overview wr 2011
TRANSCRIPT
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The Multi-
Expertise
of the Kidney
PT 515Clarkson University
Physical Therapy Program
Wilton Remigio, DSc
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Learning Objectives
1. Describe the functional importance of theglomerulus
2. Explain the 3 basic processes of urineformation
3. Describe the control of BP and Water balance
4. Explain renal handling of the majorelectrolytes, organic and inorganicsubstances
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Pathology/Epidemiology
How many patients with kidney disease?
23 million adults age 20 and above
Whats the incidence?
111,000 cases
What are the main causes?
Diabetes, hypertension, glomerulonephritis, and polycystic kidney
disease are the leading causes of ESRD.
ESRD due to diabetes is increasing at an annual rate of more than
11% per year.
How many have had kidney transplant?
In 2007 17,000
How many are waiting for a transplant?
>54,000 patients are awaiting for a donnor
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Recognizing Kidney Disease
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Common signs and complains
Change in frequency and quantity of urine passed,
especially at night (usually increase at first)
Blood in the urine (haematuria)
Foaming urine Puffiness around the eyes and ankles (oedema)
Pain in the back (under the lower ribs, where the kidneys
are located)
Pain or burning when passing urine.
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Symptoms
Tiredness, inability to concentrate
Generally feeling unwell
Loss of appetite Nausea and vomiting
Shortness of breath
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Lifestyle changes
Eat lots of fruit and vegetables including legumes (peas or beans) and
grain-based food like bread, pasta, noodles and rice.
Eat only small amounts of salty or fatty food.
Drink plenty of water instead of other drinks.
Maintain a healthy weight. Exercise regularly.
Dont smoke.
Alcohol has a profound negative effect in eletrolyte, fluid balance and acid-
base balance
Have your blood pressure checked regularly.
Do things that help you relax and reduce your stress levels.
A low protein diet can treat & prevent some kidney conditions and postpone
dialysis
Avoid toxic substances and stress to kidney (post exercise nephritis)
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Renal Multitasking
Regulation of Water and Electrolyte Balance of body fluids (extracellular)
Excretion of Metabolic Waste
Excretion of bioactive substances ( hormones , foreign substances,specifically drugs affecting body function)
Regulation of Arterial Blood pressure
Regulation of Red Blood cell production
Regulation of Vitamin D production
Gluconeogenesis
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Filtration
Blood pressure
Water and solutes across glomerular capillaries
Reabsorption
The removal of water and solutes from the
filtrate
Secretion Transport of solutes from the peritubular fluid
into the tubular fluid
Excretion = urine
Urine formation glossary
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Kidney topography
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Topography cont
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Normal Radiographic Anatomy
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Kidney Topography cont
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The collection of filtrate (urine)
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Name the structures
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The Kidney
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Kidney Perfusion
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Complete Nephron
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Cortical and Juxtamedullary Nephrons
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Filtration
Blood pressure
Water and solutes across glomerular capillaries
ReabsorptionThe removal of water and solutes from the filtrate
Secretion
Transport of solutes from the peritubular fluid intothe tubular fluid
Excretion = urine
Urine formation
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FILTRATION
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THE FILTER Functional Unit
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Afferent and Efferent (hot and cold)
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Filtration
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Glomerular Seive
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Filtration
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Filtration
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Filtration Fraction
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Filtration basics
Proximal Tubule Absorbs 65% of filtered
water , Na+, Cl- and K+.
100% of filtered glucose, AA and smallpeptides is absorbed.
Proximal tubule cell secrete acids and
bases (HCO3). This secretion is a major
route for drugs such as penicillin.
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Glomerular Filtration Rate (GFR)
Arteriolar resistance determines filtration rate.
GFR has to do with how much filtrate is running
down the tubules per unit of time
Fast filtrate will change reabsorption dymanics of
solutes present in filtrate
GFR is used to find how substances are cleared
from the blood (meds) Kidney disfunction -Filtration problems go from
mild to renal failure (need for dyalisis)
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Glomerular Filtration activity
Renal Blood
flow
Glomerular
capillary
pressure
Glomerular
filtration rate
Peritubular
capillary
Pressure
Peritubular
Reabsorption
Afferent
constriction
EfferentConstriction
Afferent
dilation
Efferent
dilation
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REABSORPTION
Proximal Tubule
Thin loop
Distal tubules
Collecting Duct
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Reabsorpsion + secretion
Reabsorption : A two
step process
1.
