Renal function evaluation is required for the following: Detection of renal damage Assessment of the extent of renal damage Monitoring the progression of renal disease Monitoring and adjusting the dose of potentially renal toxic drugs excreted by kidney.

2.  Filtration of blood and preparation of
ultrafiltrate fluid as urine.
 Reabsorption of useful substances such
as glucose,amino acids, electrolytes,
etc.
 Homeostasis of the extracellular volume.
 Maintenance of the acid base status,
water and electrolytes
 Endocrine functions and activation of
hormones such as synthesis of
erythropoietin, activation of vitamin D,
etc.

3. ROUTINE
LABORATORY
TEST
•URINE
• VOLUME
• Ph
• Normal
constituen
ts
• Abnormal
constituen
ts
•Blood
• Urea
• creatinine
• Ph, Gases
&
Electrolyte
TEST
FOR
GLOMERULAR
FUNCTIONS
• Renal
Clearance test
• Insulin
clearance
• Urea
clearance
• Creatinine
clearance
• Renal plasma
flow
TESTS
FOR
TUBULAR
FUNCTIONS
• Urine
concentration
test
• Urine dilution
test
• Urine
acidification
test

4. Renal function evaluation is required for
the following:
 Detection of renal damage
 Assessment of the extent of renal
damage
 Monitoring the progression of renal
disease
 Monitoring and adjusting the dose of
potentially renal toxic drugs excreted
by kidney.

5.  Routine urine examination is usually
the first test undertaken to assess
renal function and very often it gives
some important information like
proteinuria to warrant further renal
investigations.
 The common tests include the
measurement of urea and creatinine
in blood and their clearance rate by
kidneys.

6.  Urea is the end product of amino acid
catabolism, synthesized in liver and is
excreted by kidneys.
 It is freely filtered by the glomerulus
and 40-70% of it is passively absorbed
by diffusion into the renal tubules.
 This diffusion is dependent upon urine
flow rate. When the urinary flow is
slow the diffusion is more. It also
increases following high dietary
protein intake.

7.  Normal plasma urea level is 15-
40mg/dL and daily urinary urea
excretion is 2 gm% or 20-40 gm/day.
 It is not a very good test due to its
dependence on urinary flow rate, and
influence of non-renal conditions like
dehydration, dietary protein intake,
cardiac failure, liver diseases, etc.
 Still, it is the most commonly used
renal function test for initial
screening.

8.  Sometimes blood urea is represented
as its nitrogen content i.e. as blood
urea nitrogen (BUN).
 It is roughly 50% of the urea level
since one molecule of urea (mol. wt. =
60) contains two nitrogen atoms (28).
Hence the ratio of nitrogen (BUN) in
urea is = 28/60=0.47 = 47%

9.  Creatinine is a waste product derived
from creatine and is freely filtered in the
kidney but is not absorbed. It is not
dependent on dietary protein intake but
on muscle mass. On a day-to day basis
without muscle disease, it is a good
renal function test.
 Normal plasma creatinine level is 0.8-1.2
mg/dL and daily urinary excretion is 1-2
gm.
 A significant rise in plasma creatinine
indicates 50% renal damage. The rise
correlates with the decrease in GFR over
a range of 75%-25%

10.  Clearance is a measure of GFR. Under ideal
conditions, it is equal to GFR.
 Creatinine clearance gives a good estimate
of GFR at low plasma creatinine level. But
20-30% or more GFR values are seen at high
creatinine level.
 Clearance of urea is influenced by urinary
flow rate and hence should not be carried
out when urine output is reduced greatly.
 But overall creatinine clearance is better
than urea clearance with normal value of
85-130mL/ minute. Reduced values indicate
renal damage and decrease in glomerular
filtration.

11.  Proteinuria is the first sign of glomerular
injury before any decrease in GFR.
 Excretion of > 150 mg/day of total
urinary protein or of albumin > 30 mg per
day is indicative of glomerular damage.
 Microalbuminuria (albumin excretion 30-
300 mg/day) is the earliest sign of renal
damage due to microvascular glomerular
damage as seen in diabetes mellitus and
hypertension.

12.  In minimal glomerular damage, low
molecular weight proteins such as
albumin, a-antitrypsin and transferrin
are excreted into the urine (selective
proteinuria). This can be detected by
electrophoresis.

13.  Impaired tubular function also leads
to a decrease in the renal tubular
capacity to conserve sodium as per
the body requirement, and so Na*
excretion increases.

14. BIOLOGICAL
PARAMETER
NORMAL VALUE
 Blood Urea
 Serum creatinine
 pH
 pCO2
 HCO3-
 Na+
 K+
 15-40mg/dL
 0.8- 1.3mg/dL
 7.35-7.45
 35-45mm Hg
 22-26 m Eq/L
 136-145mEq/L
 3.5-5.0mEq/L