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Practical use of urinary fractional excretion

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Abstract

In summary, the FE of electrolytes and minerals is a practical, inexpensive and useful diagnostic tool that may enable recognition of renal and metabofic problems before they progress to an extreme, severely debilitating degree. Published normal values vary widely, but several studies have demonstrated the clinical relevance of FE measurement in renal tubular disease, metabolic diseases (such as NSH and low total body K), exercise-induced rhabdomyolysis, and in the determination of Ca and P balance in horses and ponies. The method is also valid in neonatal foals.
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... Nielsen et al. (1998) observed a calcium urinary concentration of 2.6 g/day from horses fed a diet containing 0.33% calcium. According to King (1994) the maintenance systems that regulate the calcium and magnesium concentrations in the blood work together for the excretion, maintenance and absorption of these electrolytes. Whereas the urine concentration of calcium and magnesium showed no effect of electrolytes supplementation. ...
... The urinary system is extremely efficient in the excretion of chloride, as in the excretion of sodium. According to King (1994) chloride is the urinary anion that is excreted the most, concomitant with sodium and potassium, the two cations excreted in the largest quantities. Nielsen et al. (1998) observed a urinary magnesium excretion of 2.9 g/day in horses fed diets with 0.17% magnesium. ...
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This study was designed to evaluate changes on variables in blood, urine and water balance in horses in response to a single dose of electrolyte supplementation. The essay was conducted on a randomised 3×3 Latin Square design repeated over time, with three animals and three treatments: Treatment 1: control group (without supplementation); Treatment 2: supplementation with a medium dose of electrolytes composed of: 0.25 g of NaCl + 0.125 g of KCl + 0.05 g of CaCl + 0.025 g of MgCl per kg of BW; Treatment 3: supplementation with a high dose of electrolytes composed of: 0.625 g of NaCl + 0.3125 g of KCl + 0.125 g of CaCl + 0.0625 g of MgCl per kg of BW, equivalent to 2.5 times the medium dose of supplementation. The electrolytes were supplied through a nasogastric tube 4 h after the morning meal. The diet provided had a forage:concentrate ratio of 70:30, composed of coastcross hay and commercial concentrate, with an estimated consumption of 2% of body weigth (BW). Horses received 116 mg/kg of BW of commercial mineral salt mixed in the concentrate. Samples of blood, urine and digesta were collected over a 12 h period after supplementation for analysis of sodium, potassium, chloride, calcium and magnesium concentration. Water intake and urine output were also measured. Electrolytic supplementation enhanced (P<0.05) the water intake, water retention and urine output. Blood variables were not altered by electrolyte supplementation (P≯0.05). The supplementation also influenced the sodium and chloride excretion in urine (P<0.05). Urine physicochemical characteristics and the concentration of electrolytes excreted with time were significantly altered as a function of the electrolytes supplementation.
... Factors such as water intake and renal blood flow can interfere with this rate, thereby influencing the excretion of minerals. In addition, calculating the fractional excretion (FE) of the elements can verify their resorption and excretion, which also considers the urinary creatinine level (KING, 1994;FERREIRA et al., 2018). Thus, the aim of this work was to study the renal profile of lambs subjected to two diets with different levels of phosphorus, through urinalysis findings and serum urea and creatinine readings, as well as to determine the urinary FE of Ca, P, and Mg. ...
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Obstructive urolithiasis is common in confined sheep, and a predominant factor predisposing animals to this condition is nutritional management. The objective of this study was to evaluate the effect of different concentrations of phosphorus (P) on urinalysis, serum urea and creatinine, and serum and urine concentrations of calcium (Ca), P, and magnesium (Mg), as well as to establish the fractional excretion (FE) of these elements in confined lambs. Thirty male Santa Inês x Ile de France sheep at four months of age were divided into two groups according to the diet: Group 1 (G1, n = 15), with 0.43% P in their feed; and Group 2 (G2, n = 15) with 0.65% P. The diets consisting of 10% Coast-cross hay and 90% of a concentrate of soybean meal, wheat, and crushed corn were provided for 90 consecutive days, with water ad libitum. The time points (M) of blood and urine collection were determined as M0, immediately before the beginning of the diet, and at 15-day intervals: M1, M2, M3, M4, M5, and M6. Phosphorous-rich diets favored the appearance of triple phosphate crystals in both groups, causing calculogenesis in more than one third of the animals (11/30), emphasizing the relevance of conducting laboratory tests to aid in urolithiasis diagnosis. In addition, FE revealed an increased renal excretion of excess minerals in the diet, and therefore a greater predisposition for stone formation in relation to nutritional management.