2.
Reabsorption of water
and most particles
dissolved (solutes)
are linked to theabsorption of Na
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Proximal Tubule-ReabsorptionMicroscopic Anatomy
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Basis for Peritubular
Reabsorption Peritubular capillaries provide
nutrients for tubules and retrieve thefluid the tubules reabsorb.
Oncotic P is greater than hydrostaticP in these capillaries, so thereforeget reabsorption NOT filtration.
Must occur since we filter 180l/day,but only excrete 1-2l/day of urine.
Reabsorb 99% H2O, 100% glucose,99.5% Na+ and 50% urea. Most ofthis occurs at proximal convolutedtubule.
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Tubular Segments
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Reabsorption
Why dont you urinate the same
amount of water you drink?
What creates the transition
between filtration toReabsorption ?
If a substance is not reabsorbed
what happens to it?
What does secreted mean?
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Resorption Thin Descending loop
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Countercurrent MultiplierThe critical characteristics which
create the countercurrent multiplier:1. The ascending limb of the loop of
Henle actively transports Na+ and co-transports Cl- ions out of the lumeninto the interstitium.
2. The ascending limb is impermeableto H2O.
3. The descending limb is freelypermeable to H2O but relativelyimpermeable to NaCl.
4. H2O that moves out of tubule intointersitium is removed by the bloodvessels called vasa recta thusgradients are maintained and H2O isreturned to the circulation.
D A
NaNa X
H2O
H2OX
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A: The tubule is initially filled with isotonic fluid
B: Na is pumped out of the ascending loop, raisingthe osmotic pressure outside and lowering it
inside. Note that the maximum gradient (inside to
out) is 200 mosm/L
C: Water flows out of the descending tubule by
osmosis, raising the osmotic pressure in the
descending tubule to 400 mosm/L
D: Fresh fluid enters from the glomerulus, pushing
concentrated fluid (400 mosm/L) into the
ascending limb
E: In the 2nd round the Na pump produces another
200 mosm/L gradient across the membrane, but it
is starting from a more concentrated solution, sothe external osmolarity rises to 500 mosm/L.
F: The 3rd round of Na pumping raises interstitial
concentration to 700 mosm/L, and so on.
The pumping, osmotic flow and filtration flows are
shown as separate activities, but in reality they occur
together as a continuous process.
Countercurrent Multiplier
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formation of
hyperosmotic urine
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Role of urea in concentrating urine
Urea very useful in concentrating urine.
High protein diet = more urea = more
concentrated urine. Kidneys filter, reabsorb and secrete urea.
Urea excretion rises with increasing
urinary flow.
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Urea recycling
Urea toxic at high
levels, but can be
useful in small
amounts.
Urea recyclingcauses buildup of
high [urea] in
inner medulla.
This helps createthe osmotic
gradient at loop of
Henle so H2O can
be reabsorbed.
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Juxta Glomerulus Apparatus
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Resorption- Collecting Tubules
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Summary
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Kidney Function Overview
Efferent
arteriole
Afferentarteriole
Glomerulus
Peritubular capillaries
Proximal
tubuleBowmans
capsule
Collecting
duct
To
renal
vein
F
R
S
E
F
R
S
R R
R
S
R S
E
Loop
of
Henle
To bladder and
external environment
= Filtration: blood to lumen
= Reabsorption: lumen to blood
= Secretion: blood to lumen
= Excretion: lumen to external
environment
KEY
Distal
tubule
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Histology
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Review Blood volume and Pressure
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Studies cited
Clin Nephrol. 1998 Nov;50(5):273-83.
Effect of a ketoacid-aminoacid-supplemented very low protein diet on the progression of advanced renal disease: a
reanalysis of the MDRD feasibility study.
Teschan PE, Beck GJ, Dwyer JT, Greene T, Klahr S, Levy AS, Mitch WE, SnetselaarLG, Steinman TI, Walser M.
Vanderbilt University, USA.
J Am Soc Nephrol. 1999 Jan;10(1):110-6.
Can renal replacement be deferred by a supplemented very low protein diet?
WalserM, Hill S.
J Nephrol. 2001 Nov-Dec;14(6):433-9.
Low protein diets and outcome of renal patients.
Aparicio M, Chauveau P, Combe C.