Information about Glomerular Filtration Rate
This article is about a measure of kidney function (GFR) and its estimated value (eGFR). For the cell suface receptor EGFR, see Epidermal growth factor receptor.
Glomerular filtration rate (GFR) is the volume of fluid filtered from the renal (kidney) glomerular capillaries into the Bowman's capsule per unit time.[1] Clinically, this is often measured to determine renal function. Compare to filtration fraction.
Measurement
There are several different techniques used to calculate or estimate the glomerular filtration rate (GFR or eGFR).Measurement using inulin
The GFR can be determined by injecting inulin (not insulin) into the plasma. Since inulin is neither reabsorbed nor secreted by the kidney after glomerular filtration, its rate of excretion is directly proportional to the rate of filtration of water and solutes across the glomerular filter.Estimation using creatinine clearance
In clinical practice, however, creatinine clearance is used to measure GFR. Creatinine is an endogenous molecule, synthesized in the body, which is freely filtered by the glomerulus (but also secreted by the renal tubules in very small amounts). Creatinine clearance is therefore a close approximation of the GFR. However, the approximation of the GFR calculation is best measured by the evaluation and visualization of the frequency and duration of urination. The GFR is typically recorded in units of volume per time, e.g. milliliters per minute (ml/min).Example: A person has a plasma creatinine concentration of 0.01 mg/ml and in 1 hour he excretes 75 mg of creatinine in the urine. The GFR is calculated as M/P (where M is the mass of creatinine excreted per unit time and P is the plasma concentration of creatinine).
Estimation using Cockcroft-Gault formula
The Cockcroft-Gault formula may be used to calculate an Estimated Creatinine Clearance, which in turn estimates GFR:[2]
Modification of Diet in Renal Disease (MDRD) formula
The most commonly used formula is the "4-variable MDRD" which estimates GFR using four variables: serum creatinine, age, race, and gender.[3] The original MDRD used six variables with the additional variables being the blood urea nitrogen and albumin levels.[4] The equations have been validated in patients with chronic kidney disease; however both versions underestimate the GFR in healthy patients with GFRs over 60 mL/min.[5][6] The equations have not been validated in acute renal failure.
Calculation using Starling equation
It is also theoretically possible to calculate GFR using the Starling equation.[7]
The equation is used both in a general sense for all capillary flow, and in a specific sense for the glomerulus:
| General usage | Glomerular usage | Meaning of variable | Relationship to GFR | Description |
| Pc | Pgc | Capillary hydrostatic pressure | Direct | Increased by dilation of afferent arteriole or constriction of efferent arteriole |
| Pi | Pbs | Interstitial hydrostatic pressure | Inverse | |
| πc | πgc | Capillary oncotic pressure | Inverse | Decreased by nephrotic syndrome |
| πi | πbs | Interstitial oncotic pressure | Direct | |
| Kf | Kf | Filtration coefficient | Direct | Increased by inflammation |
| σ | σ | Reflection coefficient | Inverse | |
| Jv | GFR | net filtration | n/a |
Note that
is the net driving force, and therefore the net filtration is proportional to the net driving force.
In practice, it is not possible to identify the needed values for this equation, but the equation is still useful for understanding the factors which affect GFR, and providing a theoretical underpinning for the above calculations.
Normal ranges
The normal ranges of GFR, adjusted for body surface area, are:[8]- Males: 70 ± 14 mL/min/m2
- Females: 60 ± 10 mL/min/m2
See also
References
1. ^ Physiology at MCG 7/7ch04/7ch04p11 - "Glomerular Filtration Rate"
2. ^ GFR Calculator at cato.at - Cockcroft-Gault - GFR calculation (Cockcroft-Gault formula)
3. ^ (2002) "K/DOQI clinical practice guidelines for chronic kidney disease: evaluation, classification, and stratification". Am. J. Kidney Dis. 39 (2 Suppl 1): S1–266. PMID 11904577.
4. ^ Levey AS, Bosch JP, Lewis JB, Greene T, Rogers N, Roth D (1999). "A more accurate method to estimate glomerular filtration rate from serum creatinine: a new prediction equation. Modification of Diet in Renal Disease Study Group". Ann. Intern. Med. 130 (6): 461–70. PMID 10075613.
5. ^ Rule AD, Larson TS, Bergstralh EJ, Slezak JM, Jacobsen SJ, Cosio FG (2004). "Using serum creatinine to estimate glomerular filtration rate: accuracy in good health and in chronic kidney disease". Ann. Intern. Med. 141 (12): 929–37. PMID 15611490.
6. ^ Levey AS, Coresh J, Greene T, et al (2006). "Using standardized serum creatinine values in the modification of diet in renal disease study equation for estimating glomerular filtration rate". Ann. Intern. Med. 145 (4): 247–54. PMID 16908915.
