Login to Access Video or Poster Abstract: MP19-03
Sources of Funding: None

Introduction

Recent studies have demonstrated associations between nephrolithiasis and systemic conditions, including low bone mineral density (BMD), which may be correlated to hypercalciuria in these kidney stone formers (KSF). Traditionally, low bone mineral density is diagnosed with dual-energy x-ray absorptiometry. Our objective was to evaluate the association of CT-based vertebral bone mineral density with 24-hour urine parameters in KSF

Methods

This is a retrospective analysis of 99 kidney stone formers who had CT imaging and 24-hour urine studies at our institution. For each patient, BMD was estimated by placing an oval region of interest on an area of vertebral body trabecular bone at the L1 level and CT attenuation measured in Hounsfield units (HU). From established data, a threshold for a balanced sensitivity (73.9%) and specificity (70.6%) of 160 HU was chosen to distinguish normal from low BMD. Patient demographics, serum chemistry, and 24-hour urine parameters were collected for each patient. Univariate and multivariate logistic regression analysis was performed to compare patients with low and normal BMD. Multivariate linear regression was performed to assess for variables associated with 24-hour urine parameters. _x000D_ _x000D_

Results

Compared to patients with normal BMD, patients with low BMD were older (67 vs 50 yrs, p<0.0001), were male (69% vs 34%, p=0.001), had HTN (81.8% vs 24.7%, p<0.0001), underwent percutaneous nephrolithotomy (20% vs 0%, p=0.003), had higher 24-hour urine calcium (219 vs 147, p<0.0001), increased visceral fat area (251 vs 179 cm², p=0.003) and had larger stone volume (259 vs 78.4 mm³, p=0.009). Multivariate analysis revealed older age (p=0.004) and elevated urine calcium (p=0.0002) correlated with low BMD. Linear regression demonstrated that lower BMD was associated with higher urine calcium (-coefficient 0.247, p=0.020) and lower urinary citrate (-coefficient 0.331, p=0.009).

Conclusions

CT-based diagnosis of low mineral bone density is associated with derangement in 24-hour urine calcium and citrate in kidney stone formers, as well as larger stone volumes. _x000D_

Funding

None