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8/21/2019 Physiological Basis of Evaluation Of RF
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Physiological basof evaluation of
renal function
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An Introduction to the Urinary System
Produce urine
Transports urine
Toward bladder
Temporarily store
urine
Conduct urine
to exterior
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The Function of Urinary System
Excretion & Elimination:
removal of organic wastes
products from body fluids (urea,creatinine, uric acid)
Homeostatic regulation:
Water -Salt Balance
Acid - base Balance
Endocrine function:
Hormones
A)
B)
C)
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Formation of urine
Urine is formed by the help of nephrons
About 1 million nephrons are present in one kidney
Nephron contains bowmens capsule, proximal convoluted tloop of Henle , distal convoluted tubule and collecting tubul
blood supply high-1200ml/min
120-125ml/min is filtered which is known as glomerular filtr(GFR)
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Urine formation
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Why Test Renal Function?
To identify renal dysfunction. To diagnose renal disease.
To monitor disease progress.
To monitor response to treatment.
To assess changes in function that may impact on th(e.g. Digoxin, chemotherapy).
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Renal function tests
Analysis of urine
Analysis of blood
Renal clearance test
Radiology and renal imaging
Renal biopsy
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ANALYSIS OF URINE
1)Volume2)Colour
3)Osmolality & sp. Gravity
4)PH
5)Abnormal urinary constituents
6)Microscopic examination
7)Bacteriological examination
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1)Volume
N 8002500 ml /day
Polyuriamore than 3 L / day
Oligurialess than 500 ml / day
Anuriano urine (less than 50 ml /day )
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2)Colour
Light yellow
Brownish yellowconj. Bilirubin
Cloudy appearancealkaline urine (ca phosphate ppt.)
Frothy appearanceproteinuria
Red-dark brown tinge - porphyria
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3)Osmolality & Sp. Gravity
50 mOsm / kg1200 mOsm / kg 1.0031.030
Method-
early morning urine sample > 600 mOsm/kg , > 1.018
Fixed osmolality 300 mOsm/kg,1.010 advance urinary failure
Persistent low osmolality ( less than 100 mOsm/kg) even afte
of water deprivation - DI
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4)PH
4.58.0 (slightly acidic)
Infection with urea spitting bacteriaImpairment of tubular acidification
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5)Abnormal urinary constituents
1) Proteinuria > 150 mg/day
Mild transient proteinuriacongestive heart failure
Orthostatic proteinuria
Glomerular proteinuria( permeability)nephrotic syndrome , a
Tubular proteinuria(tubular reabsorption of low mol. Wt. proteiaffected)tubulointerstitial disorder and fanconissyndrome
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2)Glycosuria
DM , renal glycosuria , alimentary glycosuria
Inborn error in metabolism other sugar also present in urine
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3)KetonuriaKetone bodies in sever DM or prolong starvation( acetoaceticbeta hydroxyl butyric acid , acetone )
4)Bilrubinuria
Presence of conj. Bilirubin in urine hepatic or post hepatic jau
Exessive urobilinogen ( normal 1 -3.5 mg /daily ) haemolytic a
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5)HaemoglobunuriaIntravascular hemolysis ( black water fever )
6)Porphobilinogen in urine
Acute intermittent porphyria
Red brown colour (burgundy wine ) IN STANDING URINE
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7)Haematuria
Acute GN , renal stone , malignancy
8)Aminoaciduria
Congenital tubular disorder
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Microscopic examination(centrifusediment)1) Cast
Renal tubule epithelium-----TammHorsfall protein ------coagand washed out by tubular flow
Non cellular cast
Hyaline and granular
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Cellular cast-
Red cell castacute GN
Leucocytic castsacute bacterial pyelonephritis
Epithelial castacute tubular necrosis
Fatty castnephrotic syndrome
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2)Crytal
When uric acid cystal and cysteine crystal present in excess hasignificance
3)Cells
Already covered
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Bacteriological examination
Mid stream sample of urine for pus + bacteria
Urinary tract inf.
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Analysis of blood
This sub. Excreted by kidney
1)Blood urea
20-40mg% , blood urea when 50% glomerular damage occ
2)Plasma creatinine conc.-
0.61.5 mg % , 50% GFR function then significant change i
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3) Serum protein level
Total protein 6.7- 8 gm%(A/G1.7:1)
NEPHROTIC SYNDROME REVERSAL OF A/G ratio
4)Serum cholesterol
150200% , in nephrotic syndrome
5) Serum electrolyte
Value varies with renal disease
Chr. Renal failurehigh k+,PO4 but low Na+ , Ca++
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Renal clearance test
Volume of plasma that is cleared of sub. In one minute by esubstance in urine.
