Login to Access Video or Poster Abstract: MP01-11
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Introduction

Prior studies have demonstrated links between uric acid stone risk and low urine pH, visceral fat area (VFA) and the ratio of visceral to subcutaneous adipose tissue (VFA%). Our objective was to assess the association of CT-based visceral obesity with 24-hour urine metabolic risk factors stone composition in kidney stone formers (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, a single axial area measurement was obtained at L3-4 in females and L2-3 in males for visceral fat area (VFA) and subcutaneous fat area (SFA). Percentage of visceral fat was calculated with the formula VFA%=[VFA/(VFA+SFA)] X 100. From established data, a VFA > 186 cm² was considered elevated in terms of risk of nephrolithiasis. Patient demographics, serum chemistry, 24-hour urine parameters and stone composition were collected for each patient. Univariate analysis was performed to compare patients with normal and elevated VFA. Multivariate linear and logistic regression was performed to assess for variables associated with 24-hour urine parameters and stone composition. _x000D_ _x000D_

Results

Compared to patients with normal VFA, patients with high VFA were older (65 vs 51 yrs, p<0.0001), more obese (BMI 33.3 vs 28, p=0.02) and were male (70.7% vs 30%, p=0.001). They also had higher prevalence of HTN (81% vs 45%, p<0.0001), DM (31% vs 12.5%, p=0.003), CAD (32.8% vs 7.5%, p=0.003). Higher VFA was associated with higher urinary sodium (175 vs 157 mmol/d, p=0.036), lower urine pH (5.724 vs 6.478, p<0.0001), higher serum uric acid (6.6 vs 5.3, p=0.002), higher prevalence of uric acid stones (15.5% vs 2.5%, p=0.031), lower bone mineral density (146 vs 168 HU, p<0.0001) and larger stone volume (256 vs 67 mm³, p=0.009). Multivariate analysis revealed higher BMI (p=0.009), coronary artery disease (p=0.027) and lower 24-hour urine pH (p=0.001) correlated with elevated VFA. 24-hour urinary citrate (p=0.031) and higher VFA (p=0.048) correlated with uric acid stone formation. Linear regression demonstrated that a higher VFA% was associated with lower 24-hour urine pH (β-coefficient -0.574, p=<0.0001)

Conclusions

CT-based diagnosis of elevated visceral fat area is associated with lower 24-hour urinary pH and formation of uric acid calculi. Evaluation for visceral obesity may help identify patients best suited for alkalinization and dissolution therapy. _x000D_ _x000D_

Funding

none