Metabolic risk factors and urinary stone formation. Study II: the effect of phosphaturia and magnesiumuria

Golovanov S.A., Sivkov A.V., Drozhzheva V.V., Anohin N.V.

Elevated excretion of inorganic phosphates (more than 33.6 mmol/ day) and magnesium (more than 5.1 mmol/ day) increased the risk of oxalate stone formation in patients with urolithiasis (200 males and 237 females, aged from 16 to 75). Phosphaturia and magnesiumuria were accompanied by the rise in the level of calcium and uric acid excretion and the increase in urine acidity, which, presumably, are the additional factors, which promote oxalate lithogenesis.

In patients with hyperphosphaturia and hypermagnesiumuria, the risk of carbonate apatite and struvite stone formation decreased twofold and 3-4-fold, respectively, in comparison with patients, who had lower levels of phosphate and magnesium excretion.

Phosphaturia and magnesiumuria had similar influence on oxalate stone formation. The increase in oxalate lithogenesis was observed in patients with elevated levels of phosphaturia (r = 0.759; р=0.0108) and magnesiumuria (r=0.7862; р=0.007). The increase in phosphaturia was followed by a relatively equal decrease in the incidence of carbonate apatite stone detection (r = -0,724; р=0,0178). On the contrary, magnesium excretion at the level of 0.3-5.2 mmol/day had a U-shaped diverse effect on carbonate apatite stone formation. Magnesium excretion at the level of 0.3-3.5 mmol/day correlated with the reduction in the incidence of carbonate apatite stone formation from 40.7% to 15.0% (p=0.002). The increase in magnesiumuria from 3.5 to 5.2 mmol/ day was followed by the rise in the incidence of apatite stone formation from 15.0% to 34.2% (p=0.0049).

In patients with urolithiasis, the incidence of calcium oxalate-phosphate stone formation did not depend on the intensity of phosphaturia but had a positive correlation with the severity of magnesiumuria (r = 0.651; р = 0.041). No remarkable influence of hyperphosphaturia and hypermagnesiumuria on the risk of urate stone formation was found. In patients with urolithiasis, the incidence of urate stone detection did not depend on the intensity of magnesiumuria but had a direct correlation with the severity of phosphaturia (r = 0.749; р=0.0127).

Our data indicates that the influence of phosphate and magnesium excretion on the frequency and risk of urinary stone formation of a particular metabolic type has complex character. The rates of phosphate and magnesium excretion may be used for the prognosis of urinary stone formation of a particular mineral composition and can be applied for the selection of relevant methods of anti-relapse treatment, taking into account any other accompanying metabolic disorders.

Authors declare lack of the possible conflicts of interests

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urilithiasis, phosphaturia, magnesiumuria, stone formation, metabolic risk factors

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