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Kt/V, like the URR, focuses on urea as the target solute, and is based on the assumption that removal of urea is from a single space – urea distribution volume, or similar in capacity to the total body water. The urea distribution volume , although traditionally thought of as 60% of body weight, may actually be closer to 50% of the body ...
So the ratio of K × t / V is a so-called "dimensionless ratio" and can be thought of as a multiple of the volume of plasma cleared of urea divided by the distribution volume of urea. When Kt/V = 1.0, a volume of blood equal to the distribution volume of urea has been completely cleared of urea.
The next line to the right (in light blue) shows the effects of urea generation during a typical 3-4 hour treatment. Urea generation during such a session results in a slightly lower URR (by about 0.10) than expected as a result of urea clearance, due to the fact that urea is being added to the body by generation during the dialysis session.
The major functions of these lining cells are the reabsorption of water and small molecules from the filtrate into the blood, and the secretion of wastes from the blood into the urine. [citation needed] Proper function of the kidney requires that it receives and adequately filters blood.
Kt/V is a ratio of the pre- and post-dialysis urea concentrations. Standardized Kt/V is an equivalent clearance defined by the initial urea concentration (compare equation 8 and equation 10 ). Kt/V is defined as (see article on Kt/V for derivation):
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.
Substance Approximate molecular mass (g/mol) [1] Effective molecular radius [1] conc. in ultrafiltrate / conc. in blood plasma [1]; sodium: 23: 0.1: 1.0 potassium: 39: 0.14: 1.0 chloride: 35.5
The structure of the molecule of urea is O=C(−NH 2) 2.The urea molecule is planar when in a solid crystal because of sp 2 hybridization of the N orbitals. [8] [9] It is non-planar with C 2 symmetry when in the gas phase [10] or in aqueous solution, [9] with C–N–H and H–N–H bond angles that are intermediate between the trigonal planar angle of 120° and the tetrahedral angle of 109.5°.