Clinical and Metabolic Correlates of Pure Stone Subtypes

Abstract

Background: There are multiple stone types, each forming under different urinary conditions. We compared clinical and metabolic findings in pure stone formers to understand if there are consistent factors that differentiate these groups in terms of underlying etiology and potential for empiric treatment. Materials and Methods: Pure SFs based on infrared spectroscopic analysis of stones obtained at our institution between 01/2002 and 07/2018 with a corresponding 24-hour urinalysis were retrospectively evaluated. Results: 121 apatite, 54 brushite, 50 calcium oxalate dihydrate, 104 calcium oxalate monohydrate, and 82 uric acid patients were analyzed. Apatite, brushite, and calcium oxalate dihydrate patients were younger than calcium oxalate monohydrate and uric acid patients. Uric acid patients had the highest male predominance (76.8%), while apatite patients were predominantly female (80.2%). Uric acid was most associated with diabetes mellitus (45.3%), and calcium oxalate monohydrate with cardiovascular disease (27.2%) and malabsorptive gastrointestinal conditions (19.2%). Brushite patients had the highest prevalence of primary hyperparathyroidism (17%). Apatite, brushite, and calcium oxalate dihydrate patients demonstrated high rates of hypercalciuria (66.1%, 79.6%, 82%). Apatite and brushite patients had the highest urinary pH. Apatite patients exhibited the highest rate of hypocitraturia while calcium oxalate dihydrate patients exhibited the lowest (55.4%, 30%). Calcium oxalate monohydrate patients had the highest rate of hyperoxaluria (51.9%). Uric acid patients had the lowest urinary pH. There were no observable differences in the rates of hyperuricosuria or hypernatriuria. Conclusions: These results demonstrate that pure stone composition correlates with certain urinary and clinical characteristics. This data can help guide empiric clinical decision-making.