KIDNEY FUNCTION TEST Flashcards
This is responsible for the reabsorption of:
Sodium
Chloride
Bicarbonate and other ions
Glucose
Amino acids
Proteins
Urea and
Uric Acid
Proximal Convoluted Tubule
Renal Function Panel:
Glucose
BUN
Creatinine
Sodium
Potassium
Chloride
Phosphorus
Calcoum
Albumin
CO2
Elimination of Waste products
Maintenance of blood volume
Maintenance of electrolyte balance
Maintenance of acid-base balance
Endocrine function (EPO secretion)
Functions of the Kidneys
Measure of clearance of normal molecules that are not bound to protein and are freely filtered by the glomeruli neither reabsorbed nor secreted by the tubules
Glomerular Filtration Rate
GFR is considered the best ___
Overall indicator of level of Kidney function
Removal of substance from plasma into urine over a fixed time
Expressed in mL/minute
Clearance
Plasma concentration is _____ to clearance
Inversely proportional
Formula for Clearance:
(Urine/Plasma) x (Volume/1440) x (1.73/A)
Reference Method
Inulin Clearance
Not routinely done
Reference Method
Inulin Clearance
Not routinely done
Reference Value of Inulin Clearance
Male = 127 mL/min
Female = 118 mL/min
Provides an estimate of the amount of plasma that must flowed through the kidney glomeruli per minute
Excellent measure of renal function
Creatinine Clearance
Creatinine is freely filtered by the glomeruli but not reabsorbed
Provides an estimate of the amount of plasma that must flowed through the kidney glomeruli per minute
Excellent measure of renal function
Creatinine Clearance
Creatinine is freely filtered by the glomeruli but not reabsorbed
Reference Value of Creatinine Clearance
Male: 85-125 mL/min
Female: 75-112 mL/min
- High Cardiac Output
- Pregnancy
- Burns
- CO poisoning
Increased Creatinine Clearance
- Impaired Kidney Function
- Shock, Dehydration
- Hemorrhage
- Congestive Heart Failure
Decreased Creatinine Clearance
Can demonstrate progression of renal disease or response to therapy
Not give reliable estimates of the GFR since it is freely filtered by the glomeruli but variably reabsorbed by the tubules
Urea Clearance
Volume depletion decreases Urea Clearance by both:
Reduced Filtration
Increased Reabsorption
Produced at a constant rate by all nucleated cells
Freely filtered at glomerulus, not secreted by the renal tubules but reabsorbed
Cystatin C
Increases more rapidly than creatinine in the early stages of GFR impairment
Cystatin C
Reference Value of Cystatin C
Adult: 0.5-1.9 mg/L
(>65 yo): 0.9-3.4 mg/L
Low molecular weight glycoprotein
Functions as Prostaglandin D Synthase
Isolated primarily from CSF; Freely filtered at Glomerulus, then reabsorbed completely and catabolized by the proximal tubule
Beta Trace Protein
Major end product of Protein and Amino Acid Catabolism
Synthesized in Liver from CO2 and Ammonia from deamination of AA
Glomerulus: Freely filtered
PCT: Substantially reabsorbed
**First Metabolite to Elevate in Kidney Disease
Easily removed by Dialysis
Blood Urea Nitrogen
Reference Value of BUN
8-23 mg/dL
BUN:Creatinine Ratio
10:1
20:1
End Product: Yellow Diazine Derivative
Diacetyl Monoxime Method
Chemical Method
BUN
End Product: NH3 + CO2
Hydrolysis of Urea by Urease
Enzymatic Method (Indirect)
BUN
End: Glutamate + NAD + H2O
Coupled Urease or
Glutamate Dehydrogenase Method
UV Enzymatic Method
BUN
End: Glutamate + NAD + H2O
Coupled Urease or
Glutamate Dehydrogenase Method
UV Enzymatic Method
BUN
Reference Method for BUN
Isotope Dilution Mass Spectrometry (IDMS)
- Chronic Renal Disease
- Stress
- Burns
- High Protein Diet
- Dehydration
Increased BUN
- Poor Nutrition
- Hepatic Disease
- Impaired Absorption (Celiac Dse)
- Pregnancy
Decreased BUN
End Product of Muscle Metabolism derived from creatine
Partially secreted by PCT via organic cation transport pathway
Not reused in body’s metabolism, solely as a waste product
Commonly used to monitor renal function; index of overall renal function
Creatinine
Measure of the completeness of 24-hour urine collection
Used to evaluate fetal kidney maturity
Creatinine
Reference Value of Creatinine
Male: 0.9-1.3 mg/dL
Female: 0.6-1.1 mg/dL
Patients taking this antibiotics may have falsely increased result in Jaffe reaction:
Cephalosporin
A Red-Orange tautomer of creatinine picrate is formed when creatinine is mixed with alkaline picrate reagent
Direct Jaffe Method
False Increased Direct Jaffe
Ascorbate
Glucose
Uric Acid
A-Keto acids