1 renal physiology part two renal physiology details

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Renal Physiology

PART TWORenal Physiology details

Basic Mechanisms of Urine Formation

Filtration, secretion, reabsorption and excretion.

How do we determine these rates?

The master equation:Rate of excretion = filtration +

secretion – reabsorption

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TERMS

Urinary output is a flow rate; how much urine are you producing per unit of time, ml/min

This refers to the amount of urine dripping into the urinary bladder, not the amount voided.

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TERMS

Rate of filtration is the flow rate of plasma fluid going into Bowman’s capsule.

This plasma fluid is called “filtrate”. The filtrate is not the same as plasma since

there are no plasma proteins in it (proteins don’t get through the filtration membrane, not just because of their size, but also because of their negative charge).

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TERMS

Glomerular Filtration Rate (GFR) is the amount of fluid going into Bowman’s capsule per unit of time.

Dissolved in that filtrate are electrolytes, glucose, and amino acids. We can also calculate how much of those molecules are entering Bowman’s capsule.

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TERMS

Filtered Load (or Tubular Load) is the amount of a specific solute (electrolyte, glucose, or amino acid) dissolved in the fluid that enters Bowman’s capsule. There is an equation for this, but you have to know two things:

Plasma concentration of that solute. To determine this, draw blood, place in

spectrophotometer.

Patient’s GFR

TL s = Ps x GFR

Filtrate vs. Solute

If I had a cup and I filled it with 125ml of water, and then added one packet of Crystal light, how much fluid entered the cup? 125 ml.

How much fluid (the filtrate) went into the cup is the GFR.

If you know how much solute (Crystal light) went into the cup, you can calculate the filtered load.

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How to calculate Tubular Load

If we want to know how much glucose was filtered into the nephron, we need to know that person’s blood plasma glucose levels, and we would need to calculate their GFR.

Each individual solute will have its own tubular load calculation.

TL sodium = Psodium x GFR

TL chloride = Pchloride x GFR

TL glucose = Pglucose x GFR

Kidney Function and Aging

With age, our filtration membranes deteriorate, and we also lose some of our glomeruli.

With age, the permeability of our kidney membranes also declines, causing a decline in GFR.

Thus, we have a decline of urine production, gradually over our lifetime.

Some people age better than others with our skin, some age better with their GFR.

Older people have to take a lower dosage of medicines that are excreted in the urine.

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Solutes Suck!

Sodium (Na+) is the most numerous of the solutes in our plasma.

Remember, if solutes are being reabsorbed, water will come with it….solutes SUCK water!

When salt is reabsorbed, water will be reabsorbed too. When salt is secreted, water is secreted too.

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Solutes Suck!

Some solutes are being reabsorbed, pulling water with them, but other solutes are not being reabsorbed, so they are trying to keep water with them.

If there are more particles being reabsorbed, the water will mostly be reabsorbed also.

What will happen to the concentration of the particles that are not being reabsorbed? Their concentration will go up.

Those things that are not reabsorbed will leave the body.

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For any substance,

The rate of = rate of + rate of – rate of excretion filtration secretion reabsorption

Renal Equations

Other terms that are used to express these ideas:

•For “Rate of excretion” we often use the term “urinary output”

•For “Rate of filtration,” when referring to filtered fluid, we often use the term GFR (glomerular filtration rate)

if referring to filtered solute, we use TL (Tubular Load)

(Urinary output) (GFR or TL)

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Calculating Tubular Load of a Substance (any solute, “s”)

At the glomerulus, fluid and solutes (solids that were dissolved in the fluid) are constantly being filtered and enter the kidney tubules.

GFR is the term for the volume of plasma fluid filtered each minute.

Once in the tubule, it is “tubular fluid” and no longer plasma, but not yet urine.

Tubular Load (TLs): the amount of any substance (s) entering the tubule, each minute.

TL depends on two things: the plasma concentration of the solute and the rate of filtration of that solute

TL s = Ps x GFR

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Tubular Filtrate Resembles Plasma

By far, filtered fluid is mainly NaCl and water.

