2. Functions of the kidney
ī§ Regulation of water, electrolyte
and acidâbase balance
ī§ Excretion metabolic waste eg.
urea, creatinine, UA, urobilinogen,
PO4
-, SO4
-, oxalic acid etc.
ī§ Formation of renin, erythropoietin
and calcitriol
2
3. Indications of testing
ī§ Diagnosis of renal disease
ī§ Assessment of severity and
prognosis of renal disease
ī§ Differential diagnosis of edema and
proteinuria
ī§ Differential diagnosis electrolyte
abnormalities
ī§ Differential diagnosis of acid base
disorders
3
4. Tests
ī§ Routine & bacteriological
examination of urine
(Urine RME and urine C/S)
ī§ Blood biochemistry
ī§ Glomerular function tests
ī§ Tubular function tests
4
6. Urine RME and urine C/S
ī§ Physical examination of urine
ī§ Chemical examination of urine
ī§ Microscopic examination of urine
ī§ Bacteriological examination of
urine
6
8. Collection of urine
ī§ Random...anytime
eg. spot urinary ACR
ī§ Timed...at particular time
eg. during OGTT
ī§ 24 hrs...whole urine of last 24 hour (8am â 8am
next morning)
eg. 24hrs UTP, 24hrs urinary electrolyte, CCR
8
9. 24hrs urine collection
ī§ The bladder should be emptied at the beginning
of collection and urine discarded (If starting time
is 8 am; voided urine of 8 am has to be
discarded).
ī§ Fecal contamination should be avoided. Urine
should be collected before the act of defecation.
9
10. 24hrs urine collection contd.
ī§ Voided urine should be collected in a separate
container and then added to the main container
containing acid preservatives to avoid splashing.
ī§ Starting time has to be noted in the main
container and stored at ~4°C.
ī§ All subsequent voiding of 24hrs is collected
including that of 8 am next morning. No portion
should be discarded.
10
11. Changes in urine on long time storage
ī§ Bacterial contamination
ī§ Chemical decomposition of analyte
Bacterial fermentation of glucose
Conversion of urea to NH4
+
ī§ Precipitation of analytes â
PO4
- precipitates
ī§ Oxidation of unstable components â
Urobilinogen is oxidized to urobillin
11
14. Physical examination
Characteristics Normal Abnormalities with cause
Volume* 500 â 2500ml/day Polyuria...in DM & DI
Oligouria...in RF, UT
obstruction, dehydration etc.
Colour Straw â slight hazy Dark yellow...in jaundice
Red...in hematuria
Appearance Clear Turbid...in UTI
Osmolarity 600 â 900mosm/L â...DM, dehydration
â...DI
Specific gravity 1.010 â 1.040
*requires 24hrs urine
14
15. Chemical examination
Characteristics Normal Abnormal constituents
pH 4.5 â 8.0 (â6.0)
Protein Nil or trace (<150mg/day) Excess protein
Inorganic Na+, K+, Cl-, Ca2+, Mg2+,
PO4
-
Any electrolyte in excess
Organic NH4
+, urea, UA,
creatinine, urobilinogen
Sugar/ glucose, ketone
bodies, blood, bilirubin/
bile pigment, bile salts,
excess urobilinogen
15
16. Detection of abnormal constituent
Constituent Test Cause of presence
Sugar/ Glucose Benedictâs test DM, renal glycosuria
Protein Heat coagulation test Proteinuria due to any cause
Ketone bodies Rotheraâs test DKA
Blood Benzidine test Hemolytic disease
Bilirubin/ Bile
pigment
Fouchetâs test Obstructive jaundice
Bile salts Hayâs sulfur test Obstructive jaundice
Urobilinogen Ehrlichâs test Hemolytic jaundice
16
25. Glomerular function tests
ī§ Renal clearance tests
a) Inulin clearance test (normal: 125ml/min)
b) Creatinine clearance test (normal: 70 â 140ml/min)
c) Urea clearance test (normal: 60 â 70ml/min)
ī§ Measurement of GFR through
īRadioisotope clearance study â 99mTc-DTPA, 51Cr-
EDTA
īFormula based estimated GFR (eGFR)*
ī§ Detection of albumin
25
26. Clearance tests
Based upon
C (ml/min) = U x V
P
C = Renal clearance of substance in ml/min
U = Concentration of substance in urine (mg%)
V = Volume of urine in ml excreted per min
P = Concentration of substance in plasma (mg%)
âEndogenousâ creatinine clearance test is preferred over
intravenously injected inulin clearance test
26
27. Formula based estimation of GFR (eGFR)
27
CockroftâGault equation
eGFR (mL/min/1.73/m2) = (140 â age) x weight (kg) x (constant)
Serum creatinine [Îŧmol/L]
Constant = 1.23 for male & 1.04 for female
Modification of diet in renal disease (MDRD) equation
eGFR (mL/min/1.73 m2) = 1.86 x (SCr)â1.154 x (age)â0.203 x constant (0.742 if female) x
(1.21 if black African)
To convert creatinine values in Îŧmol/L to mg/dL multiply by 0.0113
CKD-EPI equation
eGFR (mL/min/1.73 m2) = 141 x min(SCr/Îē, 1)Îą x max(SCr/Îē, 1)â1.209 x 0.993Age x 1.018 [if
female] x 1.159 [if black]
SCr is serum creatinine in mg/dL, Îē is 0.7 for female & 0.9 for male, Îą is â0.329
for female & â0.411 for male, min indicates minimum of SCr/Îē or 1 & max
indicates maximum of SCr/Îē or 1
31. Tubular function tests
ī§ Urine concentration and dilution test
ī Urine concentration test
a) Water deprivation test
b) Urine concentration test with ADH
ī Urine dilution test (excess water intake test)
ī§ Detection of LMW protein (Îą2 or β2 microglobulin)
31
32. Water deprivation test
ī§ Restriction of water/fluid for certain period (8 â
14hrs; with meal of <200ml fluid content)
supposed to excrete concentrated urine with
high osmolarity and specific gravity (âĨ1.025).
