Renal Function Tests

• Urea clearance test


  __________________ - earliest and historical used to assess GFR
• inulin clearance test


  ________________ - gold standard for assessment of glomerular filtration rate
• creatinine clearance test


  ___ - most commonly used method to assess GFR
• 24 hour urine specimen and Blood/serum


  Specimens needed for creatinine clearance:
• improperly collected urine sample


  The greatest source of error in any clearance procedure utilizing urine is the use of ____________________
• mL/min

  GFR is reported in _________
• Urea clearance test


  - Replaced by creatinine clearance, inulin (Gold

  Standard), B2 microglobulin or radioisotopes

  
  

  - 40% of filtered urea is reabsorbed
• creatinine clearance test


  Recommended for measuring GFR because

  creatinine is normally found at relatively constant level in blood which provides the lab with an ENDOGENOUS procedure
• Inulin clearance test

  -A polymer of fructose

  - most accurate

  - Extremely stable substance that is not reabsorbed nor secreted by the tubules

  - must be infused at a constant rate throughout the testing period

  - EXOGENOUS
• Radioisotopes

  injection of radionucleotides not only determines GFR but also enables visualization of filtration in one or both kidneys
• beta2-microglobulin


  Distinguishes renal disease whether its glomerular or tubular
• Glomerular filtration Tests (5)

  Clearance Test:

  1. Urea

  2. Creatinine

  3. B-microglobulin

  4. Cyctine c

  5. Radioisotopes
• 87-107 mL/min


  FEMALE normal value for CREATININE CLEARANCE
• 107-139 mL/min

  Normal creatinine clearance for males
• 0.5-1.5 mg/dL

  Plasma creatinine
• Loss of tubular reabsorption capability

  is the 1st function affected by renal disease
• Concentration Test


  Test that measures the ability of the tubules to reabsorb water and salts
• Tubular function


  responsible in concentrating urine
• concentrated urine


  Water deprivation
• Diluted urine


  Water excess
• Tubular Reabsorption/Concentration Tests

  A. Fishberg Concentration Test and Mosenthal Concentration Tests

  B. Specific gravity

  C. Osmolarity
• Fishberg Concentration Test and Mosenthal Concentration Tests

  EARLIER METHODS of CONCENTRATION/REABSORPTION TESTS
• Fishberg test


  Px were deprived of fluids for 24hrs before measuring SG
• Mosenthal concentration test


  Compares the volume and SG of a day and night urine specimen.
• 1.025 SG


  A normal person deprived of water for 16 hrs has a SG of?
• Specific gravity


  most commonly used; measured using urinometer, refractometer or urine reagent strip;
• Specific gravity


  Test concerned both on the NUMBER and the WEIGHT of particles in urine specimen
• Osmolarity


  more sensitive since is only affected by the NUMBER of PARTICLES ,
• Osmolarity


  can be measured directly using osmometers that measure colligative properties.
• 275-300 mOsm


  Normal urine osmolality: ____________
• 3:1

  Urine to serum osmolality ratio:
• Types of osmometers


  1. Freezing point

  2. Vapor pressure
• Freezing point osmometer


  - Measures the freezing point of a sample to approx. -27 degrees Celsius.

  - The supercooled solution is vibrated to facilitate crystallization

  - Produces heat that would raise the tempt. To the solutions real freezing point.
• freezing point osmometer


  Supercooled > vibrate> crystallization
• Vapor pressure osmometers

  -Measures DEW point

  
  

  - Samples are absorbed into small filter paper disks

  with temperature sensitive thermocoupler.
• dew point temperature


  Temperature at which water vapor condenses to

  a liquid state.
• Osmolar clearance


  indicates how much water must be cleared each minute to produce a urine with the same osmolarity as the plasma

  
  

  -ability of kidney to respond to hydration
• FREE WATER CLEARANCE


  Determined by first calculating the osmolar clearance and subtracting the osmolar clearance value from the urine volume in mL/min.
• TUBULAR SECRETION AND RENAL BLOOD FLOW TEST

  1. PHENOLSULFONPTHALEIN (PSP)

  2.P-AMINOHIPPURIC ACID TEST (PAH)

  3. TITRATABLE ACIDITY
• PHENOLSULFONPTHALEIN (PSP)


  Test commonly associated with tubular secretion and renal blood flow at present