physiological basis of evaluation of rf

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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physiological basis of evaluation of rf

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