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Abstract: PO0600

Body Mass Index (BMI) and Kidney Stone Risk in Calcium Kidney Stone Formers

Session Information

Category: Bone and Mineral Metabolism

  • 402 Bone and Mineral Metabolism: Clinical

Authors

  • Tang, Jie, Brown University Warren Alpert Medical School, Providence, Rhode Island, United States
  • Bhetuwal, Uttam, Lifespan Health System, Providence, Rhode Island, United States
Background

The role of obesity among calcium kidney stone formers remains poorly defined, and it is unknown whether there are effect modifications of stone risk by diabetes and insulin resistance (IR).

Methods

We examined the independent associations between BMI and 24-hour urine stone risk profile among 167 calcium kidney stone formers (CSF), and analyzed the effect modifications by diabetes and IR measured by Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) in non-diabetics. Study participants were recruited from Lifespan Kidney Stone Clinic. We used linear regression and adjusted for demographics.

Results

The study population (n=167) had a mean age of 53 years, 77 (46%) were male, and 135 (81%) were Caucasian. 28 (17%) had diabetes. Mean BMI was 29 (Interquartile range (IQR) 25 to 33). Higher BMI associated strongly with diabetes (p<0.0001). Among 139 non-diabetic CSFs, mean BMI was 28 (IQR 25 to 31), and BMI had a strong positive association with HOMA-IR (p=0.001). 33% of nondiabetic CSFs had hypertension (vs. 100% in diabetics), 21% of nondiabetic CSFs had dyslipidemia (vs. 89% in diabetics). HOMA-IR ranged from 0.42 to 28.2 (mean 4.3). Overall, in the whole study population, BMI had significant positive associations with urine ammonium, urine uric acid (UUA), and UUA supersaturation (p= 0.004, <0.0001, <0.0001 respectively). The strong association between BMI and urine ammonium was only observed among diabetics (p=0.006), with a similar trend observed among non-diabetics with high IR (p=0.09 when HOMA-IR>10, p= 0.9 when HOMA-IR= 5-10, p=0.2 when HOMA-IR<5). On the contrary, the uricosuric effect of higher BMI was only observed in nondiabetics who had normal or near-normal IR (p=0.3 among diabetics, p<0.0001 when HOMA-IR<5, p= 0.003 when HOMA-IR=5-10, p=0.5 when HOMA-IR>10). As a result, the UUA supersaturation tended to have weak associations with BMI among diabetics or non-diabetics who had high IR (p=0.09 in diabetics and those with HOMA-IR>10, p= 0.2 when HOMA-IR< 5, p=0.9 when HOMA-IR=5-10). Lastly, BMI did not have significant associations with serum levels of vitamin D and uric acid, plasma parathyroid hormone concentration and measurements of other urinary stone risk factors.

Conclusion

In our cohort of CSFs, higher BMI had strong associations with urinary uric acid and ammonium excretions, and these associations appeared to be modified by the presence of diabetes or IR.

Funding

  • Clinical Revenue Support