But it also contains other salts and electrolytes, amino acids, small sugars, vitamins and other small molecules, such as wastes.

Na+ and Cl- are present in such large amounts; they are over 99% reabsorbed along the length of the tubule. (Why? We need it to keep our blood pressure up)

At a constant GFR, as plasma concentration of a freely filtered substance rises, the tubular load of the substance rises in direct proportion to plasma concentration

Remember the route the fluid takes:Glomerulus Proximal convoluted tubule (PCT) Descending limb of LOH Ascending limb of LOH Convoluted tubule Collecting duct

Loop of Henle, thick ascending limb

Loop of Henle

descending limb

Collecting duct

Distal convoluted tubule

Proximal convoluted

tubule

Glomerulus

Solutes are reabsorbed into the blood stream

The next photo is of a Proximal Convoluted Tubule (PCT), just beyond the glomerulus. The lumen of the tubule contains the filtrate which leaked out of the capillaries and into the glomerulus, entered Bowman’s capsule, and has now arrived in the PCT.

There are cells (tubular cells) lining the lumen of the PCT. The cells have proteins that allow some solutes to diffuse into the cell, and right back out cell, and into the peritubular capillaries that surround the PCT. In that way, solutes re-enter the blood stream.

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Lumen of PCT

Tubular Cells

Filtrate arriving from Bowman’s Capsule

Peritubular Capillaries

Proximal Convoluted Tubule

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PCT

PCT

Proximal Convoluted Tubule Water will follow the solutes. The PCT is the biggest site for reabsorption

of solutes (substances dissolved in water). 100% of glucose and amino acids are

reabsorbed in the PCT. 67% of Na and water are reabsorbed here. If ADH levels are very high, most of the water will

be reabsorbed in the PCT.

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Water reabsorption along the proximal convoluted tubule (PCT) occurs by osmosis resulting primarily from reabsorption of sodium

Proximal Convoluted Tubule In a state of acidosis, the PCT will secrete H+

ions. When the H+ ions are secreted, reabsorption of

bicarbonate ions occurs at the same time. H+ ions are also secreted in the DCT, but

bicarbonate cannot be reabsorbed there.

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Pressures

Because we drop off 125 ml of filtrate into Bowman’s capsule every minute, the water pressure in the peritubular capillary beds is low.

Because proteins cannot get through, the osmotic force is very high here (proteins are trying to get in, but cannot).

In the glomerulus, the forces favor fluid to leave the glomerulus and enter Bowman’s capsule.

In the peritubular capillary bed, the forces favor the fluid to enter the capillary bed.

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Solutes without transporters

There are some solutes that cannot get through the tubular cell membranes because they have no protein transporters, so they become more concentrated in the tubular lumen.

The concentration increases until they are forced to diffuse down their concentration gradient and then they can enter the tubular cells and be reabsorbed.

One such solute is chloride (Cl-).23

Active Transport

Active transport, facilitative transport, and simple diffusion are all involved in renal clearance.

It all starts in the membrane of the tubular cells proteins that allow Na+ and K+ to get through. This is called Active transport (it requires ATP, so it uses energy).

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Glucose reabsorption

Glucose and amino acids leave the tubule and enter the peritubular capillaries. That is reabsorption.

When any substance leaves the bloodstream and enters the lumen of the kidney tubules, it is secretion.

By adjusting reabsorption and secretion, your body adjusts its acid-base balance; if too many H+ ions were kept, there is too much acid, and the H+ ions will start to be secreted more.

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Transport Maximum

When proteins are shuttling solutes, the rate of this shuttling has a maximum, called a transport max (Tm).

If there are more solutes present than can be transported, the solutes will end up in your urine. There will be a point at which you can saturate these transporters. For instance, when your blood glucose levels are elevated because you have a problem making insulin or responding to insulin, then you will have an increase in glucose load in Bowman’s capsule. This excess filtered load will cause a spill of glucose into the urine.

