The Southwest United States offers a unique patient population to compare these two groups.
Materials and Methods
A retrospective study was performed at a single institution of all patients that underwent 24 hour urine stone risk studies over a 5-year
period. All urine studies were performed by Litholink. Age, ethnicity, BMI, 24 hour urine parameters, serum electrolytes, Parathyroid
hormone (PTH ) level and stone composition were evaluated. Ethnicity was determined by patient self-selection. Patients that did not
select Hispanic or Caucasian were excluded. Differences in the metabolic evaluation of these patients in regards to the risk of neph
rolithiasis were analyzed.
Results
A total of 208 patients with 349 urine studies were included in the study. There were 122 Caucasians (Group A) and 87 Hispanics
(Group B) with 206 and 143 urine studies respectively. BMI was not statistically different between Group A (28.3) and Groups B
(29.1), p=0.4. However, there were more women in Group B (64.4%) than Group A (50%). Group A had significantly higher urinary
volume, oxalate, potassium, phosphorus, sulfate, urine urea nitrogen and 24 hour creatinine compared to Group B but lower urinary
citrate, supersaturation of calcium phosphate and magnesium levels. Group B had higher PTH compared to Group A (69.7 vs. 42.6,
respectively, p=0.048). Group B also had a higher percentage of Calcium phosphate stones.
Conclusion
Our results suggest that there is a difference in metabolic evaluation between Caucasians and Hispanics. Caucasians have an increased
risk of stone formation due to increased oxalate excretion while Hispanics demonstrate increased risk due to lower urinary volumes
and elevated supersaturation of calcium phosphate.