15.8 - Kidney Failure

Question 1

What are the general causes of kidney failure?

Answer 1

• Kidney infection
  
  • Podocyte structure or tubules damaged
• Raised blood pressure = damages epithelial cells in basement membrane of Bowman’s Capsule
• Genetic Conditions:
  
  • Polycystic kidney disease: Healthy kidney tissue is replaced by fluid-filled cysts or damaged by pressure from cysts

Question 2

What are the effects of high blood pressure on the kidney?

Answer 2

Basement membrane podocytes damaged = protein is in the urine as the damaged structures are not filtering blood

Blood in urine - showing lack of filtration

Question 3

Complete kidney failure results in excess urea and mineral ion build up - what is the effect of this on the body?

Answer 3

• Electrolyte balance loss - body cannot excrete excess ions causing osmotic imbalance in tissues leading to eventual death
• Toxic urea build up - body cannot rid urea, causes poisoning in cells
• High BP - if kidneys fail, osmoregulation fails, blood pressure increases leading to heart problems and strokes
• Calcium/phosphate balance in bones is lost = bones are weakened
• Stiffness in joints due to abnormal protein build up in the blood
• Anaemia - the kidneys produce erythropoietin stimulating erythrocyte formation. If kidneys fail, fewer erythrocytes are produced, more tired

Question 4

What is haemodialysis and how does it work?

Answer 4

Haemodialysis involves the use of dialysis machine, typically carried out in hospital, however some patients conduct this at home

The process lasts 8 hours.

1. Blood leaves 1 artery and flows into the dialyser (dialysis machine)
2. The blood flows between a partially permeable membrane mimicking the basement membrane of the Bowman’s Capsule
3. In the dialyser, there is dialysate (dialysis fluid) – which contains pure water, salts such as bicarbonate of soda and sodium and glucose, as close to the composition of normal blood plasma as possible -, that runs side by side with the blood
4. There is no urea in the dialysate to ensure the steepest concentration gradient to remove all urea from the blood
5. Any excess mineral ions will diffuse out of the blood
6. The blood and the dialysate run counter current to maximise substance exchange
7. There is a constant supply of fresh dialysate to remove as much of the excess substances form the blood as possible, it is removed via a separate path (see diagram
8. The ‘clean’ blood travels to a bubble trap to stop any bubbles from entering you blood
9. If any bubbles enter a patient’s bloodstream, an air/gas embolism can occur. It causes blockages in blood vessels which can lead to heart attacks, strokes or respiratory failure.
10. The blood is then returned to a vein in the arm.

Question 5

What must the patient control during haemodialysis?

What process does haemodialysis rely on?

Answer 5

Must be managed carefully, must eat little protein and salt to maintain blood chemistry

No active transport occurs during haemodialysis, it relies solely on diffusion down a concentration gradient.

Question 6

What is the peritoneum?

Answer 6

Peritoneum: Natural dialysis membrane formed by the lining of the abdomen

Question 7

What is peritoneal dialysis?

Answer 7

Dialysis done in the body.

This type of dialysis can be done at home.

The process takes several hours, this allows time for the urea and excess mineral ions to pass out the peritoneal membrane and into the dialysate. The fluid is drained and discarded, leaving the blood balanced and urea/excess mineral ions removed.

Question 8

What are the benefits of a kidney transplant?

Answer 8

Long term dialysis brings side effects.

Transplant is the best long term solution. A new healthy kidney from a donor has its ureter and blood vessels joined at the bladder.

Question 9

What are the issues with having a kidney transplant?

Answer 9

Risk of rejection

Organ donor kidney antigens differ from the antigens of the patient, so the immune system may reject and destroy the kidney

Question 10

How can the risk of rejection when having a kidney transplant be reduced?

Answer 10

• To reduce the risk of rejection
• The organ donor should have the same tissue type and blood group
• Patient given immunosuppressant drugs for the rest of their lives preventing rejection
• Issue with using immunosuppressant drugs
• Patients will not effectively respond to infections
• Transplanted kidneys last 9-10 years, once the organ fails the patient must return to dialysis and then try to find a new donor.

Question 11

What are the pros and cons to dialysis and transplant?

Answer 11

• Dialysis is readily available than organ donors
  
  • But patients must monitor their diet carefully and it is more expensive in the long run compared to using a transplant
• Using a transplant means none of the dietary restrictions
  
  • However there is a shortage of donors, donors are usually people who die of stroke, heart attack or road accidents. And many people do not sign up as donors