Overview WR 2011

8/2/2019 Overview WR 2011

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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.

Documents

Overview WR 2011