C = Renal clearance
U = urine conc. Of substance
V = rate of flow of urine
P = plasma conc. of substance
C =
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PRINCIPLE GOVERNING RENALCLEARANCE1) Freely filtrated , not reabsorbed and secreted (inulin)
Cin = GFR
2)Freely filtrated , partially reabsorbed
Cx < GFR
3) Freely filtrated , completely reabsorbed(Na+,glucose,A.A.,Cl-)Cx(lowest)
4)Freely filtrated , secreted by tubules not reabsoebed (PAH,diotra
Clearance depends on range of blood flow
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GFR
1) C inulin
Inulin
1)Not exist in body naturally
b)Freely filtered by glomeruli , no absorption or secretion
c)Biologically inert , non toxic
d)Not metabolise or store by kidney
e)Easily lab reading
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Methodiv single bolus , followed by continuous constant i.v inf
Applicaion
1)GFR
2)Indicator of plasma clearance mechanism
3)For comparing clearance of given sub.
Cin (GFR )=Uin V
Pin
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2) C creatinine (as index of GFR , preferred over inulin )
Creatinine
endogenous sub.
0.61.5 mg/dl constant plasma value
Marginally secreted by tubules
Method24 hr urine collected
Plasma conc. Measure at midpoint of urine collection
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C creatinine80 -110 ml / min (normal)
Agemuscle mass GFR C creatinine
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3) C urea
Ureaend product of protein metabolism
Clearance depend on diet
Partially reabsorb by tubule
MethodCompletely void urine and time recorded
After 1hr asked to void again measure conc. in urine
Blood sample collected at midpoint of test
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Maximum urea clearance( C urea(m) ) When urine volume more than
2ml / min
75 ml / min
Standard urea clearance( C When urine volume les
ml/min
54 ml / min
C =
U V
P C =
U V
P
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C urea below 75 % consider serious indicator of renal damag
40% urea reabsorb constantly
so, { C urea 1.2 } in % = GFR
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C PAH
TUBLAR SECRETORY CAPACITY
PAH
Secretion to tubular fluid via carrier in PCT by Tm
when Tm reaches C PAH become more function of glomerular
T m (PAH)
C IN
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RENAL PLASMA FLOW
FICK PRINCIPE
Amount of substance excreted by kidney per unit time ( UV ) renal plasma flow(RPF) multiply by arteriovenous difference iconc.
UV = RPF ( PaPv )
RPF = (PaPv ) / UV
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PAH used for RPF
1)Completely extracted from kidney during each passage via
2)Not metabolise , store or produce by kidney
3)Not affect renal blood flow
4)Conc. Can measure easily
5)Not affect renal flow
6)actively secret by tubules in lumen
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Method
PAH continuous low dose infusion
So, RPF = Pa(PAH) - Pv(PAH) / U PAH . V
But at low dose Pv (PAH) = 0 ( all excreted in urine )
PAH excreted only by kidney so peripheral arterial blood concof Pa(PAH)
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RPF = P PAH / U PAH . V -----------------------------------------(1)
C (PAH) = P PAH / U PAH . V -------------------------------------(2)
By eq.1 and eq.2
RPF = C (PAH)
About 10% of total RPF perfuse to non excretory portion of ki
Renal capsule,renal pelvis
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so, effective RPF = C PAH
i.e. True RPF = C PAH / 0.9
From haematocrit value (Hct) we can also determine the value of Blood Flow (RBF)
RBF = RPF (1/1-Hct)
NORMAL
ERPF = 650 ml/min/1.73 m2 BODY SURFACE AREA (BAS) (M)
ERPF = 600 ml/min/1.73 m2 BODY SURFACE AREA (BAS) (F)
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Cosm and C H2O
1)Osmotic clearance ( Cosm )
Amount of plasma(ml) completely cleared of osmotically activthat appear in urine each minute
3 ml / min
in osmotic diuresis fasting or diet deficient in protein
C osm = Uosm VPosm
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2)Free water clearance ( C H2O )
Volume of pure water that must be removed from or added t
flow of urine ( ml/min) to make it isoosmotic with plasma
Free water generate at ( thick ascending limb and early distal
NaCl reabsorb and free water left in tubules
ADH ABSENTsolute free water excreted , C H20 is positive
ADH PRESENTwater reabsorbed in late DT & CT , C H20 is n
C H20 = V - Cosm
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Relationship between C H20,V & C
1) Iso osmotic urine
V = C osm
AS C H20 = VC osm = 0
Loop diuretics ---- inhibit TAL(THICK ASC. LOOP)--- inhibit dilutinhibition) and conc.(abolish corticopapilary gradient) Capaciturine---isosmotic urine
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2)Hypo osmotic urine
Two virtual volume will form
Cosm contain solute iso osmatic to plasma
C H20free solute waterpositive
V = Cosm + C H20
Excess water intake , central DI , nephrogenic DI
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3)Hyperosmotic urine
-C H20(T CH2O/free water reabsorption)volume of free waneeded to make urine iso osmotic with plasmanegative
Cosm = V + T C H2O
Water deprivation, SIADH
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TEST FOR TUBULAR FUCTION
1)Urine conc. Test
Measure ability of tubules to conc. Urine
Measure sp.gravity of urine after either 12 hr of water depriv12 hr of vasopressin inj.
