1. KIDNEY FUNCTION TEST
DR.RITTU CHANDEL
M.D. BIOCHEMISTRY (2ND YEAR)
GRANT GOVT MEDICAL COLLEGE, MUMBAI
21-08-2013

2. ANATOMY

3. PHYSIOLOGY

4. Glomerular filtration

5. GFR (120 – 130 ml/min/1.73 m2
• Rate of filtration affected by –
state of blood vessels
concentration of plasma proteins
Volume of glomerular filtrate depends on –
number of functioning glomeruli
effective glomerular filtration pressure
Volume reduced in extra renal conditions

6. Tubular function
• Tubular epithelial cells are highly specialized tissue –
able to reabsorb selectively some substances and
secrete others
• 170 l -------filtered
• 1.5 l --------excreted
• Nearly 99 % reabsorbed
• Renal threshold – plasma level above which
compound is excreted in urine
substance
Threshold value
glucose
180 mg/dl
lactate
60 mg/dl
bicarbonate
28 mEq/l
calcium
10 mg/dl

7. FUNCTIONS
1. Maintenance of homeostasis
2. Excretion of metabolic waste products
3. Retention of substance vital to body
4. Hormonal function
a.Erythropoietin
b.Calcitriol
c.renin

8. Preliminary investigation
• History – oliguria, polyuria, nocturia, ratio of
frequency of urination in day time and night time,
appearance of oedema
• Physical examination
• Urine analysis
• Biochemical parameters – increase in three
nitrogenous constituents of blood
( uric acid, urea, creatinine )
others

9. Renal function tests
1.
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2.
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3.
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4.
On glomerular filtration
Urea clearance test
Endogenous creatinine clearance test
Inulin clearance test
Cr51 - EDTA clearance test
Tests on glomerular permeability
Measure renal plasma flow
PAH test
Filtration fraction
Tubular function
Concentration and dilution tests
15 min – PSP excretion test
Miscellaneous test

10. clearance
• Substance S -----stable concentration in plasma
• Physiologically inert, freely filtered at glomerulus,
neither secreted, reabsorbed, non toxic, not
affected by dietary intake
• Amount of S entering kidney = amount of S
leaving it
• Filtered S = excreted S
s
• GFR x Ps = Us x V
• GFR = Us x V
•
Ps

11. Clearance
• Volume of blood or plasma which contains the
amount of substance which is excreted in the
urine in 1 min
Clearance = U X V
P
U ---- concentration of substance in urine
V----- volume of urine ( ml/minute)
P-----concentration of substance in plasma

13. substance
filtered
reabsorbed
secreted
Amount
excreted
/minute in
relation to
amount filtered
Glucose
Yes
Yes, completely
( 180 gm/dl)
TmG = 350
mg/mt
No
Not excreted
normally
Urea
yes
yes
no
less
Creatinine
Yes
no
no
Very close
PAH, phenol
red, diodrast
Yes
No
Yes
More than that
filtered
Inulin, mannitol, yes
thiosulphate
No
no
GFR =
clearance

14. UREA clearance tests
• Maximum clearance
( urine volume > or = 2 ml/min)
Clearance = U X V
P
= 1000 x 2.1
28
= 75 ml/ min
Standard clearance
(urine volume < 2ml /min)
Clearance = U X √v
P
= 54 ml/ min

15. Expression of result as % = result of clearance is
expressed as % of normal maximum or normal
standard urea clearance depending on urinary
output
Relation with body surface area
Cm x 1.73
BS
Cs x √1.73
BS

16. • Procedure
Break fast
1
hr
Empt
y
bladd
er
Urine
and
blood
collec
tion
1
hr
Urine
collection
Interpretation :
Urea clearance ≥ 70% ----------average normal function
40 – 70 % ------mild impairment
≤ 20 % ----------severe impairment
lunch

17. disease
Urea clearance
Chronic nephritis
Falls progressively
Reaches value half or less of normal before blood urea
concentration begins to rise
Terminal uremia
About 5 % of normal
Nephrotic syndrome
Normal until onset of renal insufficiency
Benign hypertension
Normal clearance usually maintained indefinitely

18. Blood urea
• Normal – 20 – 40 mg/dl
• Serum concentration increases as age advances
Increase in blood urea
Pre - renal
renal
Post renal
drugs
Dehydration
Severe vomiting
Intestinal
obstruction
Diarrhea
Diabetic coma
Severe burns
Fever
Severe infections
Acute
glomerulonephritis
Nephrosis
Malignant
hypertension
Chronic
pyelonephritis
Stones in urinary
tract
Enlarged prostate
Tumors of bladder
ACEI
Acetaminophen
Aminoglycosides
Amphotericin B
Diuretics
NSAIDS
Decreased blood urea – late pregnancy, starvation, hepatic failure