7. ^ Physiology at MCG 7/7ch04/7ch04p12 - "Forces Driving the Glomerular Filtration Rate":
8. ^ Creatinine clearance at merck.com - The normal ranges of GFR.
2. ^ GFR Calculator at cato.at - Cockcroft-Gault - GFR calculation (Cockcroft-Gault formula)
3. ^ (2002) "K/DOQI clinical practice guidelines for chronic kidney disease: evaluation, classification, and stratification". Am. J. Kidney Dis. 39 (2 Suppl 1): S1–266. PMID 11904577.
4. ^ Levey AS, Bosch JP, Lewis JB, Greene T, Rogers N, Roth D (1999). "A more accurate method to estimate glomerular filtration rate from serum creatinine: a new prediction equation. Modification of Diet in Renal Disease Study Group". Ann. Intern. Med. 130 (6): 461–70. PMID 10075613.
5. ^ Rule AD, Larson TS, Bergstralh EJ, Slezak JM, Jacobsen SJ, Cosio FG (2004). "Using serum creatinine to estimate glomerular filtration rate: accuracy in good health and in chronic kidney disease". Ann. Intern. Med. 141 (12): 929–37. PMID 15611490.
6. ^ Levey AS, Coresh J, Greene T, et al (2006). "Using standardized serum creatinine values in the modification of diet in renal disease study equation for estimating glomerular filtration rate". Ann. Intern. Med. 145 (4): 247–54. PMID 16908915.
7. ^ Physiology at MCG 7/7ch04/7ch04p12 - "Forces Driving the Glomerular Filtration Rate":
8. ^ Creatinine clearance at merck.com - The normal ranges of GFR.
External links
- National Kidney Disease Education Program website. Includes professional references and GFR calculators
- Online GFR Calculator using MDRD, Gault, and Combo Also shows GFR expected for age and current GFR percentage of expected.
- Online GFR Calculator (Cockcroft-Gault Formula)
- Online GFR Calculator - AnaemiaWorld.com
- REN70 at FPnotebook
Urinary system, physiology: renal physiology and acid base physiology | |
|---|---|
| Filtration | Ultrafiltration - Countercurrent exchange |
| Hormones affecting filtration | Antidiuretic hormone (ADH) - Aldosterone - Atrial natriuretic peptide |
| Endocrine | Renin - Erythropoietin (EPO) - Calcitriol (Active vitamin D) - Prostaglandins |
| Assessing Renal function / Measures of dialysis | Glomerular filtration rate - Creatinine clearance - Renal clearance ratio - Urea reduction ratio - Kt/V - Standardized Kt/V - Hemodialysis product |
| Acid base physiology | Fluid balance - Darrow Yannet diagram - Body water - Interstitial fluid - Extracellular fluid - Intracellular fluid/Cytosol - Plasma - Transcellular fluid - Base excess - Davenport diagram - Anion gap |
| Buffering/compensation | Bicarbonate buffering system - Respiratory compensation - Renal compensation |
epidermal growth factor receptor (EGFR; ErbB-1; HER1 in humans) is the cell-surface receptor for members of the epidermal growth factor family (EGF-family) of extracellular protein ligands.
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The kidneys are organs that filter wastes (such as urea) from the blood and excrete them, along with water, as urine. The medical field that studies the kidneys and diseases of the kidney is called nephrology[1].
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glomerulus is a capillary tuft surrounded by Bowman's capsule in nephrons of the vertebrate kidney. It receives its blood supply from an afferent arteriole of the renal circulation.
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The Bowman's capsule(other names: capsula glomeruli, glomerular capsule) is a cup like sac at the beginning of the tubular component of a nephron in the mammalian kidney. A glomerulus is enclosed in the sac.
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In medicine (nephrology) renal function is an indication of the state of the kidney and its role in physiology.
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Indirect markers
Most doctors use the plasma concentrations of creatinine, urea, and electrolytes to determine renal function...... Click the link for more information.
In renal physiology, the filtration fraction is the ratio of the glomerular filtration rate (GFR) to the renal plasma flow (RPF).
> Filtration Fraction = GFR/RPF re>
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> Filtration Fraction = GFR/RPF re>
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- ''Note: This article title may be easily confused with insulin.
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In general, creatinine clearance is the removal of creatinine from the body. In renal physiology, creatinine clearance (CCr) is the volume of blood plasma that is cleared of creatinine per unit time.
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blood urea nitrogen (BUN) test is a measure of the amount of nitrogen in the blood that comes from urea. Urea is a substance secreted by the liver, and removed from the blood by the kidneys.
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You may be looking for albumen, or egg white.
Albumin (Latin: albus, white) refers generally to any protein with water solubility, which is moderately soluble in concentrated salt solutions, and experiences heat coagulation (protein denaturation).
