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Creatinine: Difference between revisions
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'''Creatinine''' is a breakdown product of [[creatine]] phosphate following the [[creatine kinase]] reaction. Its significance in medicine is its use as a marker of kidney excretory function; more specifically, it's used to calculate the [[Kidney function tests|estimated glomerular filtration rate]] (eGFR), an estimate of the true [[glomerular filtration rate]] (GFR) when evaluating the kidney function. Creatinine and estimated glomarular filtration rate are extensively used in the evaluation of [[chronic kidney disease]] (CKD) and [[acute kidney injury]] (AKI). | <section begin="clinical biochemistry" />'''Creatinine''' is a breakdown product of [[creatine]] phosphate following the [[creatine kinase]] reaction. Its significance in medicine is its use as a marker of kidney excretory function; more specifically, it's used to calculate the [[Kidney function tests|estimated glomerular filtration rate]] (eGFR), an estimate of the true [[glomerular filtration rate]] (GFR) when evaluating the kidney function. Creatinine and estimated glomarular filtration rate are extensively used in the evaluation of [[chronic kidney disease]] (CKD) and [[acute kidney injury]] (AKI). | ||
The normal range of creatinine is approximately 60 - 100 ''µmol/L.'' | The normal range of creatinine is approximately 60 - 100 ''µmol/L.'' | ||
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Creatinine is eliminated by the kidneys by [[glomerular filtration]] (and to a smaller degree [[tubular secretion]]). It is normally not reabsorbed in the tubuli, except when there is [[oliguria]]. The rate at which blood plasma is cleared of creatine is called the [[creatinine clearance]]. Because creatinine is freely filtered in the glomeruli and is only secreted in the tubuli to a small degree, the creatinine clearance is approximately equal to the glomerular filtration rate. | Creatinine is eliminated by the kidneys by [[glomerular filtration]] (and to a smaller degree [[tubular secretion]]). It is normally not reabsorbed in the tubuli, except when there is [[oliguria]]. The rate at which blood plasma is cleared of creatine is called the [[creatinine clearance]]. Because creatinine is freely filtered in the glomeruli and is only secreted in the tubuli to a small degree, the creatinine clearance is approximately equal to the glomerular filtration rate. | ||
1-2% of free creatine phosphate in skeletal muscle is broken down to creatinine daily. The rate of production depends on the muscle mass of the individual; the higher the mass, the higher the production. Serum creatinine levels are approx 30% higher in the evening than in the morning, likely due to muscle movement during the day. | 1-2% of free creatine phosphate in skeletal muscle is broken down to creatinine daily. The rate of production depends on the muscle mass of the individual; the higher the mass, the higher the production. Serum creatinine levels are approx 30% higher in the evening than in the morning, likely due to muscle movement during the day.<section end="clinical biochemistry" /> | ||
== Estimated glomerular filtration rate == | == Estimated glomerular filtration rate == | ||