Biochemistry Kidney Function Test-lecture 3 for B.pharm, Pharm D

2. Kidney function tests divided into 4 groups-
 Glomerular function tests:
All the clearance tests (insulin, creatinine ,urea) are included in
this groups.
 Tubular function tests:
Urine concentration or dilution test, urine acidification test.
 Analysis of blood/serum:
Estimation of blood urea, serum creatinine , protein &
electrolyte are useful to assess renal function.
 Urine examination:
This includes examination of urine volume, pH, specific
gravity, abnormal constituent etc.

3. Clearance tests
Clearance is defined as the volume of plasma that would be
completely cleared of a substances per minute
The max. Rate at which the plasma can be cleared of any substance is
equal to GFR

4. Urine concentration tests
•This is a test to assess the renal tubular
function.
•It is a simple test and involve accurate
measurement of gravity which depends on the
concentration of solute in urine.
•A specific gravity of 1.020 in the early morning
urine sample is considered to be normal.
 Tubular function tests:
Urine concentration or dilution test, urine acidification test.

5. Osmolality and specific gravity
•The osmolality of urine is variable.
•In normal individuals, it may range from 500-1200
milliosmole/kg.
•The plasma osmolality is around 300 milliosmoles/kg.
•The normal ratio of osmolality between urine &
plasma is around 2-4.
…cont

6. •It is found that the urine (without any protein
or high molecular weight substance) with an
osmolality of 800 mosm/kg has a specific
gravity of 1.020
•Therefore, measurement of urine osmolality
will also help to assess tubular function.

7. Blood urea estimation
Blood urea estimation is widely used as a screnning test for
the evaluation of kidney function.
It is estimated in laboratory by urease enzyme or diacetyl
monoxine.
Analysis of blood/serum:
Estimation of blood urea, serum creatinine , protein & electrolyte are useful to
assess renal function.

8. Elevation in blood urea can be
due to:
Pre-renal: associated with increase protein breakdown
leading to negative nitrogen balance observed after
surgery, prolonged fever, diabetic comma etc.
Renal: in renal disorder like chronic nephrites etc blood
urea is increased.
Post renal: whenever their is an obstruction in the
urinary track blood urea is elevated. This is due to
increased reabsorption of urea by renal tubules.