Treating kidney failureSpec 7.21B
In short
Kidney failure lets waste substances such as urea build up in the blood, and it is treated by kidney dialysis or a kidney transplant. In dialysis, urea and excess ions and water pass from the blood across a partially permeable membrane into dialysis fluid. A donor kidney must be a good tissue match, and drugs prevent rejection.
If the kidneys fail, waste substances such as urea build up in the blood. There are two treatments: kidney dialysis and organ donation (a kidney transplant).
Kidney dialysis
- The patient's blood flows through a dialysis machine, separated from dialysis fluid by a partially permeable membrane.
- Urea and excess ions and water pass out of the blood into the dialysis fluid, which is changed to keep the concentration gradient.
- The dialysis fluid has the same concentration of glucose and ions as healthy blood, so useful substances are not lost.
- The cleaned blood is returned to the patient.
Kidney transplant
A healthy kidney from a donor is placed in the patient. The donor kidney must be a good tissue match, and the patient takes drugs so the immune system does not reject it.
| Dialysis | Transplant | |
|---|---|---|
| Advantage | Available straight away | No regular treatment needed once it works |
| Disadvantage | Takes several hours, several times a week | Few donors, and the kidney may be rejected |
Quick check
Which tube carries urine from the bladder out of the body?
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The urethra.
Where is urea produced and from what?
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In the liver, from the breakdown of excess amino acids.
What happens to glucose in the nephron?
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It is all reabsorbed into the blood.
What does ADH do to the collecting duct? (Higher)
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It makes it more permeable to water, so more water is reabsorbed.
Give one treatment for kidney failure.
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Kidney dialysis or a kidney transplant from a donor.
Written and checked against the Edexcel GCSE Biology (1BI0) specification · Updated October 2026