8. GLOMERULAR FILTRATION
700ml of plasma passes through kidneys per
minute.
From this 120 to125 ml is filtered
per/minute by kidneys.
THIS IS GFR.
9. GFR DECREASES
GFR DECREASES IN
1. OCCLUSION OF AFFERENT
ARTERIOLES
2. DECREASED PERMEABILITY
OF THE MEMBRANE.
3. INCREASED INTRA
CAPSULAR PRESSURE
10. GFR INCREASES IN
1. INCRESED BP
2. DECREASED BLOOD PROTEIN
OSMATIC PRESSURE
3. INCRESED GLOMERULAR
PERMEABILITY
11. Effective filtration pressure
• Is the result of
A)The glomerular pressure in
glomerular capillaries
B)The opposing osmotic pressure of
plasma proteins&Hydrostatic pressure of
Bowmens capsule fluid
• Capillary pressure=75 mmHg
• Osmatic pressure of plasmproteins=30mmHg
12. Net effective filtration pressure
• Pef=Pg-(Ppp+Pbc) = 75-(30+20)
• Pef=25mmHg
• Pg=hydrostatic pressure in the glomerular
capillaries
• Ppp=osmotic pressure of plasma proteins
• Pbc=hydrostatic pressure of the bowmans
capsule fluid
13. RATE OF FILTRATION IS INFLUENCED BY
• Variation in BP in glomerular cappilary
• Concentration of plasma proteins
• Factors altering intratubular pressure viz.
a) rise with ureteral obstruction
b) during osmotic diuresis
c) state of blood vessels
14. THE VOLUME OF GLOMERULAR
FILTRATE FORMED DEPENDS ON:
• The number of glomeruli functioning at a time,
• The volume of blood passing through the
glomeruli per minute and
• The effective glomerular filtration pressure
• In normal circumastances 700ml of plasma flow
through the kidneys per minute& 120 to125ml of
fluid is filtered in to bowmans capsule
15. Volume of filtrate reduced in extra
renal conditions
• 1.Dehydartion
• 2.Oligemic shock
• 3.Cardiac failure
• 4.lower the glomerular filtration pressure
16. • TUBULAR REABSORPTION
Formation of primary urine is 120 to 125 ml/mt.
• Only 1 to 2ml/mt reaches the bldder,
• 170 litres of water filtered through the glomeruli
&only 1.5 litre is excreted in the urine. So,99%
glomerular filtrate is reabsorbed in the tubules
• TUBULAR SECRETION
• Examples of substances secreted by the tubular
epithelium are creatinine&potassium
17. RENAL FUNCTION TESTS
1.TEST BASED ON GLOMERULAR FILTRATION:
• Urea clearance test
• Endogenous creatinine clearance test
• Inulin clearance test
• Cr51-EDTA clearance test
18. 2.TESTS TO MEASURE RENAL PLASM FLOW
• Para-amino hippurate test(PAH)
• Filtration fraction
3.TESTS BASED ON TUBULAR FUNCTION:
--Concentration and Dilution tests
--15 minute-PSP excretion test
--Measurement of tubular secretory mass
MISCELANEOUS TESTS; Can determine
size, shape, any
Tumour, obstuction, Infarct etc.
19. CLEARANCE TESTS
• CLEARANCE;DEFINED AS A VOLUME OF
BLOOD OR PLASMA WHICH CONTAINS
THEAMOUNT OF THE SUBSTANCE WHICH IS
EXCRETED IN THE URINE OR
• THE CLEARANCE OF SUBSTANCE MAY BE
DEFINED AS THE VOLUME OF BLOOD OR
PLASMA CLEARED OF THE SUBSTANCE FOUND
IN ONE MINUTE EXCRETION OF URINE
20. SALIENT FEATURES OF SUBSTANCE USED FOR
CLEARANCE TESTS
a) It must be non toxic
b) It should be small enough to pass through
the glomerular membrane
c) It should neither be secreted nor be
absorbed by renal tubules
d) It should not be metabolised in the body
21. CREATININE CLEARANCE
• CREATININE CLEARANCE: Useful in the diagnosis and
prognosis of the kidney disease.
• CREATININE CLEARANCE=
Urine creatinine in mg/dl x Total volume of urine
___________________________________
Serum creatinine in mg/dl x 1440
REF.RANGE: Male:125ml/mt
Female:115ml/mt
A decresed creatinine clearance is very sensitive indicator of a
reduced glomerular filtration rate, due to acute or chronic
damage.
22. CREATININE
• The kidney reserve is such that only when about 50%
kidney function must be lost before creatinine level
in blood is raised.
• But serum creatinine minor change in concentration
may be of significance, and the serum level usually
parallel to the severity of the disease.
23. CREATININE
• CREATININE:REF.RANGE:800---2000mg/day.
• Creatinine is a waste product formed from
Creatinine phosphate which is stored form of the energy in
muscle. this conversion is spontaneous, non enzymatic
process and is dependant on total muscle mass and this mass
is not affected by diet,age,sex or exercise.
• Since the production is continuous and it is not affected by
other factors that’s why Creatinine is an ideal substance for
clearance test. This test is mainly to assess the glomerular
filtration. GFR provides the most useful index for the
assessment of the severity of renal disease.
24. 24 hour urine collection
A 24 hour urine collection is a simple diagnostic
procedure that measures the components of
urine. The test is cheap, sensitive and is used to
assess kidney function, hormones other
substances can also be estimated
25. RISKS OF THE PROCEDURE
• 24 hour urine collection is a safe, noninvasive procedure that
is usually done without direct assistance.
