Introduction. The study of lithogenic substances excretion in stone formers with pure monomineral stones allows us to identify characteristic metabolic changes, the long-term effect of which determines the originality of the pathogenetic mechanism features of the formation of urinary stones consisting of pure minerals. The problem of studying lithogenesis of «pure» (monomineral) stones in stone formers is of great clinical importance, since it assumes the existence of various approaches to prevention and metaphylaxis of urolithiasis in patients with «pure» stones and mixed stones.
Materials and methods. We examined 982 patients with urolithiasis (439 men and 543 women aged from 18 to 79 years. Of these, 837 patients (384 men and 453 women) had «pure» urinary stones of various types, represented by one mineral. Metabolic parameters of excretion in patients were studied men and women with monomineral urinary stones of various chemical types.
Results. In oxalate stones, the most active accumulation of the calcium oxalate mineral component and an increase in the number of «pure» oxalate stones by 1.25 times was observed in men than in women (p=0.046). Increased calcium excretion activates oxalate lithogenesis in men, as opposed to women, contributing to the accumulation of veddelite in pure oxalate stones. In contrast to women, the accumulation of calcium oxalate in stones in men is associated with increased excretion of uric acid, phosphates, and partly magnesium (p<0.01). In uric acid stones consisting of pure uric acid and uric acid dihydrate, pure uric acid stones were 1.52 times more common in women than in men (p<0.01), and did not depend on the level of uricosuria. Patients with pure uric acid stones had lower urine pH than patients with pure calcium-oxalate stones. The accumulation of uric acid in stones to the level of pure uric acid stones was accompanied in the groups of men by an increase in phosphaturia (p=0.021), and in the groups of women – with an increase in body mass index (p=0.028). Men with 100% uric acid stones had higher levels of excretion of calcium, uric acid and phosphates compared to female patients by 1.21 times, 1.3 times and 1.26 times, respectively (p<0.05). Urinary stones from pure carbonate apatite were rare in men and women. In women, stones of mixed composition with 80-90% carbonatapatite were more often detected, and in men with 60-70% of this mineral. In men, compared with women, with the accumulation of carbonatapatite in stones, an increase in the excretion of calcium, uric acid, phosphates and magnesium was observed (p<0.05). About 80% of mixed stones in stone formers men and women are pure calcium oxalate-phosphate bimineral stones consisting only of carbonate apatite and calcium oxalate. In men, in contrast to women, there was a predominance of calcium oxalate (1.24 times), the accumulation of which in these stones was higher. It is associated with increased excretion of calcium, uric acid, phosphates, and magnesium (1.41-fold, 1.32-fold, 1.35-fold, and 1.33-fold, respectively (p<0.05). Men with calcium oxalate-phosphate stones had higher calcium excretion than those with pure calcium oxalate or carbonate apatite stones and lower urine pH values than those with carbonate apatite stones (p<0.01). In women, level of calciuria did not play a big role in the genesis of pure calcium oxalate-phosphate, calcium oxalate and carbonate apatite stones. A more important factor in their lithogenesis was the alkaline reaction of urine, which led to the activation of carbonate apatite stone formation.
Conclusion. The formation of urinary stone and the distribution of its mineral components depend on the interaction of various metabolic factors. The study of groups of patients with pure (100%) monomineral stones and patients with stones of mixed composition, in which main mineral is only the predominant part, allows us to identify characteristic complexes of lithogenic metabolic factors that distinguish these groups of patients from each other. This approach is important both for understanding the pathogenetic mechanisms of stone formation, and for choosing the directions of empirical therapy for urolithiasis and developing further metaphylactic measures that also take into account the gender of patients.
