[Risk factors for the formation of urinary calcium-containing stones in diabetics]

Levels of 24-hour urinary calcium, magnesium, oxalate, citrate, uric acid, phosphorus and creatinine as well as urinary volume were determined in 85 patients and 81 normal subjects. Among the patients, 43 were diabetics without stone, 5 diabetics with stone and 37 with idiopathic calcium stone formation in the urinary tract. It is shown that the main risk factors involved in urinary calcium-containing stone formation are the levels of calcium, oxalate, uric acid and citrate and the volume of 24-hour urine. With the data obtained, the authors calculated the ion-activity products index of calcium oxalate and the relative probability of stone formation in the three groups of patients and the control group of normal subjects. The index in normal subjects, diabetics without stone, diabetics with stone and patients with idiopathic urinary calcium stone was 3.07 +/- 0.16, 2.90 +/- 0.25, 3.90 +/- 0.58 and 5.11 +/- 0.38 respectively. The upper limit of the relative probability in normal subjects was 0.54. Most of the patients with idiopathic urinary calcium stone (32/37) and all the 5 diabetics with stone had higher probability value than this, while most of the normal subjects (73/81) and of the diabetics without stone (39/43) had value lower than this. The results indicate that though the diabetics have higher level of urinary calcium and higher value of the product of calcium x oxalate x uric acid, they have also inhibitive factors for stone formation, such as increased level of urinary citrate. As a result, urinary stone formation will not be a frequent occurrence.