Kidney Failure and Treatment: Dialysis and Transplants — AQA GCSE Biology (Separate)

If the kidneys fail, waste products build up in the blood. Two main treatments are dialysis and transplant.

Why kidney failure is dangerous

If the kidneys stop working, urea and excess ions and water are not removed from the blood. These build up to harmful levels, which can be fatal if untreated.

Dialysis

Dialysis is a machine treatment that filters the blood:

• The patient's blood flows on one side of a partially permeable membrane; dialysis fluid flows on the other.
• The dialysis fluid contains the normal blood concentrations of glucose and useful ions, so only urea and excess substances diffuse out (glucose and useful ions are not lost).

Dialysis must be done regularly (e.g. several times a week, for hours). It controls the condition but is time-consuming, expensive and affects the patient's lifestyle and diet.

Kidney transplant

A transplant replaces the failed kidney with a healthy donor kidney. It allows a normal life, but:

• there is a shortage of donors, and
• the kidney may be rejected by the immune system. To reduce rejection, the donor is matched as closely as possible (tissue type) and the patient takes immunosuppressant drugs.

Evaluating the two treatments

Exam tips

• Explain how dialysis fluid's composition stops glucose and useful ions being lost.
• Transplants risk rejection; reduced by tissue matching and immunosuppressants.
• Be ready to evaluate dialysis vs transplant.