Introduction. The role of magnesiuria as a metabolic factor in the lithogenesis of both calcium stones and separately oxalate and phosphate urinary stones, as well as stones of other metabolic types, remains unclear. In this work, we investigated the effect of the degree of magnesium excretion in men and women with urolithiasis on metabolic parameters and the frequency of detection of urinary stones of various chemical compositions.
Materials and methods. 865 stone formers (392 men and 473 women aged 18 to 79 years) were examined. To assess the lithogenic activity of magnesiuria in stone formers men and women, the values of magnesium excretion (in mmol/day) were ranked in ascending order and divided into 10 equal parts. The percentage distribution of urinary stone types and biochemical parameters of urine and blood were determined in each range.
Results. As magnesiuria increased, the proportion of calcium oxalate stones among male patients increased 2.0-2.7 times (p=0.0001), the frequency of detection of oxalate stones increased 1.7 times (p=0.009), in contrast to women. In women, the proportion of carbonate apatite stones increased 2.0-4.0 times (p=0.025), and the frequency of detection of phosphate stones from carbonate apatite with increasing magnesiuria was 2.0 times higher than in men (p=0.001). In men, an increase in magnesium excretion was accompanied by an increase in the frequency of detection of calcium stones by 1.6-2.0 times (p<0.025) and there was a direct correlation between magnesiuria and the frequency of detection of calcium stones (rs = 0.700, p = 0.036), in contrast to women. However, women showed high activity of carbonatapatite lithogenesis, which was almost 2-3 times higher than that of men (p <0.0001). Magnesiuria in women negatively correlated with the frequency of detection of carbonatapatite stones (r= -0.704, p=0.034) and the pH of urine (r= -0.900, p=0.0009). In men, there was no noticeable effect of increasing magnesiuria on the frequency of detection of uric acid stones, whereas in women, there was a 2.2-2.8-fold increase in the frequency of detection of uric acid stones (p<0.04). In patients of both sexes, an increase in magnesiuria was accompanied by a decrease in the incidence of struvite stones, apparently due to acidification of urine, due to the existence of an inverse correlation between magnesiuria and urine pH values (in women rs = 0.783, p = 0.013; in men rs = -0.733, p = 0.025). Compared with women, there was an increase in the proportion of male patients with oxalate stones in the age groups 18-29yr (2.5 times, p=0.0023) and 50-59yr (2.15 times, p<0.0001), indicating the association of magnesiuria with oxalate lithogenesis. At the same time, there was no noticeable effect of magniuria on carbonatapatite lithogenesis.
Conclusion. Magnesiuria has a certain modifying effect on the lithogenesis of oxalate stones, uric acid stones, phosphate (carbonatapatite) and calcium oxalate-phosphate stones. In stone formers men and women, the nature of this effect has its own characteristics. With magnesiuria above 3.0 mM/day, the relative risk of developing oxalate and carbonatapatite stones in men is increased, and the risk of phosphate lithogenesis in women is reduced. The lithogenic properties of magnesiuria are largely able to manifest themselves due to the involvement of other lithogenic factors in the process of stone formation, such as calciuria and/or shifts in urine pH. what should be considered when conducting personalized anti-recurrence treatment (metaphylaxis) of urolithiasis.
