PBL 3

Question 1

Abdominal bruit

Answer 1

this is a murmur sound that is generated by turbulent flow of the blood in an artery due to partial obstruction

Question 2

Renal artery stenosis

Answer 2

this is the narrowing of one of the renal arteries due to atherosclerosis, narrowing of the renal artery can impede blood flow to the kidney and result in renovascular hypertension

Question 3

Angioplasty

Answer 3

this is a procedure that is used to widen blocked or narrow coronary arteries, this procedure is done using a balloon to stretch open a narrowed or blocked artery

Question 4

Occlusion proteinuria

Answer 4

this is protein in the urea caused by a blockage or closing of a blood vessel

Question 5

Creatinine

Answer 5

this is a compound that is produced by metabolism of creatine and is excreted by the kidney in the urine

Question 6

Describe the vascular anatomy of the kidney

Answer 6

• The renal arteries branch of the abdominal aorta and supply the kidneys with blood
• Arterial supply of the kidneys vary from person to person, and there may be one or more renal arteries supplying each kidney
• The right renal artery is longer than the left renal artery due to the position of the IVC
• Renal arteries carry a large portion of the total blood flow to the kidneys
• ¼ of CO pass to the kidneys and are filtered by the kidneys
• Renal blood supply starts with the branching of the aorta in the renal arteries and ends with the exiting of the renal veins to join the IVC
• Renal arteries split into different segmental arteries upon entering the kidneys which then split into several arterioles
• Afferent arterioles larger diameter than efferent arterioles
• The afferent arteriole branch into the glomerular capillary which transfer fluid into the glomerulus and into the bowman’s capsule
• Efferent arteriole takes blood away from the glomerulus and into the interlobular capillaries these provide tissue oxygenated to the parenchyma of the kidney

Question 7

what is the GFR

Answer 7

the GFR is the total amount of fluid filtered through all the glomeruli in both the kidneys

Question 8

what is the average GFR

Answer 8

120-125 ml/min

Question 9

what is urine flow and why is it different from the GFR

Answer 9

Urine flow is amount 1 ml/min – it is different because most of the fluid filtered is therefore reabsorbed

Question 10

what is GFR used for

Answer 10

Used to measure the level of kidney function and determine the stage of kidney disease

Question 11

what happens if the GFR is below 60 for more than 3 months

Answer 11

If a GFR is below 60 for three months or more or a GFR above kidney with damage indicates chronic kidney disease

Question 12

what happens to the GFR and RPF when the kidneys are damaged

Answer 12

If the kidneys are damaged generally the GFR will decrease but the RPF may be normal, measurement of GFR is essential test of kidney health

Question 13

define clearance

Answer 13

Clearance is the effective volume of plasma that is completely cleared of a substance per minute

Question 14

How do you measure clearance

Answer 14

• used to measure the GFR

- measured in the units volume/time

Question 15

what are the three outcomes of what clearance equals

Answer 15

1. Not at all removed by the kidney – clearance = 0
2. Removed at the same rate as water passes through the glomeruli – clearance = GFR
3. Completely removed from blood passing through kidney – clearance = RPF

Question 16

what is the clearance formula

Answer 16

urine concentration/plasma concentration x urine flow

Question 17

how do you measure clearance of a substance

Answer 17

1. Measure the concentration of the substance in the plasma
2. Collect urine for a fixed period to get the urine flow ml/min
3. Measure the concentration of the substance in the collected urine

Question 18

What do you use to measure clearance

Answer 18

• Inulin usually used, it is a polysaccharide and is completely filtered in the plasma and not absorbed
• Inulin does occur naturally in the plasma so you have to infuse inulin over a period of hours to reach a steady plasma concentration this makes it impractical
• Creatinine clearance is used to measure GFR, produced naturally by the body and is freely filtered by the glomerulus
• Creatinine is the product of creatine metabolism
• 10-20% error margin,
• Already at a steady state concentration in the blood
• You can make an approximation just on the blood levels only

Question 19

what is the normal creatinine clearance

Answer 19

• Women 88-128 mL/min

- Men 97-137 mL/min

Question 20

Describe the renin angiotensin arterial system relating to blood pressure

Answer 20

1. Sodium concentration is too low in the distal tubule
2. This causes macula dense cells to become active they signal to the juxtaglomerular cells which release renin into the blood stream
3. Renin is an enzyme
4. Renin passes into the venous blood where it meets the globular protein angiotensinogen which is made by the liver
5. The renin enzymically splits of a decapeptide angiotensin I from the angiotensinogen precursor
6. Angiotensinogen I passes through the lungs and is further cleaved by an endothelial bound ACE into an octapeptide angiotensin II
7. This passes into the artieral blood and in the arterioles it acts on a G protein
8. This activates phospholipase C and increases calcium concentrations which triggers the constriction of the smooth muscle of the systemic arterioles
9. Therefore it increases total peripheral resistance and afterload and therefore assuming there is a constant cardiac output it raises blood pressure

Question 21

How does renin release by sympathetic activation

Answer 21

• Sympathetic activation, this is because there are beta receptors on the juxtaglomerular cells, therefore extra vasoconstriction can be produced by increased amount of renin and angiotensin release

