Urine creatinine concentration

Direct measurement of creatinine clearance (CrCl) requires collection of urine over an extended time interval (usually 24 hours) with measurement of urine volume, urine creatinine concentration, and serum creatinine concentration (Table 22-1). Because kidney function can fluctuate significantly during ARF, this method may underestimate or overestimate kidney function depending on whether ARF is worsening or resolving. 

Ucr = urine creatinine concentration, mg/dL V = volume of urine, mL Scr = serum creatinine concentration, mg/dL T = time of urine collection, minute (Note time equals 1440 minutes for a 24-hour collection)... 

The urine creatinine concentration should be used to normalize the quantity of any analyte of interest, as this will correct for incomplete urine collection or urine dilution that may have resulted from drinking water spillage within the metabolism cages (Haas et al. 1997). The quantity of creatinine in a spot urine sample serves as an accurate index of the 24 hour urine output in most species. 

Normalization of Cannabinoid Urine Concentrations to Urine Creatinine Concentrations... 

The creatinine clearance is calculated using the formula below where U is the urine creatinine concentration, V is the urine flow-rate and P is the plasma or serum creatinine concentration. As there are 1440 minutes in a day this man s urine flow-rate, V = 2160 / 1440 =... 

While some clinical and laboratory findings assist in the general diagnosis of ARF, others are used to differentiate between prerenal, intrinsic, and postrenal ARF. For example, patients with prerenal ARF typically demonstrate enhanced sodium reabsorption, which is reflected by a low urine sodium concentration and a low fractional excretion of sodium. Urine is typically more concentrated with prerenal ARF and there is a higher urine osmolality and urine plasma creatinine ratio compared to intrinsic and postrenal ARF. 

Under field exposure conditions, it is recommended to measure PA herbicides in 24-hr urine samples collected starting at the end of the work-shift. Spot samples collected at the end of exposure or the following morning can be used when a 24-hr urine collection is impractical. In this case, the concentration of the compounds should be normalized to creatinine concentration or adjusted for specific gravity. 

The serum creatinine concentration of a human volunteer was found to be 1.2 mg/dL. Over a 24-hour period, 1.6 L of urine was collected and the concentration of creatinine in urine was found to be 98 mg/dL. What is the creatinine clearance of the volunteer ... 

Write down the information provided and use the appropriate formula. Creatinine concentration in urine (Cu) = 98 mg/dL... 

Kidney Failure, Acute A clinical syndrome characterized by a sudden decrease in glomerular filtration rate, often to values of less than 1 to 2 ml per minute. It is usually associated with oliguria (urine volumes of less than 400 ml per day) and is always associated with biochemical consequences of the reduction in glomerular filtration rate such as a rise in blood urea nitrogen (BUN) and serum creatinine concentrations. [NIH]... 

Neonates have diminished nicotine metabolism, as demonstrated by a nicotine half-life of three to four times longer in newborns exposed to tobacco smoke than in adnlts (Dempsey et al. 2000). Cotinine half-life is reported to be similar in neonates, older children, and adults in two studies (Dempsey et al. 2000 Leong et al. 1998). Other studies found that the half-life of urine cotinine was about three times longer in children less than one year old than to the cotinine half-life in adults (Collier et al. 1994). Urine cotinine half-life can be influenced by variations in urine volume and excretion of creatinine. The study by Dempsey et al. was the only one in which the half-life of cotinine was calculated based on both the blood and urine cotinine concentrations (Dempsey et al. 2000). In that study, both the blood and urine half-lives were similar to adult values, supporting the notion that neonates have the same cotinine half-life as older children and adults. 

Apply the same reasoning to this as to the level (concentration) of any other substance in the blood -be it a drug or an endogenous chemical. An unchanging plasma creatinine means, if volume of distribution is unchanged, that input equals loss from the plasma into the urine. Creatinine comes from creatine released continuously from our muscles. In old age muscle mass is less, and the input of creatine... 

Obtain the creatinine concentration (mg/dl) on the specimen to be analyzed. Determine the amount of urine equivalent to 0.25 mg creatinine. If the creatinine value is <8 mg/dl, extract 3.0 ml of urine. 

Acylcarnitine analysis was first performed in urine specimens in the evaluation of patients with organic acidemias. However, because it was found that acylcarnitine analysis of plasma is more informative for the diagnosis of FAO disorders than analysis of urine specimens, plasma has become the preferred specimen [17]. It is only recently that it was shown that urine acylcarnitine analysis still has a role in the diagnostic evaluation of patients with organic acidurias but uninformative or borderline abnormal results of plasma acylcarnitine and urine organic acid analysis [18-21]. In our laboratory, sample preparation and analysis is identical to that of plasma once a urine aliquot has been prepared that is based on the creatinine concentration. 

The creatinine concentration is measured in the sample using routine methods (i.e., the Jaffe reaction). A urine volume equivalent to 0.25 mg creatinine is diluted to 300 pi with deionized water (if the creatinine equivalent exceeds 300 pi, no dilution is made). A 20-pl aliquot of the diluted or undiluted urine is then analyzed following the procedure described above for plasma acylcarnitine analysis (section 3.2.4). The final result is expressed as mmol/mol creatinine. 

Un-timed urine specimens are used for this assay. Early-morning urine should be discarded because GAG excretion referred to creatinine concentration is increased during the night. During the day, the GAGicreatinine ratio remains fairly constant... 

Different amounts of urine are used depending on the creatinine concentration. We use 200 pi urine when creatinine <1.0 mmol/1 100 pi urine when creatinine lies between 1.0 and 10.0 mmol/1 50 pi urine when creatinine > 10.0 mmol/1. Distilled water is added to obtain a total volume of 200 pi. 13C4-Erythritol (2.5 nmol), 13C2-arabitol (50 nmol) and D3-sorbitol (10 nmol) are added as the IS. Pre-treated amberlite MB3 (20 pg) is added, mixed and centrifuged for 5 minutes at 410 xg. The supernatant is stored at -20°C until injection. 

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