Type-2 diabetes and kidney stones: impact of diabetes medications and glycemic control.

OBJECTIVE

To evaluate the impact of diabetic medications and glycemic control on the urine pH, 24-hour urine stone risk profile, and stone composition.

PATIENTS AND METHODS

We retrospectively reviewed our database searching for type-2 diabetic patients with kidney stones from July 2002 to January 2013. Patients were divided in 2 groups according to their diabetic medications: insulin vs oral antihyperglycemics. Patients were compared based on their urine collections and stone composition. A linear regression was done to assess which variables could predict a low urine pH. In a subgroup analysis, patients on thiazolidinediones (ie, pioglitazone) were compared with patients on other oral antihyperglycemics.

RESULTS

We analyzed 1831 type-2 diabetic patients with stone disease; 375 (20.5%) were included in the insulin group and 1456 (79.5%) in the antihyperglycemics group. Linear regression revealed male gender (P = .011) and insulin therapy (P <.001) as protective factors of low urine pH, whereas HbA1c level (P <.001) was inversely related to the urine pH (odds ratio, -0.066; 95% confidence interval, -0.096 to -0.036; P <.001). There were no significant differences in other 24-h urine stone risk parameters or stone composition between the groups. There were also no significant differences in the subgroup analysis.

CONCLUSION

Urine pH is inversely related to HbA1c level. Insulin therapy is associated with higher urine pH than oral antihyperglycemic agents despite higher HbA1c suggesting that insulin may modify urine pH independent of glycemic control.