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The clearance of urea during the dialysis session can be expressed in either or . Time or t {\displaystyle t\,} is the duration of the dialysis session, measured either in minutes or hours.
K (clearance) multiplied by t (time) is a volume (since mL/min × min = mL, or L/h × h = L), and (K × t) can be thought of as the mL or L of fluid (blood in this case) cleared of urea (or any other solute) during the course of a single treatment.
Urea is not associated with toxicity. [4] Standardized Kt/V only models the clearance of urea and thus implicitly assumes the clearance of urea is comparable to other toxins. It ignores molecules that (relative to urea) have diffusion-limited transport - so called middle molecules.
Usually, clearance is measured in L/h or mL/min. [2] Excretion, on the other hand, is a measurement of the amount of a substance removed from the body per unit time (e.g., mg/min, μg/min, etc.). While clearance and excretion of a substance are related, they are not the same thing.
The normal clearance of urea is approximately 100 ml/min. A patient getting a conventional hemodialysis treatment, without remaining residual function, has a urea clearance of 10-15 ml/min. [citation needed]
Urea is usually excreted as a waste product from the kidneys. However, when plasma blood volume is low and ADH is released the aquaporins that are opened are also permeable to urea. This allows urea to leave the collecting duct into the medulla, creating a hyperosmotic solution that "attracts" water.
Renal urea handling is the part of renal physiology that deals with the reabsorption and secretion of urea.Movement of large amounts of urea across cell membranes is made possible by urea transporter proteins.
Fractional excretion of other substances can be measured to determine kidney clearance including urea, uric acid, and lithium. These can be used in patients undergoing diuretic therapy, since diuretics induce a natriuresis. Thus, the urinary sodium concentration and FE Na may be higher in patients receiving diuretics in spite of prerenal ...