Metabolic risk factors and urinary stone formation

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

We have examined mineral composition of 437 urinary con-crements obtained from 200 men and 237 women. The levels of daily urinary excretion of calcium and uric acid were also analyzed. We have shown that the increase of calcium excretion (more than 6.6 mmol per day) increases the incidence of oxalate stone formation. In this case, the relative risk index was 1.76, in comparison with patients, whose level of calcium excretion was less than 2.6 mmol per day (-p=0. 0018)

The incidence of oxalate and oxalate-phosphate stone formation correlates with the increase in calciuria. The most remarkable increase in the incidence of these types of stones is observed in patients with calcium excretion of more than 5 mmol per day. This level can be regarded as a calciuria threshold, suggesting the beginning of the corresponding metaphy-laxis. The risk of struvite stone formation decreases in patients with calcium excration of more than 6.6 mmol per day, in comparison with those, who have low level of calciuria (RR index = 0.19; p = 0.0081). The degree of calciuria does not affect the rate of calcium-phosphate (carbonate-apatite) stone formation.

Hypercalciuria of more than 6.6 mmol per day is followed by the decrease in the risk of urate stone formation by 2.2 (RR index = 0.46; p = 0.0118), notwithstanding the accompanying hyperuricuria and more acidic urine.

Hyperuricuria of more than 4.2 mmol per day leads to the increase in the rate of calcium-oxalate stone formation in patients with urolithiasis (RR index = 1.35, p = 0.0468), which can be promoted by the accompanying hypercalciuria (up to 6.43 ± 0.23 mmol per day). Lithogenic effect of uric acid is divergent and depends on the intensity of its excretion. Growing uricuria (up to 4.3 mmol per day) may promote the formation of urate stones (the incidence of these stones elevated from 21.6% to 42.1%, p <0.05). However, uricuria of more than 4.3 mmol per day mostly stimulates the formation of oxalate stones (the incidence of these stones raised from 31.6% to 50.0%, p <0.05). In this case, the incidence of urate stones reduced from 42.1% до 14.6% (p <0.05).

The data obtained points to the diversity of lithogenic effects of urine-excreted urates and calcium in patients with urolithiasis. In addition to accompanying metabolic disorders, this should be taken into consideration, when one is prescribing an adequate antirecurrence therapy.

Authors declare lack of the possible conflicts of interests.

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urolithiasis, metabolic risk factors, formation of urinary calculi, calciuria, uricuria