Although the correct name in the Canadian unit of measure is urea, you may still hear people use the term B. An elevated urea and creatinine indicates the kidneys are not working called renal failure. Although urea is filtered into the urine by the kidney, some of the filtered urea will get reabsorbed and reused by the body.
Consequently, urea levels in the bloodstream can rise if the kidney fails, if the patient is making a lot of new protein anabolic or breaking a lot of protein down catabolic or if the patient is dehydrated.
Creatinine is a byproduct of muscle protein metabolism. Virtually all of the creatinine that we make is filtered by the kidney and eliminated in the urine. Creatinine is a more specific test of kidney function.
Chronic kidney disease CKD is defined by reduction in GFR, which in turn is associated with increased plasma creatinine and urea concentrations. The causes of AKI are categorized under three headings: prerenal reduced renal perfusion, often because of hypovolemia , intrinsic renal damage to the kidney itself — glomerular or tubular , postrenal obstruction of urine flow [18]. Prerenal causes hypovolemia due to severe vomiting, blood loss, osmotic diuresis, etc.
Whatever the precise cause, prerenal AKI exists despite a presumed normally functioning kidney. Part of the response to the hemodynamic instability that underlies prerenal AKI is increased renal reabsorption of urea [19] and this contributes to the rising plasma urea consequent on reduced GFR.
These studies suggest that a high BCR can be associated with poor prognosis and therefore not necessarily indicative of just prerenal AKI. Credence for this view is provided by the observation that for critically ill patients with normal serum creatinine, plasma urea concentration is independently associated with mortality [23]. Heart and kidney function are closely related in health and disease.
Pathologically this link is manifest as the cardiorenal syndrome [24]. These patients require immediate transfer to intensive care for optimal care and best chance of survival.
A recent confirmatory study validated this clinical application of urea measurement [31]. The authors of this study retrieved plasma BUN urea results at admission and 24 hours later from patients with acute pancreatitis. Preand postdialysis plasma urea concentrations are used to calculate the urea reduction ratio URR thus:.
Urea measurement does, however, have some clinical value, especially when measured in tandem with plasma creatinine. Measurement of urea alone has proven value in assessment of patients with acute pancreatitis and monitoring effectiveness of hemodialysis.
May contain information that is not supported by performance and intended use claims of Radiometer's products. See also Legal info. Radiometer and acutecaretesting. Printed from acutecaretesting. October Urea and creatinine concentration, the urea:creatinine ratio. Summary This second of two articles on understanding the clinical value of measuring urea concentration explores the clinical value of simultaneous measurement of urea and creatinine and calculating the urea:creatinine ratio. For the blood concentration of an endogenously produced substance to most accurately reflect GFR in health and disease, that substance must have the following properties: It must be excreted only by the kidneys It must be freely filtered from blood at the glomerulus It must be neither reabsorbed from the filtrate to blood nor secreted from blood to the filtrate by renal tubulecells i.
For example: Patient A has: plasma urea 5. Freely filtered at glomerulus Yes Yes Not reabsorbed or secreted by renal tubule cells A variable quantity of urea reabsorbed from filtrate, dependent on state of hydration, renal blood flow, etc. Creatinine is not reabsorbed.
Virtually all filtered creatinine appears in urine. However, a small amount is secreted by proximal tubules. Concentration in blood unaffected by factors other than GFR, i. Plasma levels are ethnically and gender dependent, and are transiently increased by eating cooked meat. Gastrointestinal GI bleed Gastrointestinal bleeding represents a non-renal cause of increased plasma urea. Heart failure Heart and kidney function are closely related in health and disease.
Clinical application of plasma urea measurement alone 1. Clinical application of plasma urea measurement alone 2. Higgins C. Urea and the clinical value measuring blood urea concentration. Baum N et tal. Blood urea nitrogen and serum creatinine. Urology ; 5, 5: Traynor J et tal. How to measure renal function in clinical practice. BMJ Clinical research ed.
McWilliam A et tal. Laboratory tests of renal function. Lyman JL. Blood urea nitrogen and creatinine. Emerg Med Clin North Am ; 4, 2: Jurado R et tal. The decreased serum urea nitrogen-creatinine ratio. Arch Intern Med ; , Snook JA et tal. Value of a simple biochemical ratio in distinguishing upper and lower sites of gastrointestinal haemorrhage. Lancet ; 1, Felber S et tal.
J Pediatr Gestroenterol Nutr ; 7, 5: Olsen LH et tal. Stools containing altered blood-plasma urea: creatinine ratio as a simple test for the source of bleeding. Br J Surg ; 78, 1: Ernst AA et tal. Am J Emerg Med; 17, 1: Grouping factors were in the order in which the subjects were earthed.
Intergroup comparisons earthed versus unearthed were performed. To minimize the familywise probability of a type I error, only between-subject comparisons at the times 0, 15, 30, and 40 minutes were considered. Significantly lower blood urea levels were observed in subjects earthed during exercise and relaxation Table 2. There were significant differences in blood urea levels between subjects earthed in the first week and those unearthed in the second week Figure 3 b and between subjects who were earthed in the second week and those unearthed in the first week Figure 3 c.
