Nephrolithiasis (KSD) is currently an important medical and social problem. KSD is a disease associated with metabolic disorders in the body, in which stones are formed in the kidneys and urinary tract. The prevalence of Nephrolithiasis (KSD) can reach 20%, depending on the region. The most common kidney stones are calcium-containing ones: calcium oxalate (CaOx), calcium phosphate (CaP) and mixed (CaOx and CaP). The frequency of their detection, according to various authors, reaches 60–80% and, according to the results of modern epidemiological studies, in recent decades there has been an increase in their occurrence in the general population. On the contrary, the number of phosphate "infectious" stones tends to decrease. The incidence of uric acid stones remains quite high, amounting to 2–15%, reaching 50–75% in endemic regions. Most experts explain the increase in the incidence of KSD not so much by the versatility of genetically predisposing factors leading to a violation of metabolic processes in the human body, but by the influence of multiple environmental factors. The latter include climatic features; food dietary preferences and drinking regime; professional features associated not only with work in hot industries, but also with a decrease in the level of physical activity; an increase in life expectancy associated with an increase in the incidence of diabetes mellitus, metabolic syndrome, hormonal disorders causing various metabolic disorders, accompanied by metabolic disorders of stone-forming substances. The features of the course of uric acid nephrolithiasis include a pronounced tendency to recurrent stone formation, especially in the absence of constant metaphylactic measures. On the other hand, uric acid stones are the only type of kidney stones that can be effectively dissolved and for which effective metaphylaxis is possible. Understanding the etiopathogenetic processes, which results in the formation of uric acid stones, is of paramount importance in order to select an effective method of treatment and prevention of stone re-formation. The main factors in the development of uric acid nephrolithiasis include a failure of the purine bases exchange, leading to the formation and/or excretion of an increased amount of uric acid, and a persistently low urine pH level associated with a small volume of excreted urine. Elevated serum uric acid levels are a common clinical finding. Hyperuricemia is more common among blacks and men, and uric acid levels in men are fairly stable throughout life. The relatively low level of uricemia in women of reproductive age is due to the effect of estrogens on the tubular excretion of uric acid. With the onset of menopause, the level of uric acid rises and approaches that of men of the corresponding age. Low uric acid levels are also observed in children, and they begin to rise during puberty, reaching the values in adults. Disorders of purine metabolism in most cases are genetically predisposed or determined. Hyperuricemia or a predisposition to it is transmitted from fathers through healthy mothers and grandmothers or grandfathers (great-grandfathers) on the maternal side.

Three main sources of uric acid formation in the human body have been identified: from purines released during tissue breakdown, from synthetically formed purines, and from purines supplied with food. The alimentary factor provides one third of the total amount of purines, and their additional intake as a result of increased consumption of protein-containing products of both animal and plant origin can disrupt a very rigid balance of uric acid in the body. Obesity, impaired insulin resistance, gout, neoplastic processes and genetically determined hyperuricemia are an additional factor in the formation of stones from uric acid.

Thus, the leading factors in uric acid stone formation include the saturation of urine with uric acid and its salts as a result of excessive intake or production of uric acid, low urine output and a stable acidic urine reaction. Numerous clinical studies have shown that stones consisting of uric acid, uric acid dihydrate and mixed stones consisting of uric acid and 25% calcium oxalate are subject to effective litholysis. Based on the foregoing, a prerequisite for the appointment of litholytic therapy and effective metaphylaxis is considered to be knowledge of the chemical composition of the stone and the results of a full examination in order to identify metabolic disorders and concomitant diseases. The basis for the dissolution of uric acid stones is the alkalization of urine to values ​​at which uric acid from the insoluble lactam/keto form goes into the soluble lactam/enoform. Currently, the recommended target pH values ​​of urine for dissolution of uric acid stones are 7.0–7.2, to prevent the formation of relapses, it is shown to maintain the pH in the range of 6.2–6.8. Litholytic therapy is carried out with citrate mixtures. The dosage of the citrate mixture is selected individually. Any measures aimed at dissolving or preventing the recurrence of uric acid stones must begin with an explanation of the conditions for stone formation and measures to prevent them. The main recommendation for reducing urine satiety is to increase the volume of fluid consumed until the daily urine output is at least 2.0–2.5 liters. Any disease is easier to prevent than to cure. It is necessary to engage in the prevention of KSD - the prevention of the onset of the disease from childhood.

Source: Saenko V.S., Pesegov S.V., Frolova E.A. The role of drinking and dietary factors in effective litholysis and metaphylaxis of uric acid nephrolithiasis. Urology. 2019; 2: 121-126. Doi: https: //dx.doi.org/10.18565/urology.2019.2.121-126