15.8 Kidney Failure

Question 1

What are the causes of kidney failure?

Answer 1

• Damaged structures
(E.g Bowman’s capsule, podocytes, basement membrane)

• Genetics
(E.g polycystic kidney disease)

Question 2

What are the effects of infection/high blood pressure on the kidneys?

Answer 2

• Protein/erythrocytes in urine

(∵ basement membrane/podocytes are DAMAGED from high pressure, no longer act as FILTERS, allow LARGE MOLECULES through to filtrate)

Question 3

What are the effects of kidney failure?

Answer 3

• ￪ UREA concentration (urea cannot be excreted, builds up)
• Imbalanced ELECTROLYTES (excess ions not excreted, leads to osmotic imbalances)
• High BLOOD PRESSURE (excess ions decrease water potential, water moves in, increased hydrostatic pressure)
• WEAKENED BONES (imbalanced calcium + phosphorus)
• PAIN + STIFFNESS (build up of abnormal proteins in blood)
• ANAEMIA (kidneys no longer produce enough erythropoietin, cannot make enough erythrocytes)

Question 4

Why is increased urea concentration an effect of kidney failure?

Answer 4

Urea can no longer be excreted

∴ builds up

Question 5

Why is an imbalance of electrolytes an effect of kidney failure?

Answer 5

Excess ions (K+, Na+, Cl-) cannot be excreted.

leads to osmotic imbalances + eventual death

Question 6

Why is high blood pressure an effect of kidney failure?

Answer 6

Excess ions (which cannot be excreted) decrease water potential of blood

water moves in from surrounding tissue by osmosis

increases hydrostatic pressure of blood

Question 7

Why is weakened bones an effect of kidney failure?

Answer 7

Imbalanced calcium and phosphorus

responsible for healthy bones and teeth

Question 8

Why is pain & stiffness an effect of kidney failure?

Answer 8

Accumulation of abnormal proteins in the blood

which would otherwise be excreted

Question 9

Why is anaemia an effect of kidney failure?

Answer 9

Kidneys are involved in production of erythropoietin,

which makes erythrocytes.

Failed kidneys dont produce enough erythropoietin,

∴ not enough erythrocytes (anaemia)

Question 10

What is the glomerular filtration rate an indicator of?

Answer 10

kidney function

Question 11

How is GFR (glomerular filtration rate) measured?

Answer 11

Indirectly, by measuring creatinine levels

Question 12

What is creatinine and how is it used?

Answer 12

product of muscle breakdown.

Creatinine levels in blood measured to indicate glomerular filtration rate.

(Since usually filtered out of blood by kidneys, an abnormal level of creatinine in the bloodstream indicates insufficient kidney function + possible disease)

Question 13

What must be taken into account when measuring glomerular filtration rate using creatinine?

Answer 13

other factors affecting creatinine levels, e.g age, gender

Question 14

What 2 different treatments are there for kidney failure?

Answer 14

1. DIALYSIS 2. TRANSPLANT

Question 15

What are the 2 types of renal dialysis?

Answer 15

• HAEMODIALYSIS

* PERITONEAL DIALYSIS

Question 16

How does haemodialysis work?

Answer 16

• Blood leaves through artery ⟶ dialysis machine
• Blood + dialysis fluid flow on either side of PARTIALLY PERMEABLE MEMBRANE in COUNTERCURRENT

• DIFFUSION of solutes occurs between blood + dialysis fluid
◦ Urea removed
◦ Salt + mineral ion levels balanced
◦ No net movement of glucose

Question 17

Why is blood thinner added to the blood during haemodialysis?

Answer 17

to prevent blood clotting

Question 18

How are air bubbles removed from the filtered blood during haemodialysis?

Answer 18

blood passes through bubble trap before re-entering patient.

air bubbles in blood can cause heart attack

Question 19

What concentration of urea does dialysis fluid initially contain in relation to the blood?

Answer 19

dialysis fluid initially contains NO UREA

to provide steepest concentration gradient for urea to diffuse out of blood

Question 20

Why does the blood and dialysis fluid travel in a countercurrent during haemodialysis?

In which other topics can a countercurrent be found?

Answer 20

to prevent reaching equilibrium.

(where concentration gradient is no longer steep enough for net diffusion of solutes to occur.)

• Mother’s blood + foetal blood flows in countercurrent in placenta during diffusion of oxygen.
• Solutes in descending + ascending loop of Henle run in countercurrent.
• water and blood flow in fish gills runs in countercurrent
  etc

Question 21

What concentration of salt and mineral ions does dialysis fluid initially contain in relation to the blood?

Answer 21

dialysis fluid initially contains the desired concentration of salt and mineral ions

so that the salt + mineral ion concentration in the blood can be balanced by diffusion

Question 22

What are the advantages and disadvantages of haemodialysis?

Answer 22

• ADVANTAGES
◦ no invasive surgery
◦ no permanent catheter
◦ no immunosuppressants

• DISADVANTAGES
◦ must undergo dialysis @ hospital several times a week for several hours
◦ Must manage diets carefully

Question 23

How does peritoneal dialysis work?

Answer 23

• Dialysis fluid introduced into abdomen using catheter
• DIFFUSION occurs between dialysis fluid + blood across peritoneal membrane.
• Used dialysis fluid enters + stored in bag.

Question 24

What are the advantages and disadvantages to peritoneal dialysis?

Answer 24

ADVANTAGES
• less regulation of diet
• No lengthy hospitalisation

DISADVANTAGES
• must have catheter inserted into abdomen
• peritonitis - infection of the peritoneal membranes

Question 25

What are the advantages and disadvantages to treating kidney failure with a transplant?

Answer 25

ADVANTAGES
• does not disrupt daily life
• lasts many (10) years

DISADVANTAGES
• must wait for DONOR
• risk of REJECTION (minimised by matching antigens using tissue samples, & using immunosuppressants)
• IMMUNOSUPPRESSANTS must be taken daily
• INVASIVE SURGERY - risk of infection