A high basal metabolic rate is an independent predictor of stone recurrence in obese patients

Basal metabolic rate (BMR) is an indicator of overall body metabolism and may portend unique aberrations in urine physico-chemistry and stone recurrence. The present study examined the effect of predicted BMR on 24 hours urinary metabolic profiles and stone recurrence in obese stone patients.

Data from 308 obese patients (body mass index [BMI] ≥30 kg/m²) diagnosed with urinary stone disease between 2003 and 2015 were analyzed retrospectively. BMR was calculated using the Harris-Benedict equation, and patients were classified into two predicted BMR categories (<1,145 kcal/day, ≥1,145 kcal/day). Urinary metabolic parameters and risk of stone recurrence were compared between the two groups.

The high BMR group was more likely to be younger and female, and to have a high BMI and lower incidence of diabetes than the low BMR group (each p<0.05). There was a positive correlation between BMR and 24 hours urinary sodium, uric acid, and phosphate excretion. The amounts of stone-forming constituents such as calcium and uric acid were significantly higher in the high BMR group. Kaplan-Meier estimates showed that the high BMR group had a significantly shorter stone recurrence-free period than the low BMR group (log-rank test, p<0.001). Multivariate Cox regression analyses revealed that predicted BMR was an independent factor of stone recurrence (hazard ratio, 2.759; 95% confidence interval, 1.413-5.386; p=0.003).

BMR may be an easily measured parameter that can be used to identify risk of stone recurrence in obese stone patients.