Browsing by MeSH term "Calcium Oxalate"
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Publication Can Randall's plug composed of calcium oxalate form via the free particle mechanism?(BioMed Central (BMC), 2017-09-08) Grases, F; Sohnel, OBackground: The likelihood of a Randall's plug composed of calcium oxalate monohydrate (COM) forming by the free particle mechanism in a model of kidney with a structure recently described by Robertson was examined at the most favourable conditions for the considered mechanism. Methods: The Robertson model of the kidney is used in the following development. The classical theory of crystallization was used for calculations. Results: Initial COM nuclei were assumed to form at the beginning of the ascending loop of Henle where the supersaturation with respect to COM has been shown to reach the threshold level for spontaneous nucleation. Nucleation proceeds by a heterogeneous mechanism. The formed particles are transported in the nephron by a laminar flow of liquid with a parabolic velocity profile. Particles travel with a velocity dependent on their position in the cross-section of the nephron assumed to be straight tubule with smooth walls and without any sharp bends and kinks. These particles move faster with time as they grow as a result of being surrounded by the supersaturated liquid. Individual COM particles (crystals) can reach maximum diameter of 5.2 x 10(-6) m, i.e. 5.2 mu m, at the opening of the CD and would thus always be washed out of the CD into the calyx regardless of the orientation of the CD. Agglomeration of COM crystals forms a wractal object with an apparent density lower than the density of solid COM. The agglomerate that can block the beginning of the CD is composed of more crystals than are available even during crystaluria. Moreover the settling velocity of agglomerate blocking the opening of the CD is lower than the liquid flow and thus such agglomerate would be washed out even from upward-draining CD. Conclusions: The free particle mechanismmay be responsible for the formation of a Randall's plug composed by COM only in specific infrequent cases such as an abnormal structure of kidney. Majority of incidences of Randall's plug development by COM are caused by mechanism different from the free particle mechanism.Publication Effect of sample time on urinary lithogenic risk indexes in healthy and stone-forming adults and children(BioMed Central (BMC), 2018-12-19) Rodríguez, Adrián; Saez-Torres, Concepcion; Mir Perelló, Maria Concepción; Casasayas-Carles, Paula; Rodriguez-Garcia, Nuria; Rodrigo, Dolores; Frontera-Juan, Guillem; Buades-Fuster, Juan Manuel; Gómez Cobo, Cristina; Costa-Bauza, Antonia; Grases, FelixBackground: The diagnosis and follow-up of stone forming patients is usually performed by analysis of 24-h urine samples. However, crystallization risk varies throughout the day, being higher at night. The main objective of this study is to evaluate the urinary crystallization risk in adults and children by calculating risk indexes based on different collection periods. Methods: The study included 149 adults (82 healthy and 67 stone-formers) and 108 children (87 healthy and 21 stone-formers). 24-h urine was collected, divided into 12-hdaytime sample (8am to 8pm), and 12-h overnight sample (8pm to 8am next morning). Solute concentrations, the calcium to citrate ratio (Ca/Cit), and the ion activity product of calcium oxalate (AP[CaOx]) and calcium phosphate (AP[CaP]) were calculated in each 12-h sample and in overall 24-h urine. Assessments were also related to stone type.ResultsCa/Cit and AP(CaOx) were significantly higher in stone forming patients than in healthy subjects. The 12-h overnight samples had the highest values for both risk indexes, confirming a greater risk for crystallization at night. The AP(CaP) index was significantly higher in patients with pure hydroxyapatite stones than healthy controls, but was not significantly different between stone-formers overall and healthy controls. Conclusions: The calculation of risk indexes is a simple method that clinicians can use to estimate crystallization risk. For this purpose, the use of 12-h overnight urine may be a reliable alternative to 24-h collections.Publication Fructose increases risk for kidney stones: potential role in metabolic syndrome and heat stress(BioMed Central (BMC), 2018-11-08) Johnson, Richard J; Perez-Pozo, Santos E; Lillo, Julian Lopez; Grases, Felix; Schold, Jesse D; Kuwabara, Masanari; Sato, Yuka; Hernando, Ana Andres; Garcia, Gabriela; Jensen, Thomas; Rivard, Christopher; Sanchez-Lozada, Laura G; Roncal, Carlos; Lanaspa, Miguel ABackground: Fructose intake, mainly as table sugar or high fructose corn syrup, has increased in recent decades and is associated with increased risk for kidney stones. We hypothesized that fructose intake alters serum and urinary components involved in stone formation. Methods: We analyzed a previously published randomized controlled study that included 33 healthy male adults (40-65years of age) who ingested 200g of fructose (supplied in a 2-L volume of 10% fructose in water) daily for 2 weeks. Participants were evaluated at the Unit of Nephrology of the Mateo Orfila Hospital in Menorca. Changes in serum levels of magnesium, calcium, uric acid, phosphorus, vitamin D, and intact PTH levels were evaluated. Urine magnesium, calcium, uric acid, phosphorus, citrate, oxalate, sodium, potassium, as well as urinary pH, were measured.ResultsIngestion of fructose was associated with an increased serum level of uric acid (p<0.001), a decrease in serum ionized calcium (p=0.003) with a mild increase in PTH (p<0.05) and a drop in urinary pH (p=0.02), an increase in urine oxalate (p=0.016) and decrease in urinary magnesium (p=0.003). Conclusions: Fructose appears to increase urinary stone formation in part via effects on urate metabolism and urinary pH, and also via effects on oxalate. Fructose may be a contributing factor for the development of kidney stones in subjects with metabolic syndrome and those suffering from heat stress.Trial registrationClinicalTrials.gov NCT00639756 March 20, 2008.