Physiology (Renal)

Question 1

What is the volume of renal blood flow?

Answer 1

1000 ml/min = 25% of cardiac output

Question 2

What is the flow equation?

Answer 2

RBF = RPF /1 - Haematocrite

RBF - Renal blood flow
RPF - Renal plasma flow

Question 3

How to calculate renal plasma flow?

Answer 3

• Same formula as clearance
• Using P-Aminohippuric Acid (Excreted)

Question 4

Formula for Renal Plasma Flow?

Answer 4

RBF = RPP/RVR

RPP = Renal perfusion pressure
RVR = Renal vascular resistance

Question 5

What is the tubulo-glomerular feedback?

Answer 5

This is when the renal tubules regulate their own blood flow and therefor the glomerular filtration rate

Question 6

What is GFR?

Answer 6

This measures the rate at which blood is filtered by the kidney.

GFR = Clearance

Question 7

What is clearance?

Answer 7

The volume of plasma that is cleared of substance per unit time (ml/min)

Question 8

Formula for clearance?

Answer 8

Cx = UxV/Px

Cx = Clearance
U = Urinary concentration
V = Urine flow
Px = Plasma concentration

Question 9

What is the substance used to measure clearance?

Answer 9

• Insulin
• Freely filtered
• Not secreted, reabsorbed, metabolised or stored
• Creatinine is a more practical surrogate

Question 10

Draw a graph for renal auto-regulation ?

Answer 10

• RBF regulated between MAP of 80-180mmHg

Question 11

What are the auto-regulatory MAP ranges for different organs?

Answer 11

• Heart - 50-150 mmHg
• Brain - 60-160 mmHg
• Renal - 80-180 mmHg

Question 12

Glucose handling?

Answer 12

Glucose filtration by the kidney is directly proportional to the plasma glucose concentration

Question 13

What is T-Max of glucose?

Answer 13

This is the maximal tubular absorption of glucose at 11 mmol/L and 300mg/min

Question 14

What are the hormones produced by the kidney ?

Answer 14

• Erythropoietin
• 1,25-Di-hydroxycholecalciferol
• Renin

Question 15

What is Erythropoietin?

Answer 15

• Regulates erythropoiesis
• Secreted from glomerular apparatus in response to - Hypoperfusion & Hypoxia
• Its receptor present on the membrane of RBCs
• Causes increased production of RBC
• Deficiency responsible for anaemia in chronic kidney disease

Question 16

What is 1,25-dihydroxycholecalciferol?

Answer 16

• It is responsible for calcium balance
• Enhances calcium absorption from proximal bowel

Question 17

What is Renin?

Answer 17

• Part of the Renin-Angiotensin-Aldosterone system
• Activated by decreased renal perfusion

Question 18

List the acid-base buffers in the body?

Answer 18

• Bicarbonate
• Haemoglobin
• Plasma protein
• Phosphate

Question 19

Formula for calculating anion-gap?

Answer 19

AG = (Na+K) - (Cl+HCO)

Question 20

What is the Davenport diagram?

Answer 20

This shows the relationship between pH, PCO2 and HCO3

• See page 110 of passway for explanation of diagram
• Learn how to draw the diagram

Question 21

Correction of bicarbonate deficiency ?

Answer 21

NaHCO3 = BD x 30% x Body weight

BD = Base deficit

Question 22

Base deficit abnormalities?

Answer 22

• Respiratory = HCO normal
• Metabolic = PCO2 normal

Question 23

Sodium handling ?

Answer 23

• ADH has a significant effect on final conc of urinary Na
• Urine is hypotonic after passing through AL thick - Na 100mmol/L
• With ADH - DCT & CD retain water + Increase urinary Na

Question 24

How to calculate serum osmolarity?

Answer 24

2Na + Glu/18 + BUN/2.8

Na - mEq/L
Glu & BUN - mg/dL

Question 25

What are the causes of hypernatraemia ?

Answer 25

- Increased sodium concentration - water depletion -

Question 25

What are the causes of hypernatraemia ?

Answer 25

- Increased sodium concentration - water depletion -

Question 26

What are the causes of hyponatraemia?

Answer 26

- Sodium deficiency - Hyperaldosteronism - Hypotonic saline - TURP syndrome - Reduced water excretion - Hyperglycaemia

Question 27

How is diabetes insipidus treated ?

Answer 27

Desmopressin

Question 28

Effect of rapid correction of hyponatraemia?

Answer 28

Central demyelinating lesion

Question 29

Potassium handling in the kidney?

Answer 29

- Usually maintained between 5-10mmol/L - Horizontal - Potassium secreted in the DCT-Electrochemical gradient

Question 30

Factors affecting inter-compartmental potassium shift?

Answer 30

- Extracellular pH - Circulating insulin - Hypothermia

Question 31

What are the factors causing extracellular shift of potassium?

Answer 31

- Acidosis - Decreased insulin - Beta-blocker - Increased plasma osmolality - Hyperthermia

Question 32

What are the factors causing intracellular shift of potassium?

Answer 32

- Decreased plasma osmolality - Beta receptor activation - Hypothermia - Alkalosis - Insulin

Question 33

What are the effects of hyperkalaemia ?

Answer 33

- Muscle weakness - Nausea & vomiting - Diarrhoea - Palpitation - CVS collapse

Question 34

What are the characteristic ECG changes in hyperkalaemia?

Answer 34

- Peaked t-waves - Wide QRS - Prolonged PR interval - P-wave loss - ST depression - VF / Asystole

Question 35

What is the treatment of hyperkalaemia?

Answer 35

- Treat the precipitating cause - Calcium chloride - 10ml / 10% - Potassium antagonist - Insulin/dextrose over 30 mins - Salbutamol - Dialysis

Question 36

What are the causes of hypokalaemia ?

Answer 36

- Reduced intake - Increase loss (Renal, burns & GI) - Inter-compartmental shift

Question 37

What are the effects of hypokalaemia ?

Answer 37

- Decreased myocardial contractility - Muscle weakness - Polyuria - Ileus

Question 38

What are the characteristic ECG changes of hypokalaemia ?

Answer 38

- T-wave flattening & inversion - U-waves and ST depression - Prolonged QT interval and asystole

Question 39

Treatment of hypokalaemia ?

Answer 39

- Treat the cause - Potassium replacement

Question 40

Properties of calcium ?

Answer 40

- About 98% present in bones - About 40% bound to albumin - Range in plasma between 2-2.6mmol/L

Question 41

What are the hormones regulating calcium levels ?

Answer 41

Read about it ****

Question 42

Hormones enhancing absorption of Calcium?

Answer 42

- Calcitriol - 1,25-Dihydroxyvitamin D - PTH - Regulated

Question 43

Hypercalaemia?

Answer 43

- Present in 98% of cancers - Hyper-parathyroidism - Paget's disease