After the PCT, there are no more glucose transporters to reabsorb it. 320 is the max rate to filter glucose. If you filter 125 and reabsorbed 125, how much did you excrete? None. If you filter 375 but reabsorb 320 (transport maximum), 55 is excreted

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Threshold

Transport maximum is the total transport maximum throughout all of the nephrons in the kidney. They do not all have the exact number and type of transporters.

One single nephron might get to maximum and a tiny amount of glucose will appear in the urine. As more nephrons reach their maximum, more glucose will appear in the urine.

That appearance of glucose in the urine before you reach the overall Tm of the kidney is called threshold.

Threshold is the plasma concentration at which a substance begins to appear in the urine

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1

2

3

4

5

=solute= transporter

Transport maximum is reached when carriers are saturated.

5/min

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1

2

3

4

5

=solute= transporter

Transport maximum is reached when carriers are saturated.

5/min

Excretion

Calculate Glucose Excretion

Step 1: Calculate their filtered load: GFR x plasma glucose level 90 x 2

Step 2: Determine reabsorption of glucose (maximum is 150).

Step 3: Subtract 150 from 180, and that tells you their excretion.

Excretion = filtration – reabsorption Answer 180 – 150 = 30 mg/min

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A patient with uncontrolled diabetes has aGFR of 90 ml/min, a plasma glucose of 2mg/ml, and a transport max (Tm) shown in the figure. What is the glucose excretion for this patient?

.

Reabsorbed

Excreted

TransportMaximum(150 mg/min)

Threshold

250

200

150

100

50

0

Glu

cose

(m

g/m

in)

a. 0 mg/minb. 30 mg/minc. 60 mg/mind. 90 mg/mine. 120 mg/min

50 100 150 200 250 300 350Filtered Load of Glucose

(mg/min)Copyright © 2006 by Elsevier, Inc.

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.

Reabsorbed

Excreted

Threshold

250

200

150

100

50

0

Glu

cose

(m

g/m

in)

Filtered Load of Glucose(mg/min)


GFR = 90 ml/min PGlu = 2 mg/mlTmax = 150 mg/min

50 100 150 200 250 300 350


Copyright © 2006 by Elsevier, Inc.

Excretion = filtration (GFR x Pglu) – reabsorption (Tmax) 180 – 150 = 30 mg/min

Answer:

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A patient with uncontrolled diabetes has aGFR of 90 ml/min, a plasma glucose of 2.33mg/ml, and a transport max (Tm) shown in the figure. What is the glucose excretion for this patient?

.

Reabsorbed

Excreted


Threshold

250

200

150

100

50

0

Glu

cose

(m

g/m

in)


50 100 150 200 250 300 350Filtered Load of Glucose

(mg/min)Copyright © 2006 by Elsevier, Inc.

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Answer:

.

Reabsorbed

Excreted

Threshold

250

200

150

100

50

0

Glu

cose

(m

g/m

in)

Filtered Load of Glucose(mg/min)


GFR = 90 ml/min PGlu = 2.33 mg/mlTmax = 150 mg/min

50 100 150 200 250 300 350


Copyright © 2006 by Elsevier, Inc.

Excretion = filtration (GFR x Pglu) – reabsorption (Tmax) 210 – 150 = 60 mg/min

Urea

Urea is also reabsorbed in the PCT.Urea is a waste product…how will we

get rid of it?We will reabsorb it now and secrete

it again further along in the nephron.

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Salt concentration in the PCT

As you go along the length of the PCT, the amino acids and glucose are reabsorbed, in addition to salt and water.

The salt concentration in the filtrate stays the same as the blood plasma salt concentration.

As we go through the rest of the nephron, the saltiness will diminish as it becomes more like urine and less like plasma.