• Certain factors or conditions may interfere with the accuracy
of a 24 hour urine collection, include the following
• Forgetting to collect some of urine
• Going beyond 24 hour collection period and collecting excess
urine
• Losing urine from specimen container through spilling
• Not keeping urine cold during collection period
• Acute stress
• Vigorous exercise
26. PATIENT EDUCATION:
• The accuracy of the test results depends on the
accuracy of the specimen collection
• Collect in a clean environment
• It is important that dust from clothing not contribute
to the specimen content
• Do not collect urine in metal glass containers
• Females: Do not collect urine while menstruating
27. PATIENT INSTRUCTIONS
• CAUTION: The collection bottle may contain a
preservative in the form of tablets or strong acid
solution which may burn your skin.
• Do not remove preservative from the bottle
• Keep the bottle upright so it does not spill
• Do not urinate directly in to the bottle
• Keep out of reach of children
• If liquid in the bottle is spilled or splashed, wash
immediately.
28. PATIENT INSTRUCTIONS
• Record the time and date on the collection container
label as the START TIME AND DATE. Also record the
time and date in the FINISH TIME/DATE--------space
provided on the laboratory requisition
• Deliver the container and lab requisition to the
laboratory immediately the collection is finished.
29. PRESERVATIVES
• Preservatives to be added to 24 hour urine collection
for various biochemical estimation
• Amylase, sodium, potassium and chloride--------------
no preservative
• C peptide, cortisol, lead and zinc-------------------------
no preservative
• Protein and citrate------- no preservative
• Uric acid--------- no preservative
31. CREATININE CLEARANCE
• This is covenient method &sensitive indicator for GFR
• ADVANTAGE OF CREATININE CLEARANCE;
– A)It is a normal metabolite of the body
– B)It does not require I.V. administration
– C)Estimation of creatinine is simple
– D)In early stages it has got advantage over S.Creatinine
• CR.CLEARANCE=UV/P
• In the calculation surface area is important
• Body surface area is calculated from
• LogA=0.425 LogW+0.725 LogH -2.144
32. CREATININE CLEARANCE
• This is covenient method &sensitive indicator for GFR
• ADVANTAGE OF CREATININE CLEARANCE;
– A)It is a normal metabolite of the body
– B)It does not require I.V. administration
– C)Estimation of creatinine is simple
– D)In early stages it has got advantage over S.Creatinine
• CR.CLEARANCE=UV/P
• In the calculation surface area is important
• Body surface area is calculated from
33. LogA=0.425 Log SW+0.725 log H-2.144
A=Body surface area in meter square
W=Weight in Kg H=Height in cm
• Standard body surface area is 1.73 m²
• Creatinine clearance corrected for body
surface area
Calculated as
UxV x 1.73/PxA
Male normal value=125 ml/mt
Female normal value=115 ml/mt
34. A rough estimate of Creatinine clearance
in Males=(140-Age) x Wt in Kg/72 xPcr
• C cr in Females=0.85 xCcr
• CREATININE COEFFICIENT=URINARY CREATININE
EXPRESSED IN mg/kg body weight
Normal range in Males 20 to 28mg/kg
Females 15 to 21mg/kg
Factor for converting mg/kg/ to nmol/kg/=0.00884
Value increses in Muscular Dystrophy
35. P/C RATIO
• Creatinine estimation is also useful in the muscular
dystrophy and in Nephrotic syndrome.
• P/C RATIO=protein concentration in mg/dl
___________________________________
creatinine concentration in mg/dl
p/c ratio ref.range=< 1
P/C ratio increases in NEPHROTIC SYNDROME
36. M/C RATIO
• MC RATIO=mg of micro albumin/gms of
creatinine
• AS PER AMERICAN DIABETIC ASSOCIATION
• NORMAL VALUE IS LESS THAN 30 mg of
uma/gm creatinine
• Abnormal 30 to 299 Microalbuminemia
• More than 300 Maacroalbuminemia
37. INULIN CLEARANCE
• 10 gm of Inulin is dissolved in 100ml of saline is
injected I.V at a rate of 1 ml/mt over 2 hours
I.C=UV/P ml/mt
• U=concentration of inulin in urine in mg/dl
• V=volume(ml) of urine passed /mt
• P=concentration of inulin in plasma in mg/dl
• I.C=125ml i.e GFR=125ml
• Similar clearance value is seen with
MANNITOL,SORBITOL&DULCITOL
38. INULIN CLEARENCE DECRESES IN
• Decrease in renal flow
• Obliteration or decrese in number of functioning glomeruli
• Defect in the effective glomerular filtration pressure
• Used to know the substance reabsorbed
• Urea reabsorbed in tubules=I.C-UREA CLEARANCE
• -----------------------------
• I.C
125-75
• -------=0.4 SO,40% OF UREA REABSORBED
125
39. UREA CLEARANCE
• Maximum clearance; If the urine volume exceeds
2 ml/mt.
• Volume of blood cleared of urea/mt=UV/P =1000
X 2.1/28=75
• Standered clearance;when the urinary volume is
less than 2ml/mt
• Cs=Ux square root of √V/P=54 ml
• Only 60% of glomelular filtrate urea excreted
• Urea clearance is 60% of Inulin clearance
=UC/0.6=I.C
40. Determination of CR₅₁ EDTA
CLEARANCE
• SINGLE INJECTION IS USED FOR GFR
ESTIMATION
• USED FOR CHILDREN &ADULTS
• CONVENIENT FOR CHILDREN WHERE IT IS
NOT EASY TO COLLECT 24 HOUR URINE.