Sp. Gravity above 1.020 is normal tubular function
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2)Urine acidification test
NH4Cl orally 0.1 gm/kg----urine sample tested for PH after 6 hshould below 5.3(because of liver NH4ClNH3 + HCl)
If more PH inability to excrete H+
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3)Urine dilution test
Pt. ask to drink 1 lit water-----sample collected for every hr. fo
Total 750 ml urine should be excreted
At least one sample should be osmolality less than 100 mOsm
specific gravity less than 1.004
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4)Tubular secretory capacity
Phenolsulphonepthalein Px (PSP) excretion test
PSP inj. i.v. and checked first appearance in urine and quaeliminate in defined period measure functional capacity o
25% dye excreted in 15 min,75% in 2hr (normal)
Slight impairment59 - 40%
Moderate impairment3925%
Marked impairment24 - 11%
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5)Other method to study tubular function
Micro puncture techniqueanalyse tubular fluid at different
Microcryoscopic studyrenal tissue slice at different dept
Microelectrode studymeasure membrane potential of tubu
RADIOLOGY AND RENAL IMAGING
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RADIOLOGY AND RENAL IMAGING
1)Plain radiograph of abdomen
Useful to detect radiopaque stone(Ca++ containing )
2)Intravenous pyelography (IVP)
Inj. i.v. Radiopaque dye ( urographin ) ----- take radiograph of
short interval ( 1,5,10 ,30 min.) -----visualisation of glomerulitubule ultimately renal parenchyma----visualisation of pelvicasystem
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3) Ultrasonography
Quick , non expensive , non invasive method
4)Computed tomography
Detect abnormality in and around of kidney
5)Radionuclide studies
Inj. Of radioactive compound which conc. and excreted by kidgamma camera)
R l bi
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Renal biopsy
VimSilverman needle
Use-
To diagnose proteinuria of unknown origin
Unexplained renal failuar
Systemic disease asso. With kidney
Light , electron , immunofluorescence microscopic study
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SUMMARY
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THANK YOU
Analysis of urine
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Analysis of urine
1)Volume 2)Colour 3)Osmolality and Specific gravity 4)PH 5)Chemical analysis of abnormal urinary constituents6)Microscopic examination 7) Bact
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Countercurrent exchange vs multipl
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Countercurrent exchange vs multipl
Formation of urine
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Formation of urine
Process of urine formation basically involves two steps
Glomerular filtration: formation of ultrafiltrate waste materials of plasma are filtered
Tubular reabsorption: formation of pure urine
PCT & DCT retain water and most of the soluble constituenof the glomerular filtrate by reabsorption
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Renal Functions
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Production of urine
Elimination of metabolicend products
(Urea/Creatinine) Elimination of foreign
materials (Drugs)
Control of volume &composition of ECF
Water and electrolyte
balance Acid/Base status
Endocrine Functions Vit D, Erpo, Renin
Renal threshold
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Renal threshold Renal threshold of a substance is the concentration i
blood beyond which it is excreted in urine
Renal threshold for glucose is 180mg/dL Tubular maximum (Tm): maximum capacity of the
kidneys to absorb a particular substance
Tm for glucose is 350 mg/min
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