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Diuretics in the PCT

LasixMannitol

cause diuresis by reducing net water reabsorption from the proximal convoluted tubule

“Potassium sparing” refers to a diuretic’s tendency to decrease potassium excretion

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Diuresis in the PCT

Diuresis means the person is excreting a lot of water. This is what happens in diabetes mellitus. It makes the person thirsty, so they drink a lot of water.

However, that is not why they have diuresis.The reason for the diuresis is the large

amount of glucose in the tubule draws water with it, since glucose is a particle.

Thus, the large filtered load of glucose has an osmotic effect on the tubule

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Summary of PCT functions

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Reabsorbs 2/3 of the salt and waterReabsorbs 100% of glucose and amino acidsReabsorbs 65% of potassiumReabsorbs 50% of ureaRegulates pH in the filtrate Secretes creatinine (waste product after you eat protein) into the filtrate

Now we leave the PCT and enter the Loop of Henle

Our kidneys are responsible for adjusting the urinary output.

They are responsible for determining if you have a lot of urine which very dilute, or scant, concentrated urine.

If you drink a lot of water, it will make your urine dilute (more water than solutes).

If you are dehydrated, your urine will be concentrated (more solutes than water).

Caffeine and alcohol are dehydrating, so they have the opposite effect of drinking water. They block antidiuretic hormone (ADH) too.

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Before we move onto the Loop of Henle, be mindful of the following:

How can you make a solution more concentrated? Take out water or add more solute.

How can you make a solution less concentrated? Add water or take out more solute.

Your kidneys play that game. To do that, we have to separate solutes and water. But how do we do that, since water follows particles? There are several parts of the nephron that are impermeable to water.

Ascending limbDescending

limb

Loop of Henle

LOOP OF HENLE: Descending Limb

Water is reabsorbed Na+ and urea are secreted

What will your filtrate taste like here? We are removing water and adding salt.

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Keep track of the water:

20% of water is reabsorbed in the descending limb, and 67% was reabsorbed in the PCT. That means a total of 87% of our filtered water has now been reabsorbed. The remaining 13% can be tapped into if your body needs it. If you are well hydrated, it will go into the toilet. If you are dehydrated, hormones will be needed farther along in the nephron in order to reabsorb more water.

In the PCT, you have reabsorbed 50% of urea. Although it is a waste product, we use it to create an osmotic gradient to reabsorb glucose and other good solutes. Now, we want to get rid of the urea since we are done reabsorbing all the glucose.

By the time the filtrate is at the tip of the LOH, all 50% of that urea has been secreted back into the lumen, plus some more. The descending limb contains 110% of the urea you initially filtered.

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LOOP OF HENLE: Ascending Limb

Impermeable to water, so no water is reabsorbed or secreted.

Permeable to NaCl and urea:NaCl (or sodium and chloride

separately) diffuses out of tubule (reabsorbed)

Urea diffuses into tubule (secreted)

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Saltiness in the LOH

Now let’s take the LOH together: on the descending limb we have water leaving and salt entering the lumen.

On the ascending limb, we have salt leaving, and no more water leaving the lumen.

As it goes up the ascending limb, it is becoming more and more hypo-osmotic (less and less salty). At the top of the ascending limb, it tastes less salty than blood plasma.

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Now we leave the LOH and enter the distal convoluted tubule (DCT)

Distal convoluted tubule

Early DCT

Late DCT

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Early Distal Convoluted Tubule (DCT)

A thiazide diuretic is one that blocks sodium-chloride channels, so that sodium cannot be reabsorbed, so water cannot be reabsorbed.

This will cause water loss, which will lower blood pressure.

Thiazide diuretics have their effect in the early distal convoluted tubule.

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Distal Convoluted Tubule (DCT)

5% more sodium is reabsorbed The DCT activity can be influenced by

hormones. If there are no hormones around, these cells don’t do anything; whatever is remaining in the lumen will go into the bladder.

If there are no hormones, the last 13% of water and the last 3% of Na goes into the toilet.

Anti-diuretic hormone (ADH) and aldosterone will cause more water and salt to be reabsorbed (raises blood pressure).