19. Creatinine clearance test
• 113 Da
• Produced by muscle from creatine and creatine
phosphate through non enzymatic dehydration
process
• 24 hr excretion of endogenous creatinine
Ccr = U X V
P
Normal – 95 – 105 ml/min

20. • procedure
500 ml water given
advantages
disadvantages
After 30 mins,
bladder emptied
and urine discarded
After 60 mins, urine
and blood sample
collected
• 1.Value close to GFR
• 2.Long term monitoring
• 1.Mild renal impairment ( creatinine blind
area )
• 2.Moderate impairment (secretion
component )
• 3.Severe impairment (extra renal excretion)

21. Estimated GFR ( eGFR)
• Cockcroft - Gault equation
Ccr
= (140 – age in yrs) x wt(kg) (0.85 in females) x Pcr
72
MDRD ( modification of diet in renal disease)
eGFR =
186 x {creatinine} - 1.154 ( age ) – 0.203 x 0.742
88.4

22. Serum creatinine
Normal = 0.7 – 1.5 mg/dl
decrease
increase
Low muscle mass
Females
Malnutrition
Thiazides
vancomycin
Old age
Males
Glomerulonephritis
Pyelonephritis
Renal failure
Urinary obstruction
CCF, dehydration, shock
Amphotericin B
Captopril
Cephalosporin
kanamycin

23. Inulin clearance test
• Ideal substance
• Procedure:
Overnight fast
Light breakfast
at 7:30 am
10 gm inulin in
100 ml saline
inj i.v. at 10
ml/min at 8am
Bladder
emptied at
9am, urine
discarded
After 30 mins,
urine and
blood
collected
After 60 mins,
urine and
blood
collected
Normal = 125 ml/min
range = 100 – 150 ml/min
Inulin clearance x 0.6 = maximum urea clearance

24. Cystatin C
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122 amino acids, 13000 Da
Inhibitor of cysteine proteinase
Produced by all nucleated cells
Production rate constant
Not affected by muscle mass, sex, race
High isoelectric point, which enable it to be more
freely filtered
• Sensitive changes in creatinine blind area
• Extremely sensitive to minor changes in GFR
• Measurment expensive and difficult

25. Substances used in clearance tests
Endogenous substance – urea, creatinine, cystatin C, β – trace
proteins, β - 2 – microglobulin, tryptophan
glycoconjugate
β - 2 – microglobulin
Polypeptide, 11.6 kDa, 99 amino acid
Component of MHC -1
In all nucleated cells
Needed for production of CD-8
tryptophan glycoconjugate
Mannopyranosyl – l – tryptophan (MPT) – produced in body by
glycoconjugation of tryptophan
Measured by HPLC

26. Clearance tests
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Gold standard – inulin ( sinistrin)
Silver standard – Cr51 - EDTA
Tc99 - DTPA
I125 – iothalamate
iohexol
Bronze standard – creatinine
cystatin C
Uncertain clinical use – creatinine clearance
urea
retinol binding protein
α1 - microglobulin

27. Grading of chronic kidney disease
state
grade
GFR ml/min/1.73sq m
Minimal damage
1
>90
Mild damage
2
60 – 89
Moderate damage
3
30 – 59
Severe damage
4
15 – 29
End stage
5
< 15
CKD = GFR < 60 ml/min/1.73 m2 for 3 months or more with or
without kidney damage

28. Test for glomerular permeability
• First sign of glomerular injury (before decrease
in GFR)
• Proteinuria
• Normal protein excretion = <150 mg/24 hrs
Glomerular damge
• Glomerular
proteinuria
Others
Nephron loss proteinuria
Urogenic protreinuria
Increase in low mol.
Wt proteins
• Overflow
proteinuria
Decrease in
reabsorptive capacity
• Tubular proteinuria

29. • Glomerular proteinuria
Albuminuria ( early morning urine sample
prefered)
300 mg/day
Benign proteinuria
300 – 1000 mg/day
Pathological proteinuria
>1000 mg/day
Glomerular proteinuria
Large quantity of albumin
nephrosis
Small quantity of albumin
Acute nephritis, pregnancy
Measurment of albuminuria is helpful in monitoring kidney function and response to
therapy in many forms of CKD

30. • Microalbuminuria/ minimal albuminuria/pauci albuminuria
30 – 300 mg/day in urine
Earliest sign of renal damage – diabetes mellitus, hypertension
Overflow proteinuria
Hemoglobinuria (hemolytic anemia)
Myoglobinuria ( crush injury)
Multiple myeloma
Hematuria –confirms glomerular damage, also earliest sign
before decrease in GFR

