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Creatinine clearance exceeds GFR due to creatinine secretion, [4] which can be blocked by cimetidine. Both GFR and C Cr may be accurately calculated by comparative measurements of substances in the blood and urine, or estimated by formulas using just a blood test result ( eGFR and eC Cr ) The results of these tests are used to assess the ...
The glomerular filtration rate is the flow rate of filtered fluid through the kidney. The creatinine clearance rate (C Cr or CrCl) is the volume of blood plasma that is cleared of creatinine per unit time and is a useful measure for approximating the GFR. Creatinine clearance exceeds GFR due to creatinine secretion, [1] which can be blocked by ...
The renal clearance ratio or fractional excretion is a relative measure of the speed at which a constituent of urine passes through the kidneys. [ 1 ] [ 2 ] It is defined by following equation: c l e a r a n c e r a t i o o f X = C x C i n {\displaystyle clearance\ ratio\ of\ X={\frac {C_{x}}{C_{in}}}}
Effective renal plasma flow (eRPF) is a measure used in renal physiology [1] to calculate renal plasma flow (RPF) and hence estimate renal function.. Because the extraction ratio of PAH is high, it has become commonplace to estimate the RPF by dividing the amount of PAH in the urine by the plasma PAH level, ignoring the level in renal venous blood.
Para-aminohippurate (PAH) clearance is a method used in renal physiology to measure renal plasma flow, which is a measure of renal function. [citation needed]PAH is completely removed from blood that passes through the kidneys (PAH undergoes both glomerular filtration and tubular secretion), and therefore the rate at which the kidneys can clear PAH from the blood reflects total renal plasma flow.
Therefore, creatinine concentrations in blood and urine may be used to calculate the creatinine clearance (CrCl), which correlates approximately with the glomerular filtration rate (GFR). Blood creatinine concentrations may also be used alone to calculate the estimated GFR (eGFR). The GFR is clinically important as a measurement of kidney function.
where C is the concentration [mol/m 3]; t is the time [s]; K is the clearance [m 3 /s]; V is the volume of distribution [m 3]; From the above definitions it follows that is the first derivative of concentration with respect to time, i.e. the change in concentration with time.
It is complex and tedious to calculate, although web-based calculators are available to do this fairly easily. Many nephrologists have difficulty understanding it. 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.