Distal Convoluted Tubule (DCT)

Special cells in the DCT, called intercalated cells manage your acid-base balance, to secrete more H+.

If you are in a state of acidosis (too much acid in your blood) because you drank alcohol, your intercalated cells will secrete more H+ to bring the pH back to normal.

If you are in a state of alkalosis because you have been hyperventilating (breathing fast), will the intercalated cells increase H+ reabsorption or H+ secretion?

Answer: increase H+ reabsorption.

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We’ve covered filtration and reabsorption….Now, it’s time for Tubular Secretion

Secretion = Excretion – Filtration+ reabsorption

Secretion

Secretion is the opposite of reabsorption. Any time you see a solute going from the tubular cells and into the lumen, it is called secretion. Secreted substances end up in the urinary bladder.

It happens by active transport. We secrete acids, bases, phosphates, excess potassium.

Secretion works this way: solutes diffuse out of the peritubular capillary bed and into the tubular cells, then they enter lumen of the convoluted tubule. From there, they go out the collecting duct, and into the urinary bladder.

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Long-Term Dehydration

Compensations in a dehydrated person who is deprived of water for 36 hours include the following: increased plasma renin increased plasma ADHdecreased concentration of plasma atrial

natriuretic hormone (vasodilator, made by the heart)

increased water permeability of the collecting ductdecreased water permeability in the ascending

loop of Henle

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Hormones affecting the kidney

Renin: released by kidney when blood pressure is too low ACE: Pulmonary capillary enzyme that responds to renin. When renin

is elevated, it cleaves angiotensin I into angiotensin 2. Angiotensin II: causes blood vessel constriction to increase blood

pressure. It also stimulates the release of aldosterone. Aldosterone: Secreted from the zona glomerulosa of the adrenal

cortex. It increases blood pressure by increasing sodium reabsorption.

ADH: Promotes aquaporin insertion in the cell membranes of the tubules Aquaporin is a protein that allows water to pass through the cell

membrane, to be absorbed out of the tubule. Atrial natriuretic peptide (ANP): heart hormone that promotes

more diuresis and urine production to lower blood pressure. It is primarily released due to elevated potassium levels.

Adenosine: Macula densa use this to molecule to change the radius of the afferent arteriole. 54

Summary of What’s Going On

GlomerulusCapillary hydrostatic pressure is very high

here (about 60mmHg). Bowman’s capsule colloid osmotic pressure here is essentially

zero

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PCT part of the nephron normally reabsorbs the most water Site of sodium-glucose co-transport as well as sodium-

amino acid co-transport Even though reabsorption is occurring, tubular fluid is

isosmotic to plasma throughout the length of this region.

Site of most potassium reabsorption when no aldosterone is present

secretes hydrogen, is rich in carbonic anhydrase, and accounts for most bicarbonate reabsorption

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Descending Limballows secretion of sodium and urea and

is permeable to waterThese are highly permeable to water,

low permeability to solutes, and are considered diluting segments.

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LOHhave the maximally hyperosmotic fluid

when ADH levels are high At the Tip of the LOH

Tubular fluid here is always maximally hyperosmotic to plasma, and is not hormone sensitive

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Thick ascending limbhas the Na+/K+/Cl- co-transporteris sensitive to the diuretic furosemide

(lasix). are impermeable to water, reabsorb

solutes, and are considered diluting segments.

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DCTMacula densa is found hereis sensitive to sodium channel blockers

like amiloride and aldosterone inhibitorsSite of hormonally regulated potassium

secretionThe intercalated cells of this region

secrete hydrogen, is rich in carbonic anhydrase, and makes “new” bicarbonate.

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Collecting Ducthave the maximally hyperosmotic fluid

when ADH levels are high

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NOTE: Print the following slide and write notes on what is going in and what is coming out of each area of the nephron.