ī§ Failure to increase osmolarity and specific
gravity (remains â¤1.020) indicate tubular
damage or ADH deficiency.
32
33. Urine concentration test with ADH
ī§ S/C injection of ADH following evening meal
followed by overnight fasting and measurement
of next morning 2 urine sample specific gravity
ī§ In normal kidney, at least one of two sample
specific gravity âĨ1.020
ī§ In tubular impairment, failure to concentrate
urine >1.020
33
36. Origin of urinary protein
Filtered
Albumin
Pre-albumin
β2-microglobulin
Ceruloplasmin
Haptoglobin
Transferrin
Tubular secretion or
desquamation
Tamm-Horsfall protein
36
37. Types
Macroproteinuria
âĸ24hrs UTP >300mg/day
âĸDipstick positive
âĸDetected by heat
coagulation test
Microproteinuria
âĸMainly albumin
âĸ24hrs UTP 30-
300mg/day
âĸDipstick negative
âĸNot detected by heat
coagulation test
eg. Early DN, HTN
37
38. Types of macroproteinuria
Functional
eg. PE
Physiological
eg. fever,
trauma, stress,
pregnancy, high
protein intake
Glomerular
eg. AGN, NS
Tubular
eg. ATN
Overflow
eg. multiple
myeloma
38
39. Dipstick testing
ī§ Strips impregnated with chemical
reagents
ī§ Urinalysis strip for quick
determination of urobilinogen,
bilirubin, ketone, creatinine, blood,
protein, microalbumin, nitrite,
leukocytes, glucose, specific
gravity, pH and ascorbic acid in
urine.
39
40. Dipstick testing
ī§ Strip is manually immersed in the
urine specimen
ī§ Reagents in each block react with
a specific component of urine
ī§ Block changes colour if the
component is present
ī§ Colour change proportional to
concentration of component being
tested for
40
42. Heat coagulation test
ī§ 2/3rd of test tube filled with urine
ī§ Heating of upper 1/3rd of tube
inclining at an angle by low flame
ī§ Turbidity develops in heated
portion of urine
ī§ 1-2 drops of 5% acetic acid is
added and reheated
ī§ Persistence of turbidity indicates
presence of protein
42
43. Need to keep in mind
ī§ Turbidity may appear due to protein or phosphate
ī§ After addition of 5% acetic acid turbidity due to
phosphate disappears but that due to protein
persists
43
44. Benedictâs test
ī§ 5ml of Benedictâs qualitative
solution taken in a test tube and
heated
ī§ 8 drops of urine is added and
reheated to boiling point followed
by cooling
ī§ Change of colour indicates
presence of reducing substance
44
45. Appearance Colour change Grade
Blue (No color change) Absent
Green Trace
Yellow Low
Orange Moderate
Brick red High
Benedictâs test: interpretation
45
46. Need to keep in mind
ī§ The test determines presence of reducing substance,
not glucose or sugar
ī§ Reducing sugar: All mono and disaccharides except
sucrose
ī§ Reducing substance: All reducing sugar,
homogentisic acid, nalidixic acid, uric acid, ascorbic
acid, aspirin etc.
46
47. Rotheraâs test
ī§ 5ml of urine taken in a test tube
followed by addition of ammonium
sulphate till saturation
ī§ Addition of 2 drops of 5% sodium
nitroprusside solution followed by
few drops of ammonia water
ī§ After mixing the content, tube is kept
for 5min
ī§ In presence of ketone body, a purple
colour ring appears
47
48. Need to keep in mind
ī§ Acetone is volatile, not present in urine
ī§ β-hydroxybutyrate does not give this test
positive
ī§ Only acetoacetate give Rotheraâs test positive
48