Part 2: Renal Physiology and Renal Function Tests Flashcards
Glomerular Filtration Rate
Measures the rate at which kidneys can remove or clear a filterable substance from the blood
Clearance Test
Glomerular Filtration Rate
→ Removal of a substance from plasma into urine over a fixed period
→ Not bound to proteins
→Filtered, neither reabsorbed nor secreted
Clearance Test
Glomerular Filtration Rate:Clearance Test
In clearance test, if the marker is something that is reabsorbed, what would happen to the volume?
the current volume over the fixed period of time would not be measured
Glomerular Filtration Rate: Clearance Test
In clearance test, if the marker is something that is secreted, what would happen to the volume?
amount would not be fixed (would increase)
Glomerular Filtration Rate: Clearance Test
Unit?
milliliters/minute
Glomerular Filtration Rate: Clearance Test
Markers?
Exogenous and Endogenous substance
Glomerular Filtration Rate: Clearance Test
A high GFR in clearance test means there is?
Efficient excretion
Glomerular Filtration Rate: Clearance Test
A low GFR in clearance test means there is?
Inefficient excretion
Glomerular Filtration Rate: Clearance Test
What is the formula for clearance test?
U X V / P
→ U = urine concentration of the marker
→ P = plasma concentration of the marker
→ V = total urine volume (24-hr sample)
→A = patient’s body surface area
Formula for Clearance Test
What is the average bodu surface area (A)
1.73 m2
Shows the body surface area of an individual
Nomogram
If you see this card review the image of the nomogram
Go na
Marker
→ Substances that are not naturally produced in the body
→ Needs to be administered
Exogenous
Type of Marker: Exogenous
What are the markers under exogenous
- Inulin
- Radioactive markers
Type of Marker: Exogenous
→ Reference method
→ Not routinely done
→ Soluble, freely, filtered, neither secreted nor reabsorbed
Inulin
Type of Marker: Exogenous
Inulin value for male?
Male: 127mL/min/1.73m2
Type of Marker: Exogenous
Inulin value for female?
118 ml/min/1.73m2
Type of Marker: Exogenous
What are the example of radioactive markers?
- 125I-iothalamate
- 99m Tc-DTPA
- Iohexol
- 51Cr-EDTA
Marker
Naturally produced in the body
Endogenous
Marker: Endogenous
A common type of marker under endogenous
- Creatinine Clearance (Ccrea)
Marker: Endogenous
Waste product of muscle metabolism that is produced enzymatically by creatine phosphokinase from creatine
Creatinine
Marker: Endogenous
What enzyme produces creatinine and where?
Creatinine phosphokinase from creatine
Marker: Endogenous
Normal values of Creatinine Clearance for female?
75 - 112 ml/min
Marker: Endogenous
Normal values of Creatinine Clearance for male?
85 - 125 ml/min
T or F
Males have lower value in creatinine clearance since they have less muscle mass
F (opposite; males have higher value since they have more muscle mass)
Familiarize the disadvantages of creatinine clearance
- Some creatinine is secreted by the tubules
- Chromogens in plasma react in the chemical analysis
- Medications inhibit tubular secretion
- Bacteria break down urinary creatinine
- A diet heavy in meat can raise creatinine
- Not a reliable indicator in patients suffering from muscle-wasting diseases
- Depends on the completeness of a 24-hour collection
- It must be corrected for BSA (unless normal)
T or F
Glomerular Filtration Tests
Greatest source of error in any clearance procedure using urine
Improperly timed urine specimens
Glomerular Filtration Tests
What are the methods that do not require the collection of timed (24-hour) urine specimens
- Estimated glomerular filtration rate eGFR using serum creatinine
- Cystatin C
- Beta2-microglobulin
What are the 3 methods in Calculated Glomerular Filtration Estimate?
- Cockcroft & Gault
- Modification of Diet in Renal Disease (MDRD)
- Chronic Kidney Disease Epidemiology Collaboration CKD-EPI (2021)
3 methods in Calculated Glomerular Filtration Estimate
Variables: Age, Sex, Weight (Kg)
Cockcroft & Gault
3 methods in Calculated Glomerular Filtration Estimate
Formula for Cockcroft & Gault
(140 - age) (wt in kg) / 72 x Serum crea in mg/dl)
x 0.85 if female
3 methods in Calculated Glomerular Filtration Estimate
6 Variables (previous): Age, Sex, Serum urea nitrogen, Serum creatinine, Race, and Serum albumin
Simplified MDRD based on four variables: Serum creatinine, Age, Race, and Sex
Modification of Diet in Renal Disease (MDRD)
3 methods in Calculated Glomerular Filtration Estimate
Formula for Modification of Diet in Renal Disease (MDRD)
GFR = 173 X Serum creatinine^1.154 x Age^-0.203 x 0.742 (if patient is female) x 1.212 (if patient is black)
3 methods in Calculated Glomerular Filtration Estimate
→ Recommended formula by the National Kidney Disease Education Program (NKDEP)
→ Serum creatinine obtained with an enzymatic IDMS-traceable assay
→ Correspond more closely to the isotope dilution mass spectrophotometry (IDMS)
→ More accurate and precise when telling the status of the patient’s kidney
MDRD-IDMS-traceable formula
3 methods in Calculated Glomerular Filtration Estimate
MDRD-IDMS-traceable formula
GFR = 175 X Serum creatinine^-1.154 x Age^-0.203 x 0.742 (if patient is female) x 1.212 (if patient is black)
3 methods in Calculated Glomerular Filtration Estimate
→ Estimates GFR from serum creatinine, age, sex
→ Formerly race was included
Chronic Kidney Disease Epidemiology Collaboration CKD-EPI (2021)
3 methods in Calculated Glomerular Filtration Estimate
Familiarize the formula for Chronic Kidney Disease Epidemiology Collaboration CKD-EPI (2021)
please look at the ppt or trans tinatamad ako itype
3 methods in Calculated Glomerular Filtration Estimate
Normal Reference Range:
Stage 1 GFR =
Stage 1 GFR = greater than 90 mL/min/1.73