62Loop of Henle (tip)

Thick Ascending Limb

Proximal convoluted

tubule

Glomerulus

Late Distal convoluted tubule

Collecting duct

Descending limb

Bowman’s capsule

Vasa recta

Early Distal convoluted tubule

Clinical Correlations

What are the symptoms of severe dehydration?

1. Disoriented2. Falls unconscious3. Measurable loss of weight during strenuous activity (water loss)4. Blood pressure drops

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A marathon runner becomes dehydrated during a race.

1. What will happen to their weight?2. What will happen to blood volume?3. What will happen to blood pressure?4. What will happen to heart rate?5. What will happen to their baroreceptors?6. What will happen to sympathetic outflow?

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1. Weight goes down (water loss)2. Blood volume decreases (water loss)3. Blood pressure decreases (volume loss)4. Heart rate increases (b/c of decreased BP)5. Baroreceptors decrease firing (low BP)6. Sympathetic outflow increases (to

compensate)65



1. What will happen to their Renal blood flow (RBF)?

2. What will happen to their tubular load of sodium?

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1. Renal blood flow (RBF) will decreaseThe body does not want to lose more

water2. Tubular load of sodium will decrease

Sodium is reabsorbed so water will come with it

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1. What hormones would compensate for this condition?

These would all be elevated:ReninAngiotensin IIAldosteroneADH

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1. What will be the urinary output?Low volume

2. What will be the urine concentration?High concentration

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A marathon runner becomes dehydrated during a race and falls unconscious.

1. What type of shock is this?Hypovolemic shock

2. What is the treatment?I.V. saline/bicarbonate solution

Giving saline will increase water retentionGiving bicarbonate will reduce acidosis

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Clinical CorrelationsA marathon runner becomes dehydrated

during a race and falls unconscious.1. Why do they have acidosis?

Hypovolemic shock reduces oxygen delivered to tissues.

Muscles without oxygen start to convert to anaerobic metabolism to get their ATP. The waste product of anaerobic metabolism is lactic acid.

The buildup of lactic acid without the kidney excreting it causes metabolic acidosis.

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Clinical CorrelationsJanuary 12th, 2007, A 28 year-old mother

of three from Sacramento decides to go on a radio program to compete in a contest called, “Hold your Wee for a Wii.”

During this contest, contestants drank great volumes of plain water.

After the contest, she called her co-workers to say she wasn’t coming to work because her head hurt so badly.

Later she is found dead. 72


Drinking too much water changes the extracellular osmolality. When the plasma is too dilute (too much water, too few solutes), water will leave the bloodstream to enter the tissues, where there are more solutes (solutes SUCK!).

Water will enter the tissues (intracellular body fluid compartment), including the brain.

The excess water will cause the brain to swell. 73

Water moves through Compartments

Intracellular water (or other fluid) is the watery substance inside a cell. Interstitial water (or other fluid) is the watery substance between cells. Extracellular water (or other fluid) is the watery substance that is outside

of cells. Some of it may be interstitial, some may be in the blood, joints, CSF, etc.

The concentration of individual solutes (glucose, sodium, potassium, chloride) is different in intracellular fluid than it is in extracellular or interstitial fluid, but the total osmolarity (concentration of all the solutes combined) of the intracellular fluid, extracellular fluid, and interstitial and is the same.

Water can move from one compartment to another. It can be drawn out of the plasma to enter the interstitial compartment first, and then it may enter the cells.

Water can also move from the cells to the interstitial compartment, then into the bloodstream.

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Water/Salt Imbalance Problems

Expansion: the body has retained too much water Contraction: the body has too little water

Hypo-osmotic volume The water in the body has too much water, too few solutes

Hyperosmotic volume The water in the body has too little water, too many solutes

Isosmotic volume The water in the body has the proper balance of water and

solutes.

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Water/Salt Imbalance Problems Hypo-osmotic volume expansion

Excessive water drinking; plasma osmolality is reduced from too much water, not enough solutes (hypo-osmotic) and the extracellular fluid (outside of cells) volume has increased (expansion).

