Creatinine clearance, normal values

Creatinine clearance (Cld) is renal clearance (Cl,) applied to endogenous creatinine. It is used to monitor renal function and is a valuable parameter for calculating dosage regimens in elderly patients or those suffering from renal dysfunction. Normal creatinine clearance (Clc) values are ... 

A middle-aged woman who had taken germanium lactate-citrate for at least a year (with an estimated cumulative dose of 32.1 g of germanium) developed renal insufficiency with a creatinine clearance of 10 ml/minute, raised creatine kinase activity, and moderately raised hver enzymes. Biopsy showed highly vacuolated cytoplasm in the epithelial cells of the distal renal tubules and microvesicular and macrovesicular steatosis of centrilobular hepatocytes. After withdrawal of the germanium the laboratory values normalized but moderately severe renal impairment persisted (SEDA-16, 231). 

Cross-sectional studies demonstrate decreased GFR as a function of age when GFR is measured as inulin, iothalamate, or creatinine clearance. The Baltimore Longitudinal Study on Aging, an evaluation of 254 normal healthy subjects, revealed that creatinine clearance decreases at the rate of approximately 0.75 mL/min per 1.73 m per year beginning at the fourth decade of life. These subjects were evaluated prospectively for up to 23 years. Interestingly, approximately one-third of the subjects showed no change in renal function from their baseline value, and a small number showed an increased clearance. These changes may be due to normal physio-... 

Unbound concentration measurements provide the best means for individualizing phenytoin therapy in patients with renal insufficiency. They are however not widely available nor routinely utilized. Therefore methods have been presented to equate an observed total concentration in patients with ESKD receiving hemodialysis treatment to what would be expected in patients with normal renal function. Liponi and associates suggested a method by which the total phenytoin concentration (Cni ° ) in patients with creatinine clearance values of 10 to 24 mL/min or less than 10 mL/min can be equated to the concentration that would be observed if plasma protein concentrations and phenytoin-binding characteristics were normal. A patient s equated total phenytoin concentration (Ce ° ) would thus equal ... 

A a absorption rate constant k elimination rate constant koD. elimination rate constant during dialysis KF ratio of the patient s creatinine clearance to the assumed normal value of 120 mL/min... 

Only approximate guidelines can be given. See text for explanations and limitations. Clc creatinine clearance ULN, upper limit of normal laboratory values. 

C. The measurement of the phosphate excretion index (Nil). Since the phosphate/creatinine clearance ratio is normally directly related in a known manner to plasma phosphate concentration (MIO), the observed Cp/Ccr in any given case can be compared with the normal mean value at the same plasma concentration. The difference is called the Phosphate Excretion Index (PEI) and its normal range is —0.09 to +0.09. The values in hyperparathyroid cases usually lie above the upper normal limit and in hypoparathyroid cases below the lower limit (Nil) (Fig. 10). 

D. Phosphate reabsorption per 100 ml of glomerular filtrate. If the plasma phosphate concentration is multiplied by the phosphate/creatinine clearance ratio, an approximate figure is obtained for the amoimt of phosphate reabsorbed per 100 ml of glomerular filtrate (T7). The normal range of this value is approximately 2-4mg/100ml filtrate (Nil). 

Serum creatinine concentration is constant unless there is a change in the rate of production of creatinine in the body or creatinine clearance. The creatinine clearance in normal kidneys is approximately 110 to 130 mL/min. This value declines with progressive renal impairment, and it drops to zero with severe renal impairment. Creatinine clearance values of 20 to 30 mL/min signify moderate renal impairment values of less than 10 mL/min signify several renal impairment. 

In Equation 1.36, Dg is the adjusted maintenance dose for the patient with renal failure, D is the maintenance dose for a normal individual,/is the fraction excreted, and C/r is the patient s creatinine clearance, which can be determined from the serum creatinine value using the Cockcroft and Gault Equation 1.42. If a new dosing interval for the patient with renal failure (x ) is calculated, a reciprocal of the bracketed term in Equation 1.45 is used and the new equation becomes Equation 1.46. ... 

This equation estimates Cl< in ml/min, which is a patient-specific value. This is what would be used in the prospective equation to estimate the elimination rate. Some of the other methods of estimating creatinine clearance compute an estimate that is normalized to a standard body surface area, usually 1.73 m. These estimates would need to be unnormalized to estimate a patient-specific elimination rate. To normalize a Cl estimate ... 

Renal function can be measured in several ways. The most common method involves determining circulatory levels and excretion of creatinine or creatinine clearance. Creatinine is formed from muscle metabolism in the body and circulates in the plasma of individuals with normal renal function at a concentration of approximately 1 mg%. Creatinine is cleared via kidneys by filtration to yield a creatinine clearance of approximately 130 mL min . This value depends partially on body size, degree of activity, muscle mass and age. 

Generally, a normal creatinine clearance value indicates that the kidney is functioning normally. 

Clearance determinations discussed so far all require measurement of concentrations in carefully timed urine and plasma samples. In addition, useful approximations to relative solute clearance values can be obtained by simplified procedures. The best known of these simply takes the plasma level of urea, or preferably creatinine, as a measure of the GFR. Indeed, if creatinine excretion (UV in g/day) is constant, the GFR (=UV/P) theoretically is inversely proportional to Pcr/ the creatinine concentration is plasma any increase in P r above a normal level of around 1 mg/dl should therefore reflect a corresponding fall in GFR. In practice the method is not very sensitive in the normal range of plasma creatinine levels (<1.4 mg/dl) a better correlation between measured creatinine clearance (Cc) and that predicted on the basis of Pcr is obtained at higher plasma levels, that is, lower Gcr values [6,21]. 

Initially the results were inspected for anomalies and results on consecutive days were then examined for differences. No significant differences were present between the values on the two consecutive days for both the normal diet and the low purine diet with regard to either urine volume, urate or creatinine excretion and urate or creatinine clearance. 

The clinical case of this xanthinuric man has been reported by DELBARRE in a previous paper (to be published). This man is a pastry cook since he could not be in the hospital more than one or two days, most determinations were done without control diet. This explains the great difference of daily urinary oxypurine values that were found. This patient has normal renal function (creatinine clearance = 99 ml/min). His averaged uric acid and oxypurines (xanthine and hypoxanthine) plasma concentration were 1.2 and 0.58 mg per 100 ml. His 95 % range ( mean + 2s) urinary excretion of uric acid is 7 to 27 mg per day and of oxypurine 310 to 618 mg... 

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