Back to Program


Diabetic stone-formers excrete greater amounts of urine oxalate and have lower urine pH than non-diabetic stone-formers
Brian H. Eisner, MD1, Sima P. Porten, MD2, Seth K. Bechis, MD2, Marshall L. Stoller, MD2.
1Massachusetts General Hospital, Boston, MA, USA, 2University of California, San Francisco, San Francisco, CA, USA.

BACKGROUND: The epidemiologic relationship between nephrolithiasis and type 2 diabetes mellitus is well-known. Patients with diabetes mellitus are at increased risk for nephrolithaisis and those with nephrolithiasis are at risk for developing diabetes mellitus. Diabetic patients are at increased risk for uric acid nephrolithiasis, but it is unknown whether they are also at increased risk for calcium stone formation.
METHODS: We performed a retrospective review of a database of 462 stone-forming patients to examine the relationship between hypertension and 24-hour urine composition. Multivariate linear regression models were adjusted for age, race, gender, body mass index, hypertension, relevant medications, and 24-hour urine constituents.
RESULTS: On univariate analysis, diabetic patients had significantly greater urine volume than non-diabetic patients (2.5 l/d versus 2.1/d, p=0.004). Those with diabetes mellitus also excreted less potassium (61.1 mEq/d versus 68.8 mEq/d, p=0.04), less phosphate (0.84 g/d versus 1.0 g/d, p=0.002), creatinine (1405.5 mg/d versus 1562.8 mg/d, p=0.03), and had significantly lower urine pH (5.78 versus 6.09, p<0.001) and SSCaP (0.49 versus 1.20, p<0.001) than not diabetic patients. On multivariate analysis, compared to patients without diabetes mellitus, those with type II diabetes mellitus had significantly lower urine pH (-0.34, 95% CI -0.48 to -0.21) and had significantly greater amounts of urine oxalate (6.43 mg/day, 95% CI 1.26 to 11.60) and volume (0.38 l/d, 95% CI 0.13 to 0.64).
CONCLUSIONS: This study demonstrates that among stone formers, patients with type II diabetes mellitus excreted significantly greater amounts of urinary oxalate and significantly lower urine pH than those without diabetes mellitus. Thus, it appears that the urine of diabetic paitents may put them at increased risk for uric acid calculi and calcium oxalate calculi. Knowledge of these findings is important in the treatment of patients with nephrolithiasis as it may influence dietary counseling, medical management, and stone prevention.


Back to Program