Hypo-osmotic volume contraction Excessive sweating; the person has lost a lot of salt, but has lost

some water, too. They are dehydrated (contraction) and have low salt levels (hypo-osmotic). The water in the body has low osmolality due to loss of the salt.

Hyperosmotic volume expansion High salt intake; there is too many solutes, water is retained, so

the overall volume is increased (expansion), but there is a lot of salt, so osmolality is increased (hyperosmotic).

Hyperosmotic volume contraction Dehydration; the person has lost a lot of water, so overall volume

is decreased (contraction). The salt level has not changed, so that means more salt dissolved in less water (hyperosmotic).

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Water/Salt Imbalance Problems

Isosmotic Volume ContractionDiarrhea; loss of water and solutes. Overall

water/salt balance is maintained (isosmotic), but person loses overall volume (contraction).

Isosmotic Volume ExpansionSalt Infusion; person receives an i.v. of normal

saline (isosmotic), and overall volume of body fluid increases (expansion).

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Hyperosmotic volume contraction

There would be elevated protein concentration but NO CHANGE in hematocrit with this condition

Diabetes insipidus would cause this condition

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Hyperosmotic volume expansion

Conn’s disease would cause this condition

There would be decreased protein concentration and hematocrit

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Hypo-osmotic volume contraction

Addison’s Disease would cause this condition

There would be increased protein concentration and hematocrit

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Hypo-osmotic volume expansion

Syndrome of inappropriate ADH would cause this condition

There would be decreased protein concentration but NO CHANGE in hematocrit with this

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Iso-osmotic volume expansion

There would be decreased protein concentration and hematocrit

Infusion of a 0.9g% saline solution would cause this condition

In these conditions there would be NO CHANGE in the intracellular volume nor osmolality

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Iso-osmotic volume contraction

In these conditions there would be NO CHANGE in the intracellular volume nor osmolality

There would be increased protein concentration and hematocrit

Diarrhea or burns would cause this condition

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Hypernatremia(excess sodium in the blood)

Causes Hypovolemic

Inadequate intake of water, typically in elderly or otherwise disabled patients who are unable to take in water as their thirst dictates. This is the most common cause of hypernatremia.

Euvolemic Excessive excretion of water from the kidneys caused

by diabetes insipidus, which involves either inadequate production of ADH or kidneys not responding to it.

Hypervolemic Intake of a hypertonic fluid such as drinking seawater or

receiving an i.v. of sodium bicarbonate after a vigorous resuscitation. Can also be caused by mineralocorticoid excess due to a disease state such as Conn's syndrome or Cushing's Disease

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Hypokalemia(low potassium in the blood)

Mild hypokalemiaOften without symptoms, although it may

cause a small elevation of blood pressure, and can occasionally provoke cardiac arrhythmias.

Moderate hypokalemiaMay cause muscular weakness, myalgia

(muscle pain), and muscle cramps Severe hypokalemia

May cause flaccid paralysis and hyporeflexia

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Hypokalemia(low potassium in the blood)

Causes Inadequate potassium intake (rare)Gastrointestinal loss (vomiting or diarrhea)Urinary loss

Thiazide diuretics Alkalosis in the blood Disease states that cause high aldosterone levels

Conn’s syndrome (hyperaldosteronism) Cushing's syndrome (excess cortisol binds to the

Na+/K+ pumps, so it acts like aldosterone).

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Addison’s DiseaseConn’s DiseaseDiabetes MellitusDiabetes InsipidusCushing’s DiseaseKnow which of these diseases has

hypernatremia, hypokalemia, hypo or hyperglycemia, etc.

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Addison’s Disease

Chronic adrenal insufficiency (low cortisol levels)

HyponatremiaHypoglycemiaPossible death at times of extreme

stress

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Conn’s Disease

This is hyperaldosteronism. The person releases too much

aldosterone, which increases sodium retention, so water follows, and hypertension results.

Condition associated primarily with hypertension and mild hypernatremia and mild hypokalemia. No diabetogenic (glucose) problems.