... The measurement of urinary ion concentrations of Ca, P, and Mg can provide data regarding the mineral balance by quantifying the excretion of these elements. However, the simple measurement of the concentration of urinary electrolytes cannot be interpreted correctly without considering the urinary volume produced (16) . For this, the values of electrolytes in serum and urine, in addition to serum and urinary creatinine, must be obtained for the calculation of fractional excretion (FE) because the variation in water absorption and excretion hinders interpretation caused by the significant diversity in the concentration of solutes in the urine (17) . ...
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Obstructive urolithiasis is highly prevalent disease in feedlot sheep. Urinary acidification is effective for disease prevention. Forty-five healthy 3-4 month-old male Santa Inês crossbred feedlot lambs were distributed into three groups of 15 animals each. Ammonium chloride (GA) at 400 mg/kg/day/animal, vitamin C (GC) at 4 mg/kg/day/animal, and a combination of the two (GAC) were administered orally for 21 d. Blood and urine samples were taken 7 d before beginning treatment (M0), immediately before (M1), and weekly for 21 d (M2, M3, and M4) for renal function tests, levels of Ca, P, and Mg in serum and urine, urinalysis, and fractional excretion (FE) analysis in these minerals. In groups GA and GAC, pH decreased in M2 and remained acidic throughout the experiment. A significant decrease in serum P and a urinary increase in Ca and Mg occurred in GA. The FE of Ca increased during treatments, but there was no interference with Mg. The FE of P was significantly lower in GA. Ammonium chloride was an effective urinary acidifier in sheep, but vitamin C administered orally did not provide stable results. Thus, based on our results, vitamin C supplementation may not effective for urinary acidification to prevent obstructive urolithiasis.
... A mensuração das concentrações de íons urinários (Ca, P, Na, K, Cl) pode fornecer dados ao balanço mineral por meio de quantificação da excreção desses elementos. Contudo, a simples dosagem da concentração dos eletrólitos urinários não pode ser corretamente interpretada, sem que o volume urinário produzido seja considerado (King 1994). Para isto os valores dos eletrólitos no soro e na urina, além da creatinina sérica e urinária devem ser obtidos para a realização do cálculo da excreção fracionada, devido às variações na absorção e excreção de água, que dificultam a interpretação pela grande diversidade na concentração de solutos na urina (Caple et al. 1982). ...
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... A necessidade do conhecimento do volume urinário produzido não torna tal avaliação um método prático. Porém o volume urinário é diretamente proporcional à taxa de filtração glomerular, que pode ser estimada por meio do uso de uma substância que seja totalmente filtrada e não seja secretada ou absorvida pelos rins (King, 1994). Neiger & Hagemoser (1985) demonstraram que em bovinos, assim como em eqüinos, existe grande correlação entre a creatinina urinária e a densidade específica da urina, indicando, assim, que a creatinina é quase totalmente filtrada passivamente pelos glomérulos, e que são insignificantes as quantidades secretadas ou reabsorvidas pelos túbulos renais, fator importante para utilização dessa substância no cálculo da excreção fracionada em bovinos. ...
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The assessment of calcium and phosphorus nutrition is difficult when using serum concentrations of these elements, because they remain within normal ranges despite a wide variation in Ca and P contents in different diets due to the high efficiency of body homeostasis process. Significant alterations are observed in chronic deficiencies when economic losses have a relevant importance. The use of fractional excretion of Ca and P allow quantitative evaluation without need of timed urine volumetric determinations. Fractional excretion ratios for Ca and P were determined using eight consecutive 45-day urine and serum sample collections performed on 22 heifers before (two samplings) and during pregnancy (six samplings). The values presented by fractional excretion of Ca and P ranged from 1.06% to 3.72% and 1.09% to 2.70%, respectively. There was a tendency to diminishing fractional excretion median values of Ca when comparing before pregnancy with values observed during pregnancy. This experiment showed that there is wide variation in Ca and P fractional excretion in different animals at the same moment and this results in difficulties to access nutritional status of these elements in cattle raised on pasture using this method.
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