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Albumin (Latin: albus, white) refers generally to any protein with water solubility, which is moderately soluble in concentrated salt solutions, and experiences heat coagulation (protein denaturation).
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Formulated in 1896 by the British physiologist Ernest Starling, the Starling equation illustrates the role of hydrostatic and oncotic forces (the so-called Starling forces) in the movement of fluid across capillary membranes.
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The afferent arterioles are a group of blood vessels that supply the nephrons in many excretory systems.
The afferent arterioles branch from the renal artery which supplies blood to the kidneys.
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The afferent arterioles branch from the renal artery which supplies blood to the kidneys.
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The efferent arterioles are blood vessels that are part of the urinary system of many animals. The efferent arterioles form from a convergence of the capillaries of the glomerulus.
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oncotic pressure. Because large plasma proteins cannot easily cross through the capillary walls, their effect on the osmotic pressure of the capillary interiors will, to some extent, balance out the tendency for fluid to leak out of the capillaries.
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Nephrotic syndrome
Classification & external resources
ICD-10 N 04.
ICD-9 581.9
DiseasesDB 8905
eMedicine med/1612 ped/1564
MeSH D009404
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Classification & external resources
ICD-10 N 04.
ICD-9 581.9
DiseasesDB 8905
eMedicine med/1612 ped/1564
MeSH D009404
- Not to be confused with nephritic syndrome
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Inflammation (Latin, inflammatio, to set on fire) is the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants.
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MeSH D007019 Hypoproteinemia (or "Hypoproteinaemia") is a condition where there is an abnormally low level of protein in the blood.
One common cause is due to excess protein in the urine (proteinuria), which can be a medical sign of nephrotic syndrome.
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One common cause is due to excess protein in the urine (proteinuria), which can be a medical sign of nephrotic syndrome.
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The efferent arterioles are blood vessels that are part of the urinary system of many animals. The efferent arterioles form from a convergence of the capillaries of the glomerulus.
..... Click the link for more information.
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The afferent arterioles are a group of blood vessels that supply the nephrons in many excretory systems.
The afferent arterioles branch from the renal artery which supplies blood to the kidneys.
..... Click the link for more information.
The afferent arterioles branch from the renal artery which supplies blood to the kidneys.
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MeSH C12.777.419.780.500 Renal failure or kidney failure is the condition in which the kidneys fail to function adequately.
Biochemically, it is typically detected by an elevated serum creatinine.
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Biochemically, it is typically detected by an elevated serum creatinine.
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dialysis is primarily used to provide an artificial replacement for lost kidney function (renal replacement therapy) due to renal failure. Dialysis may be used for very sick patients who have suddenly but temporarily, lost their kidney function (acute renal failure) or for quite
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In the physiology of the kidney, tubuloglomerular feedback (TGF) is one of several mechanisms the kidney uses to regulate glomerular filtration rate (GFR). Changes in GFR are detected by the renal tubule, which sends feedback signals to the glomerulus, initiating a cascade
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In renal physiology, the filtration fraction is the ratio of the glomerular filtration rate (GFR) to the renal plasma flow (RPF).
> Filtration Fraction = GFR/RPF re>
..... Click the link for more information.
> Filtration Fraction = GFR/RPF re>
..... Click the link for more information.
Medical College of Georgia is the smallest of four research schools in the University System of Georgia (USG). MCG currently has 5 undergraduate and graduate schools on campus: The School of Medicine, School of Dentistry, School of Nursing, School of Allied Health, and Graduate
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Medical College of Georgia is the smallest of four research schools in the University System of Georgia (USG). MCG currently has 5 undergraduate and graduate schools on campus: The School of Medicine, School of Dentistry, School of Nursing, School of Allied Health, and Graduate
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The Family Practice Notebook is a medical database focused on family practice.
It is maintained by Scott Moses, MD, a physician from Minnesota.
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It is maintained by Scott Moses, MD, a physician from Minnesota.
External links
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The urinary system is the organ system that produces, stores, and eliminates urine. In humans it includes two kidneys, two ureters, the bladder, and the urethra. The analogous organ in invertebrates is the nephridium.
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Human physiology is the science of the mechanical, physical, and biochemical functions of humans in good health, their organs, and the cells of which they are composed. The principal level of focus of physiology is at the level of organs and systems.
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Renal physiology is the study of the physiology of the kidneys.
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Functions of the kidney
The functions of the kidney can be divided into two groups: secretion of hormones, and extracellular homeostasis...... Click the link for more information.
Acid-base physiology is the study of the acids, bases and their reactions in the body. For survival, acid base homeostasis is an absolute requirement.
The traditional approach to the study of acid-base physiology has been the empiric approach.
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The traditional approach to the study of acid-base physiology has been the empiric approach.
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