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Diabetes Mellitus Condition characterized by polyuria, glucosuria, polydipsia

and ketonuria. Polyuria (frequent urination) Glucosuria (glucose in urine) Polydipsia (thirsty) Ketonuria (ketones in the urine)

When insulin does not pull glucose into the body cells, it stays in high levels in the blood (hyperglycemia) and spills out in the urine (glucosuria). The body is starving, so it breaks down fat into fatty acids for energy, and ketones are the waste product. In small amounts, they are broken down in the liver, but in large amounts, they build up in the blood (ketoacidosis: lowers blood pH) and spill out into the urine (ketonuria). Starvation, fasting, prolonged vomiting, high protein diets, and low carbohydrate diets also cause this condition.

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Diabetes Insipidus

Condition characterized by polyuria and polydipsia, but not glucosuria.

This is more like a disease of water loss (ADH is not produced).

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Cushing’s Disease

HypernatremiaCaused by lack of water in the blood, like

dehydration. Hypokalemia (low potassium) Hyperglycemia (excess glucose) Diabetes mellitus Weight gain, particularly of the trunk and face

with sparing of the limbs (central obesity), moon face, buffalo hump, and sometimes growth of facial hair.

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Tests to assess kidney function

BUN (Blood Urea Nitrogen or Urea Nitrogen) Creatinine BUN/Creatinine Ratio Calcium Sodium Potassium Chloride CO2

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BUN (Blood Urea Nitrogen or Urea Nitrogen). This is the concentration of nitrogen (within urea) in the serum (but not in red blood cells). A waste product, derived from protein breakdown, produced in the liver and excreted by way of the kidneys. High values may mean that the kidneys are not working as well as they should. BUN is also elevated by blood loss, dehydration, high protein diets and/or strenuous exercise which may temporarily and artificially raise levels. A low BUN level may be the result of liver disease, a low protein diet, pregnancy, or drinking an extreme amount of water.

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Creatinine. A waste product largely from muscle metabolism (breakdown). Concentration of creatinine in the blood depends upon the amount of muscle that you have and the ability of your kidneys to excrete creatinine. High values, especially with high BUN levels, may indicate problems with the kidneys. Low values are generally not considered significant. BUN/Creatinine Ratio - This ratio is sometimes used or diagnostic purposes.

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Calcium. Calcium is one of the most important elements in the body. The parathyroid glands and the kidneys control the amount of calcium in the blood. The parathyroid gland is the main regulator of calcium in the body. Nearly all of the calcium in the body is found in bone (99%). The remaining 1% is very important for proper clotting, nerve, and cell and enzyme activity. An elevated calcium level can be due to medication (such as too much synthetic vitamin D), inherited disorders of calcium handling in the kidneys, bone disease, or excess parathyroid gland activity or vitamin D. Low calcium can be due to malnutrition, drugs and certain metabolic disorders.

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Sodium. An electrolyte regulated by the kidneys and adrenal glands. This element plays an important role in the water/salt balance in your body.

Potassium. Potassium is an electrolyte found primarily inside cells and must be controlled very carefully by the kidneys. Its role is to maintain water balance inside the cells and to help in the transmission of nerve impulses. A low potassium level can cause muscle weakness and heart problems. A high potassium level can be found in kidney disease or in over ingestion of potassium supplements.

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Chloride. Chloride is an electrolyte regulated by the kidneys and adrenal glands. Chloride is important to the function of nerves, muscles, and cells. It is usually associated with a high or low level of sodium or potassium.

Some drugs taken by prostate cancer patients such as estrogens and corticosteriods can cause increased chloride.

CO2. Co2 levels reflects the acid status of your blood. Corticosteriods as well as kidney disease can be involved.

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1 renal physiology part two renal physiology details

Documents

p glucose x gfr slide

p s x gfr slide

solutes suck water

p chloride x gfr tl

terms rate of filtration

flow rate of plasma

p sodium x gfr tl chloride

plasma proteins