Comparación de los parámetros de cristalización urinaria entre pacientes asmáticos y pacientes sanos

Abstract

Introduction: although urinary lithiasis is a rare entity in the pediatric age, its incidence is increasing rapidly over the last decades. Apart from changes in lifestyle and diet of the population, other factors would be responsible for this, such as the increased prevalence of diseases that predispose to its appearance. Recently a study has found a possible association between asthma and lithiasic disease, whose association had not been previously described and whose link is unknown. Objective: the main objective is to determine whether there are differences in the urinary composition of asthmatic children with respect to that of healthy children, either in the levels of excretion of lithiasis modulators or in the values of urinary oversaturation. The secondary objectives are to determine 12h urine reference values for the parameters analysed, to investigate the possible influence of diet and drug use on urine composition and to investigate the possibility of eliminating the effect of diuresis fluctuation on urine oversaturation values by using a standardisation procedure. Methods: cross-sectional observational study in which different urinary parameters were compared between a cohort of healthy patients and a cohort of asthmatic patients, defined as such based on the criteria of the Global International Network for Asthma. The participants collected all the urine emitted over a 12-hour period including night rest and provided it for analysis. The samples were determined for urine volume, pH and concentration of sodium, potassium, chlorine, calcium, phosphorus, magnesium, oxalate, citrate, uric acid and urea. From these data, the total excretion of these solutes was calculated and normalized according to the patient's body surface, and the oversaturation values of several urinary salts of the families of calcium oxalates, calcium phosphates and urates were estimated using the JESS Urine Expert software. Multiple comparisons were made depending on the group the pati ent belonged to and also on the medication they received. Results: The sample comprised the urine collection of 45 asthmatic patients and 44 healthy patients with similar characteristics. Urine from the asthmatic group did not present statistically significant differences with respect to that of healthy patients neither in the levels of lithiasis modulators nor in the calculated levels of oversaturation. The following associations between urinary parameters and medication were found: citraturia was correlated with the dose of steroids (?std = 0.496, p = 0.05) and with the use of ?2 long-acting agonists (?std = -0.487, p = 0.001). Natriuria correlated with the use of ?2 long-acting agonists (?std = 0.424, p = 0.001) and with the use of montelukast (?std = -0.585, p = 0.028). The use of LABA correlated with uric acid excretion, although statistical significance was not reached (?std = -0.361, p = 0.053). The "urinary parameters estimating dietary characteristics" show similar correlations to those previously described with the foods they represent. Depending on the parameter studied, the diet would explain between 9.1 and 44% of its variability. Depending on the oversaturation value studied, diuresis explains between 22.3 and 42.6% of its variability. Discussion: the parameters of urinary crystallization of asthmatic children are similar to those of healthy children. The medication used for asthma control could influence the urinary composition, although its incidence on the lithogenic risk would be little relevant. The characteristics of the patients' diet, estimated through different urinary parameters, seems to have a high impact on the urinary composition of the participants. Diuresis has a considerable influence on the levels of oversaturation, which makes comparison between patients difficult. Standardization of oversaturation could be a tool to help eliminate this problem, although more studies are needed to properly delimit its usefulness.