Glomerular Filtration Rate (GFR)

A Glomerular Filtration Rate (GFR) is a renal function measure that quantifies kidney filtration and blood clearance (indicating renal function status).

• AKA: GFR Test, Glomerular Function Test, Kidney Filtration Rate, Renal Filtration Measure.
• Context:
  • It can typically measure Kidney Function through blood filtration rate.
  • It can typically evaluate Renal Health through glomerular performance.
  • It can typically indicate Disease Status through filtration efficiency.
  • It can typically guide Treatment Decision through function assessment.
  • It can typically monitor Disease Progression through sequential measurement.
  • ...
  • It can often detect Kidney Disease through early decline.
  • It can often assess Treatment Response through value change.
  • It can often predict Clinical Outcome through trend analysis.
  • It can often adjust Medication Dosage through clearance value.
  • ...
  • It can range from being a Normal GFR Reading to being an Impaired GFR Reading, depending on its filtration value.
  • It can range from being a Direct GFR Measurement to being an Estimated GFR Calculation, depending on its measurement method.
  • It can range from being a Single Time Point to being a Continuous Monitoring, depending on its assessment frequency.
  • ...
  • Measure Output: a GFR Reading Value in ml/min:
    • Normal Range: 90-120 ml/min
    • Mild Impairment: 60-89 ml/min
    • Moderate Impairment: 30-59 ml/min
    • Severe Impairment: 15-29 ml/min
    • Kidney Failure: <15 ml/min
  • ...
• Examples:
  • GFR Measurement Methods, such as:
    • Direct Measurements, such as:
      • Inulin Clearance for gold standard assessment.
      • Iothalamate Clearance for accurate measurement.
    • Estimated GFRs, such as:
      • MDRD Equation for adult assessment.
      • CKD-EPI Equation for improved accuracy.
  • GFR Clinical Applications, such as:
    • Disease Stagings, such as:
      • CKD Classification for disease severity.
      • Treatment Planning for intervention timing.
    • Monitoring Purposes, such as:
      • Disease Progression for kidney decline.
      • Treatment Response for function improvement.
  • ...
• Counter-Examples:
  • Serum Cystatin C Measure, which measures protein marker rather than filtration rate.
  • Blood Creatinine Measure, which measures waste product rather than clearance rate.
  • Urine Output Measure, which measures excretion volume rather than filtration capacity.
• See: Kidney Disease, Nephrology, Kidney, Renal Physiology, Blood Plasma, Creatinine, Cimetidine, Chronic Kidney Disease, Albuminuria, Renal Function, Filtration Process.

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References

2017

• (Wikipedia, 2017) ⇒ https://en.wikipedia.org/wiki/Renal_function#Glomerular_filtration_rate Retrieved:2017-5-8.
  • Glomerular filtration rate (GFR) is the volume of fluid filtered from the renal (kidney) glomerular capillaries into the Bowman's capsule per unit time. Central to the physiologic maintenance of GFR is the differential basal tone of the afferent and efferent arterioles (see diagram). In other words, the filtration rate is dependent on the difference between the higher blood pressure created by vasoconstriction of the input or afferent arteriole versus the lower blood pressure created lesser vasoconstriction of the output or efferent arteriole.

    Glomerular filtration rate (GFR) is equal to the Clearance Rate when any solute is freely filtered and is neither reabsorbed nor secreted by the kidneys. The rate therefore measured is the quantity of the substance in the urine that originated from a calculable volume of blood. Relating this principle to the below equation - for the substance used, the product of urine concentration and urine flow equals the mass of substance excreted during the time that urine has been collected. This mass equals the mass filtered at the glomerulus as nothing is added or removed in the nephron. Dividing this mass by the plasma concentration gives the volume of plasma which the mass must have originally come from, and thus the volume of plasma fluid that has entered Bowman's capsule within the aforementioned period of time. The GFR is typically recorded in units of volume per time, e.g., milliliters per minute mL/min. Compare to filtration fraction. : [math]\displaystyle{ GFR = \frac { \mbox{Urine Concentration} \times \mbox{Urine Flow} }{ \mbox{Plasma Concentration} } }[/math] There are several different techniques used to calculate or estimate the glomerular filtration rate (GFR or eGFR). The above formula only applies for GFR calculation when it is equal to the Clearance Rate.

2017

• (Wikipedia, 2017) ⇒ https://simple.wikipedia.org/wiki/Glomerular_filtration_rate Retrieved:2017-5-8.
  • Glomerular filtration rate (GFR) is a test used by physicians and other medical professionals to see if the kidneys are working correctly. In basic terms, it is a measurement of how much liquid and waste is passing from the blood through the tiny filters in the kidney, called the glomeruli, and out into the urine during each minute. The test measures how much creatinine is in the blood. This shows how well the kidneys are performing. In a normal healthy person the GFR stays close to the same value all of the time. The test is done by taking blood from a person and sending it to a laboratory. Normal values are between 90ml/min and 110ml/min. A value below 60ml/minute means the person has chronic renal disease and a value below 15ml/minute means the person's kidneys have stopped working.

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