Creatinine excretion

EssCOrr= corrected steady-state creatinine excretion Scr, = first serum creatinine concentration Scr2 = second serum creatinine concentration E = creatinine excretion... 

Analysis of the urinary data. The amount of creatinine and 3,5,6-TCP in each urine collection was calculated from the volume of the urine specimen and the concentration of each in that urine specimen. The amount of creatinine excreted per day was compared across days for each volunteer and to standard literature values for creatinine excretion (i.e., mean 1.8 g/24 hr 95% range, 1.1 to 2.5 g/24 hr). The urine collection was considered to be complete if the amount of creatinine was consistent with the amount of creatinine in the other urine specimens provided by that individual and within the literature range for normal creatinine excretion. 

With respect to amino acid excretion Woodson and co-workersl3 and othersl4,15 have found by microbiological methods large variations. Stein 16 obtained evidence of wide variations in the amino acid excretion of cystinurics. Further data are also available with respect to creatine and creatinine excretion which bear out our conclusion regarding individuality of excretion patterns. 17,18,19... 

Daily intake (mg/kg/day) = urinary concentration (mg/g creatine) x creatinine excretion (g/kg/day) x (monoester in urine (mol)/diester ingested (mol)) x (molecular weight of diester (g/mol)/molecular weight of monoester (g/mol)). 

Renal damage has been reported after both acute and chronic exposure. Mercury is known to accumulate in the kidneys, and case studies have described increased creatinine excretion, proteinuria, hematuria, and degeneration of the convoluted tubules in exposed individuals. Increased levels of the urinary enzyme NAG (AT-acetyl-P-glycosaminidase), compared with controls, have been observed in chronically exposed workers. ... 

Degradation Creatine and creatine phosphate spontaneously cyclize at a slow, but constant, rate to form creatinine, which is excreted in the urine. The amount of creatinine excreted is proportional to the total creatine phosphate content of the body, and thus can be used to estimate muscle mass. When muscle mass decreases for any reason (for example, from paralysis or muscular dystrophy), the creatinine content of the urine falls. In addition, any rise in blood creatinine is a sensitive indicator of kidney malfunction, because creatinine is normally rapidly removed from the blood and excreted. A typical adult male excretes about 15 mmol of creatinine per day. The constancy of this excretion is sometimes used to test the reliability of collected 24-hour urine samples—too little creatinine in the submitted sample may indicate an incomplete sample. 

Table 10.2 Daily Creatinine Excretion Per kg of Body Weight as Function of Age and Gender ...

Remer T, Neubert A, Maser-Gluth C. 2002. Anthropometry-based reference values for 24-h urinary creatinine excretion during growth and their use in endocrine and nutritional research. Am J Clin Nutr 75 561-569. 

Liu JX, Nordberg GF. 1995. Nephrotoxicities of aluminum and/or cadmium-metallothionein in rats Creatinine excretion and metabolism of selected essential metals. Pharmacol Toxicol 77 155-160. 

Some clinical chemists have found it suitable to adopt another unit basis of comparison, namely, a conventionally adopted amount of creatinine excretion. We feel that it is not advisable to encourage this procedure as one to be advocated as a standard for purposes of computation, particularly if it eventually becomes confirmed that creatinine excretion may not be as constant as it has been claimed to be, according to a recent publication (V7). In case the creatinine basis of reference is adopted, however, by certain workers, it is certainly highly desirable to indicate at the same time the urine volume output in 24 hours, the nitrogen output, as well as the creatinine output, and finally also the body weight. 

In children above 2 years of age, the situation is not substantially different from adults as far as the relative amounts of amino acids excreted are concerned. In fact, only very few really satisfactory data have been obtained so far in urines from children above 2 years of age. We present therefore in Fig. 3 a typical chromatogram of a 24-hr specimen of urine of a normal child, 2 years old, as drawn from Vis observations. Comparison of quantitative data concerning daily excretions are rendered difficult because of the differences in body size. The 24-hr basis alone is not suitable. It is necessary to compare data on the basis of percentage of total nitrogen excretion, or per kilogram of body weight, a procedure adopted by Jonxis and Huisman. We do not believe it suitable or safe to choose a comparison factor based on creatinine excretion. 

The urinary excretion kinetics of chromium have also been examined in eight adults that were administered chromium(III) at 400 pg/day as chromium(III) picolinate for 3 consecutive days (Gargas et al. 1994). The mean time to peak urinary concentration was 7.18 2.11 hours (range 2.9-13.0 hours), the mean peak concentration being 7.92 4.24 pg chromium/g creatinine (range 3.58-19.13 pg/g creatinine). Excretion diminished rapidly after the peak but did not appear to return to background in most of the volunteers before the next daily dose. 

While low serum cholesterol levels have been observed in malnourished patients, largely as a result of decreased synthesis of lipoproteins in the liver, hypocholesterolemia occurs later in the course of malnutrition and is therefore not useful as a screening test. PEM usually results in low serum urea nitrogen (BUN), urinary urea, and total nitrogen. Estimation of 24-h urine creatinine excretion is also a valuable biochemical index of muscle mass (when there is no impairment in renal function). The urinary CHI is correlated to lean body mass and anthropometric measurements. In edematous patients, for whom the extracellular fluids contribute to body weight and spuriously high body mass index values, the decreased CHI values are especially useful in diagnosing malnutrition. 