These differences were clearer when considering the two groups, the earthed subjects and the unearthed subjects, regardless of the week in which they were earthed Figure 3 a. These significant differences in blood urea levels were observed in both groups at the beginning of exercise , during exercise after 15 minutes and 30 minutes , and after 40 minutes of relaxation. Creatinine concentrations in earthed subjects were not significantly changed in the exercise phase but were significantly lower in the 40th minute of the recovery phase in earthed subjects in the second week Table 3 Figures 4 a , 4 b , and 4 c.
In our experiment, we selected a homogeneous group of young, healthy men with similar aerobic endurance measured by the indicator of maximal oxygen uptake. In all cases, we observed lower blood urea levels in individuals under earthing compared with unearthed subjects from the beginning to the end of the experiment during exertion and recovery.
In our study, we showed the opposite results to Foran et al. All subjects earthed during the exercise phase and in the recovery period had diminished levels of urea. Urea is a waste product of amino acid catabolism. Consequently, its plasma concentration is directly related to the amount of protein in the diet [ 9 ].
Our study showed that the observed alterations in blood urea levels were not dependent on a high or low protein diet. Urea is excreted by the kidneys. Urea is filtered by the glomerular capillaries, and it enters the renal tubule. Approximately half of urea is reabsorbed passively by diffusion, but the remainder is excreted in the urine. Lower blood urea levels suggest increased glomerular filtration and excretion in the urine or diminished reabsorption in the tubules.
All these processes may result from changes in the electrical, aqueous environment in humans who are earthed. Urea is passively reabsorbed in the renal tubules. The rate of transport is determined by the electrochemical gradient for diffusion of the substance across the membrane and the permeability of the membrane for the substance. Additionally, glomerular filtration depends on the negative charge of the basement membrane of podocytes, which restrict large negatively charged molecules [ 10 , 11 ].
Changes in the electrical potential of the membrane of tubular and glomerular cells can affect filtration and absorption. Another waste product of metabolism is creatinine, which is a larger molecule than urea, and is impearmeant to the tubular membrane.
Therefore, almost all of the creatinine filtered by the glomerulus is excreted in the urine [ 10 , 11 ]. In our study, in contrast to the changes in urea, we did not observe altered levels of creatinine in the exercise phase. Lower creatinine concentrations at the end of the recovery phase in earthed subjects may have resulted from increased kidney filtration. Urea formation occurs in the liver as a result of the process of deamination of amino acids and use of ammonia [ 12 ].
The activity of enzymes participating in the urea cycle is dependent on hydrogen ion concentrations, which can be affected by alterations in the distribution of charges in the aqueous environment during earthing.
At a low pH, urea synthesis is decreased and consumption is reduced. We consider that lower levels of urea in training subjects under earthing may be caused by decreased urea formation in the urea cycle.
Therefore, earthing may inhibit hepatic catabolism of proteins during exercise. Excessive breakdown of proteins is observed in individuals during space flight and inactivity [ 10 , 11 ]. In this aspect, earthing can have the opposite effect on metabolism of proteins.
Resistance exercise increases muscle protein synthesis [ 10 , 11 ]. Rates of muscle protein synthesis and degradation during exercise and in recovery are affected by the type of exercise, age, and state of nutrition. Exercise depresses muscle protein synthesis, whereas muscle protein breakdown probably remains unchanged during exercise. After exercise in the fasted state, synthesis and breakdown of proteins are elevated, when the net muscle protein balance remains negative [ 14 ]. A single bout of resistance-type exercise accelerates muscle protein synthesis rates.
An increased rate of protein synthesis persists hours after exercise [ 15 , 16 ]. Resistance exercise under earthing may multiply this effect. Direct contact with the earth or with a wire during exercise decreases blood urea nitrogen levels, which could result from the inhibition of breakdown of proteins in various tissues. However, there is no convincing evidence for reduced proteolysis of contractile proteins in active muscle in this study. At the end of the recovery phase, significantly lower creatinine levels suggest decreased breakdown of muscle creatine.
A positive protein balance could be the result of earthing during exercise. Contact with the earth may have an important effect on human health in rest and exercise [ 17 ], especially for training athletes. Their goal is to maintain or increase lean body mass. An increase in muscle size and thus mass is caused by an increase in protein synthesis. Increased protein synthesis is reflected by a positive nitrogen balance.
Earthing during exercise prevents protein degradation and thus helps to sustain a positive nitrogen balance. Our study shows that blood urea concentrations are lower in subjects who are earthed connected to the earth potential with the use of copper wire during physical exercise and recovery compared with the same subjects who are not earthed during the same period of exercise and recovery.
These results suggest that earthing during exercise inhibits hepatic protein catabolism or increases renal urea excretion. Earthing during exercise affects protein metabolism, resulting in a positive nitrogen balance. This phenomenon has fundamental importance in understanding human metabolic processes and may have implications in training programs for athletes.
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