Best Practices & Benign Disease
Introduction & Objective : Kidney Stone Incidence has been known to vary with temperature and climate. But very little is known about any variation in the composition of kidney stones across different regions of the United States. We attempted to evaluate whether stone composition changes depending on region.
Methods : We were given access to de-identified data from LABCORP’s database of kidney stone composition from 8/1/2016 and 10/24/2016 for states in 7 representative areas of the country: Virginia, Minnesota, Florida, Arizona, Colorado, Florida and Texas. We analyzed each component of kidney stones with optical microscopy supplemented with FT-IR spectrometry using both the percentage of the stone that was composed of that component (a continuous variable), as well as a binary variable coded none versus any. Univariate associations between component and state were examined using chi-square or Fishers Exact Test for the binary indicator, and analysis of variance for the continuous percentage (using the log-transformed percentages if they were non-normal). The same set of analyses was used for decade of age versus each component. The association between age and state was examined using analysis of variance.
Results : Data were available for 4335 kidney stones, from patients in the 7 states mentioned. The most common components across all stones were Calcium Oxide Monohydrate and Calcium Phosphate (both present in 93% of stones), Calcium Oxide Dihydrate (in 57% of stones), and uric acid (in 12% of stones). Stone composition did not vary widely across regions except for uric acid stones which were more prevalent in Florida compared to other states, with an OR of 1.43 (95% CI 1.12-1.83)
Kidney Stone composition does not vary widely by region within the United States. While temperature and humidity play a role in stone incidence, there does not appear to be a large variation between different climates with the exception of uric acid stone formation in Florida.