To eliminate the need for both complete timed urine collections (difficult to do in most animals) and concurrent assessment of GFR, FE values are usually calculated based on point-in-time urine collections by using creatinine excretion during the same time period as an estimator of GFR (Finco 1997). 

Either 24 hour urine collection or timed urine samples collected at the same time each day is recommended, with the activity expressed per unit of time (Price 1982, Plummer et al. 1986). If the assessment is to be repeated with time, the samples should be collected over the same time period on each day because there is pronounced diurnal variation in excretion rate of some enzymes (Maruhn et al. 1977, Price 1982, Gossett et al. 1987). For spot urine samples or those where accurate timed collection is not possible, normalization of activity per unit of creatinine can be done and this has been shown to be reasonably well correlated to 24 hour enzyme activity (Vanderlinde 1981, Grauer et al. 1995). Diet and age-matched controls must be included if enzyme activity is to be normalized to creatinine, to control for the effects of these variables on creatinine excretion (Plummer et al. 1986, Casadevall et al. 1995). 

The results of DPD/PYD measurements are usually normalized for the concentration of creatinine in urine, and presented as (nmol DPD(PYD)/mol of creatinine. This normalization will reduce the variability of results by elimination of the influence of diuresis, but the creatinine excretion itself exhibits individual biological variability of approximately 11% (R3). 

For plasma ammonia levels, whole blood was centrifuged and plasma pipetted into ammonia-free tubes. The plasma was then frozen immediately and kept frozen until ammonia was measured by an autoanalyzer. Urea nitrogen in the plasma and creatinine excretion in the urine were also measured by the autoanalyzer. Lactic dehydrogenase activity in the plasma was measured by a method published by Bergmeyer, Bernt, and Hess (10). Rlbonucle-ase activity was ascertained by a modified Seklne method (11,... 

If instead of looking at the rate of creatinine excretion in urine we consider the rate of change of creatinine in the body (dXjdt), we can write the following equation ... 

Gershoff et al. (G3) observed no significant differences, following the ingestion of 5 g DL-tryptophan, in N -methylnicotinamide and creatinine excretion, but xanthurenic acid was lower in mongoloids than in non-mongoloid mentally retarded children. 

Dystrophic muscle may contain only a tenth as much creatine as normal muscle (Rl), despite a suflBcient content of ADP and ATP (R9), due to its very low content of creatine kinase on which muscle creatine depends for its acceptance, retention, and use as creatine phosphate, since the total creatine content of dystrophic muscle is known to be directly proportional to the activity of the creatine kinase within it (R8). Excess creatine from the liver thus exceeds its renal threshold and is excreted in large amounts, while the low creatinine excretion indicates how slight is the remaining muscle function. 

These processes have been illustrated by the administration of glycine-N to a dystrophic patient (B12, R7), when the isotope content of the daily urinary creatinine excretion quickly reached a low, constant level, while that of creatine at the same time rose to a value some 10 times higher and took 11 days to sink again to the same level. The inter-... 

It should be noted that for urinary excretion studies the preferred design is to collect 24 h urine. In some special designs it can be argued that the use of spot urine samples and correction for urinary creatinine concentration may be a valid measure. A prerequisite for the spot urine - creatinine correction design is a solid argumentation that creatinine excretion is unchanged by the experimental condition or that it is not different between groups. A theoretical example is comparison of lean men versus fat females. Their cell number is comparable but muscle mass very different. Creatinine excretion is mainly... 

A fraction of urinary creatinine arises from the diet. Meat contains muscle and therefore contains creatine. Cookiitg meat results in the conversion of creatine to creatinine, which, after ingestion, is rapidly excreted into the urine. The human body generates and excretes about 1.7 g of creatinine per day. Dietary creatinine may reach (J 5 g per day. Thus, researchers studying creatinine excretion should control or limit meat intake by their subjects. 

Creatinine excretion is intimately related to a relatively constant part of the body, the muscle mass. When studying the excretion of any metabolite, such as urea, calcium, or riboflavin, it might be undesirable to relate the amount of urinary metabolite to bodily weight, because the body contains compartments that are of minimal importance relative to metabolism. The body of an obese person contains a large amount of tissue (adipose tissue) that is inetaboiicaUy and biochemically irrelevant to the metabolism of compounds such as urea, calcium, and riboflavin. A person w hosc body contains excess body fluids also has extra mass that may be irrelevant to the metabolism of these as W cll as other compounds A meaningful comparison of excretion data from different subjects or from one subject at different times is facilitated by relating the data to urinary creatinine. 

In all crises, the amount of metabolite is expressed per nfiilligram of creatinine excreted, rather than on a "per-volume" or "per-day" basis. Another reason for expressing excretion data in terms of creatinine is that, although a researcher might want to determine excretion data on a per-day basis, collection of an entire day s urinary output may be difficult or inconvenient. This difficulty can be overcome by using creatinine measurements. 

Walser, M. (1987). Creatinine excretion as a measure of protein nutrition in adults of varying age. /. Parenteral Enteral Nutr. 11,73S-78S. 

Creatinine in urine. The assay of creatinine in body fluids is one of the core assays in clinical chemistry since its level in blood and urine reflects the functional status of the kidney. There are many methods for its assay ranging from the simple colorimetric Jafle reaction to dedicated creatinine analysers using discrete sampling technologies. For many metabolic assays, the so-called creatinine correction can be applied since creatinine excretion is considered to be constant throughout the day. The clinic therefore only needs to collect a random specimen of urine rather than a full 24 h specimen. 

---