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Memorias del Instituto de Investigaciones en Ciencias de la Salud

versão On-line ISSN 1812-9528

Mem. Inst. Investig. Cienc. Salud vol.16 no.2 Asunción ago. 2018 


Nephrolithiasis in Paraguay: Laboratory tools in the identification of etiology and follow-up of the lithiasic patient

Rosa María Guillén Fretes1 

1Universidad Nacional de Asunción, Instituto de Investigaciones en Ciencias de la Salud. IICS-UNA

Nephrolithiasis is a disease characterized by the formation, aggregation and retention of crystals in the urinary tract. Its etiology is complex since it can be the result of the interaction of multiple endogenous, metabolic and environmental factors. The high rate of recurrence of stone formation can exceed 40% in a period of 5 years after the first episode and it can lead to serious consequences for kidney function with its impact on the life quality of the patient1,2.

The evaluation of the lithiasic patient requires several stages, including clinical evaluation, imaging studies, specific laboratory studies, which together allow the identification of the origin of the pathology. The precise identification of the causes that originated the formation of the urinary stone is essential for the selection of appropriate and specific therapeutic measures for each patient1.

The clinical laboratory provides relevant information in etiological research allowing the analysis of the composition of the stone and the concentrations of crystallization promoter and inhibitors compounds known as metabolic profile, in addition to the integrated analysis of these concentrations through the use of specific software that allow the identification of urinary saturation rates at a specific time. In the follow-upof the patient through serial studies of crystalluria, carried out according to international protocols with a frequency of at least three per year, allows the early evaluation the efficacy of therapeutic measures3-5.

The analysis of the kidney stone using combined physical methods and the morphological classification described by Daudon et al. has been implemented in the country since 20076.This type of methodology has multiple advantages with respect to conventional chemical analysis, which includes sufficient sensitivity for trace element detection, the study of the stone per stratum identifying the chronology of formation, the ability to detect crystalline forms even in complex mixtures, and identifying compounds such as xanthine, and other drugs. These characteristics allow the recognition of etiological factors during the formation of the stones. Several studies indicate that in accordance with Western countries the oxalocalcic lithiasis is the most frequent in Paraguay. On the other hand, infectious factors, that trigger carbapatite and struvite stones, are added to those voluminous stones that require invasive urological interventions for their removal7-10.

The metabolic evaluation is useful for the detection of high concentrations of crystallization promoters or the deficit of crystallization inhibitors present at the time of analysis11.The analytes included can vary widely according to the protocols used. Several articles with national data show strikingly hypocitraturia as one of the most frequent factors in both adults and children, followed by hypercalciuria, as well as an insufficient diuresis volume that leads to a phenomenon of concentration which is also a remarkable fact12-14. The interpretation of these values individually is a complex process. The incorporation of computer tools for the integrated analysis of metabolic profile data and the generation of true crystallization risk indexes is an important advance. These tools have been used in the country both for a pre-treatment base evaluation, as well as in the post-treatment phase, showing significant differences in the diuresis volume of the post-treatment patients, as well as a significant decrease in the risk of uric acid crystallization after 6 months of follow-up15.

The use of crystalluria as a marker of the crystallization risk and follow-up tool of the lithiasic patient is recommended internationally due to the simplicity of the technique and its usefulness to predict relapse risks5.This marker has been used usually in the follow-up of pediatric lithiasic patients, with a marked decrease in the presence of crystals in the treatment phase, showing the efficacy of the therapeutic measures. On the other hand, it has proved been crucial in the follow-up of a case of genetic lithiasis by cystinuria using the global crystalline volume parameter and has allowed the precise identification of crystals with unusual morphology and that were associated with drugs, more specifically antibiotics16-18.

The incorporation of specialized biochemichal techniques in the area of renal lithiasis makes possible, for those patients affected by this pathology, to have access to the necessary tools for the choice of specific therapeutic measures and therefore reduce the risk of recurrence in a tangible way with the improvement in the quality of life conditions. However, despite the effort made so far, it is important to emphasize that this kind of enterprise requires greater public investments that allow access to a greater number of patients to this diagnostic possibility.


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12. Guillén, R, Ruíz, I, Stanley, J, Ramírez, A, Pistilli, N. Evaluación de parámetros litogénicos con urolitiasis que concurrieron al Instituto de Investigaciones en Ciencias de la Salud en el año 2009. Mem Inst Investig Cienc Salud. 2010;8(1):14-21. [ Links ]

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15. Guillén R, Ramos C, Ayala R, Funes P, Ruiz I, Zenteno J, et al. [Lithogenic risk index in urinary lithiasis patients and their evolution after treatment.]. Arch Esp Urol. 2017 Oct;70(8):725-31. [ Links ]

16. Funes PRI, Rivas L, Zenteno J, Granado D, Echague G, Guillén R. Cristaluria en niños litiásicos que concurrieron al IICS-2011-2013. Pediatr Asunción. 2016;43(2):123-8. [ Links ]

17. Guillén R, Funes P, Ruiz I, Duarte C, Mereles B. Litiasis por cistina: Reporte de un caso. Mem Inst Investig Cienc Salud. 2014;12(1):51-6 [ Links ]

18. Guillén R, Franco L, Sánchez G, Ortíz V, Herebia L, Ruiz I, et al. Cristalurias medicamentosas en el laboratorio de urgencias: Reporte de dos casos. Mem Inst Investig Cienc Salud. 2016;14(2):106-9. [ Links ]

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