31. Tubular proteinuria
Functional nephrons decrease, GFR
decreases
Remaining nephrons are overworked
Tubular reabsorption impaired
Low molecular wt. protein appear in
urine
Hence can be used as markers of tubular
damage
Eg. Β – d –glucosaminidase, lysozyme

32. Test for renal blood flow
1. Measurment of renal plasma flow
PAH - filtered and secreted
- removed completely during a single
circulation of blood through the kidneys
RPF = 574 ml/min

33. 2. Filtration fraction:
Fraction of plasma passing through the kidney
FF = Cin
= GFR = 125 = 0.217 ( 21.7%)
CPAH
RPF
594
Normal range = 0.16 – 0.21
disease
Filtration fraction
Essential
hypertension
Normal in early period, as disease
progresses ↓ RPF > ↓ GFR -------FF ↑
Malignant phase of
hypertension
↑↑↑↑ FF
glomerulonephritis
Greater ↓ in GFR than RPF, ↓FF

34. Pathophysiology of tubular function
Alteration
in Tubular
function
ischemia
Toxic
substances
Impairing
transfer of
substances
across
tubular cells

35. Concentration and dilution tests
• Ability to concentrate and dilute urine
dependent on:
GFR
RPF
Tubular mass
Healthy tubular cells
Presence of ADH

36. •
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Concentration tests/fluid deprivation
tests
ability of kidney to concentrate urine
measurement of specific gravity of urine
Simple, bedside procedure
Most sensitive means of detecting early impairment in renal
function
1. Fishberg concentration test –
Procedure:
Meal at 7 pm------no fluid from 8 pm to 10 am
Urine specimen collected at 8, 9, 10 am
Determine specific gravity
Result:
Specific gravity of any one specimen > 1.025----NORMAL
< or = 1.020 ---impaired
fixed at 1.010 ----severe

37. 2. Lashmet and newburg concentration test
Severe fluid intake restriction over a period of 38
hrs
3.With posterior pitutary extract
s.c. inj of 10 pressor units of posterior pitutary
extract (0.5 ml of vasopressin inj)
Result –
specific gravity - > or = 1.020 -----normal
Failure to concentrate -----renal damage
Advantages – CCF, DI

38. Water dilution or elimination test
• Ability of kidney to eliminate water is tested
by measuring urinary output after ingesting
large volume of water
Patient in supine position
Evening meal
at 8 pm
After 12 hrs
i.e. 8 am first
urine sample
discarded
After 8 am ,
1200 ml given
in half hr
Bladder
emptied at 9,
10, 11 ,12
Kidney function
Urine voided in 4 hrs
Specific gravity of at least 1
specimen
normal
>1000 ml (80%)
Larger part excreted in first 2 hrs)
< or = 1.003
impaired
<1000 ml (80%)
Doesn’t fall to 1.003
Fixed at 1.010 in severe
renal damage

39. Test of tubular excretion and
reabsorption
• Phenol sulphthalein (PSP) excretion test
94%----excreted, 6%----glomerular filtration
15 min PSP Test - reliable and sensitive
Test 1 ml
( 6 mg)
inj iv
30 -50 %
excreted in
1st 15 mins
<23%
excreted in
1st 15 mins

40. Miscellaneous tests
• Test of renal ability to excrete acid
Give NH4Cl in
gelatin coated
capsule (0.1
mg/kg)
Collect all
urine samples
in next 6 hrs.
measure pH
and NH3
content
Empty bladder
1 hr later,
urine
discarded
Kidney function
pH
NH3
normal
5.3
30 -90 mEq/min
Renal failure
decreases
decreases
Renal tubular
acidosis
5.7 - 7
decreases
Contraindications
: liver disease, acidosis

41. • IVP
• Radioactive scanning
• Renal biopsy
• Immunological tests
1. Anti GBM antibodies
2. ANCA
3. Pattern of complement in nephritis

42. GLOMERULAR DYSFUNCTION
TUBULAR DYSFUNCTION
Increase in Se urea
Urinary concentration decreases
Increase in Se creatinine
Dilution tests abnormal
Inulin clearance decreases
Uric acid excretion decreases
Creatinine clearance decreases
Blood uric acid increases
Urea clearance decreases
Acidification of urine decreases
Urine volume decreases
Aminoaciduria present
Specific gravity increases
Urine volume increases
Se phosphate increases
Specific gravity decreases
Poteinuria present
Se phosphate decreases

43. bibliography
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Satyanaryan
Ranna shinde
Vasudevan
Kaplan
Teitz
Varley
Pankaja naik
THANK YOU