Question 22

How does renal stenosis cause hypertension

Answer 22

• Narrowing of the renal artery can impede blood flow to the target kidney resulting in renovascular hypertension
• Due to local blood flow the kidneys mistake increases in blood pressure of the entire cirucaltory system
• There is a low GFR which is what the creatinine clearance tells us therefore increased production of rennin and increased production of aldosterone as aldosterone increases reabsorption of sodium which leads to hypernatremia and increased blood volume
• Increased renin causes increased angiotensin II which causes increased systemic vasoconstriction and increase ADH release

Question 23

what is the definition of renal artery stenosis

Answer 23

It is the occlusion (narrowing) of the renal arteries)

Question 24

what are the symptoms of renal artery stenosis

Answer 24

• Low creatinine clearance this means that there is a low gfr
• Renovascular hypertension
• High blood urea nitrogen
• Dizziness
• Headaches
• Oedema
• Proteinuria
• Might not get any symptoms except for hypertension, this is only realised when it is tested for

Question 25

what are the risk factors of renal artery stenosis

Answer 25

- Dyslipidaemia - Smoking - Diabetes - Female sex

Question 26

what are the causes of renal artery stenosis

Answer 26

Atherosclerosis - Accounts for 90% of all RAS - This is the build-up of fats and cholesterol and other substances in the artery wall, these harden as they build up - Reduces the diameter of the renal artery - Therefore, it increases total peripheral resistance Fibromuscular dysplasia - Accounts for 10% of all RAS - This is when the muscle in the artery wall grows abnormally - This means that the renal artery can have narrow sections alternating with wider sections giving a beadlike appearance in images of the artery - This condition is more congenital

Question 27

describe how the blood results are caused

Answer 27

170/110 – deterioration in BP control left abdominal bruit – turbulent blood flow usually due to an obstruction hypokalaemia - due to excess aldosterone. Na+/K+ activity increased – so greater loss of K+. Raised blood urea nitrogen – measure of kidney function. High levels of blood urea indicate impaired kidney function. moderate proteinuria – damage to the basement membrane due to chronic high blood pressure kidneys of uneven sizes – ischaemic kidney will be smaller

Question 28

How do you treat RAS

Answer 28

RAS caused by atherosclerosis 1. antihypertensive therapy and lifestyle modification e.g. lower cholesterol and fats diet - statin - antiplatelet agent 2. renal artery stenting and continuation of medical therapy - post stent clopidogrel 3. surgical reconstruction of the renal arteries RAS caused by fibromuscular dysplasia 1. antihypertensive therapy and lifestyle modification - percutaneous renal artery balloon angioplasty 2. surgical reconstruction of the renal arteries - renal artery stenting and dual antiplatelet therapy

Question 29

what medication is used to treat RAS

Answer 29

1. ACE – block the angiotensin converting enzyme and prevent the formation of angiotensin II, e.g. cptorpil 2. Diuretics - Thiazide derivatives – block sodium chloride transporter in the distal tubule - Aldosterone antagonist - Loop diuretics 3. Beta blockers 4. Calcium channel blockers

Question 30

What lifestyle changes are used to treat RAS

Answer 30

1. maintain healthy weight and lose weight if you are overweight 2. eat healthy food 3. limit salt in your diet 4. be physically active 5. reduce stress levels 6. drink alcohol or caffeinated beverages in moderation if at all 7. don’t smoke

Question 31

How is an angioplasty done

Answer 31

- this is when a stent is placed in the artery in order to widen it therefore increasing blood flow and reducing total peripheral resistance 1. a small incision in the thigh is made 2. then they guide a flexible tube called a catheter through the femoral artery into the narrowed renal artery 3. doctor then inflates the surgical balloon which is on the tip of the catheter and this pushes plaque against the inner walls of the artery allowing for better flow 4. stent is placed 5. keeps artery open 6. balloon is then deflated and withdrawn

Question 32

what does the renin- angiotensin aldosterone system do

Answer 32

- increased TPR - increased after load - raises blood pressure cardiac output = BP/TPR

Question 33

how can the sympathetic activation increase blood pressure

Answer 33

Noradrenaline release Increases Renin and Angiotensin release - due to beta receptors on the juxtaglomerular cells

Question 34

what is aldosterone

Answer 34

a mineralocorticoid steroid hormone | - acts on channel protein in the distal convoluted tubule ENac

Question 35

define clearance

Answer 35

this is the volume of plasma completely cleared of a substance per minute

Question 36

what are antihypertensive medication

Answer 36

- interrupt function of RAAS - ACE and ARB ACEi – Captopril, Ramipril SE : Dry Cough ! Increased levels of bradykinin → bronchoconstriction. Also, risk of angioedema. ARB – Losartan or diuretics - stop sodium and water retention - Thiazides- Bendroflumethiazide – block Na/Cl in the DCT - Aldosterone Antagonists – Spironolactone – Potassium Sparing! - Loop Diuretics – Furosemide - Na-K-Cl cotransporter in the thick ascending limb of the loop of Henle

Question 37

why does bradykinin occur with ACE inhibitors

Answer 37

Dry Cough – occurs due to increase in bradykinin which causes bronchoconstriction. ACE is produced in the lungs and will normally break down bradykinin into non active metabolites.

Question 38

what lifestyle modifications can rose make

Answer 38

Improve her diet – reduce salt intake, reduce fatty foods Stop Smoking Exercise More