Kidney transplant: how are donors and recipients matched?

This same time last year, there were over  4,500  adults on the UK active kidney transplant list  waiting for a new kidney. Kidneys are the most commonly donated organ and every year thousands of people donate one of theirs to either a friend, relative or someone they don’t know. A healthy person can live with one kidney, so donating one of them can save someone’s life.

For a successful kidney transplant, donors and recipients must have compatible blood types, but that doesn’t always mean they need to have the same blood type.  Dr David Game, a leading London nephrologist who specialises in chronic kidney diseases and transplantation, gives us an overview of which blood types are compatible and what blood type is the most common and easiest to pair in the UK.

What are the types of kidney transplants?

There are two types of kidney transplants: living donor and deceased donor transplants.

• Living donor transplant: the kidney comes from someone who is still alive. Living donors are usually relatives or friends of the recipient but theyneed not be; strangers can donate too. People can live healthy lives with just one kidney, so someone who has two may decide to donate one to someone who needs it.
• Deceased donor transplant: the kidney can come from someone who has just died. There are two types of deceased donations: donation after brainstem death (DBD) or donation after circulatory death (DCD).

Why would someone need to have a kidney transplant?

A kidney transplant is the best treatment for most patients suffering from  kidney failure. The alternative is  dialysis  or  dying of kidney failure.

Unfortunately, there are times when patients are too ill to have a kidney transplant and others who are too ill for dialysis.

How does a patient or doctor find a kidney donor?

Doctors do not find kidney donors for their patients. Deceased donors’ details are sent to a national database and matched to the most suitable recipient. The transplant team then call the recipient to say that a kidney is available for them.

In living transplantation, it is up to the donor to contact the transplant team. The donor is normally approached by the recipient, or their family, and asked if they would be prepared to donate a kidney. Once the donor contacts the transplant team, tests are arranged to see if the potential donor is suitable.

What must match between a donor and the recipient?

Ideally, blood types should be compatible. This is quite complicated, but in general, a person who has  blood types O  can donate to  anyone  - O is a universal donor. However, someone with blood type A can only donate to someone with blood type A, blood type B to B, and AB to AB. As for the recipient, a person with  blood type O can only receive an O kidney, however, someone with blood type A can receive both an A or O kidney and someone with blood type B can receive both a B or O kidney.

• Paired exchange

In living donation, if the donor and recipient do not match, then a paired exchange can be arranged. This is where another donor and recipient pair are found and the donors then donate to the other recipients. That way, everyone that needs a kidney gets one. In some cases a long “chain” of recipient/donor pairs can be devised so everyone involved gets a compatible transplant. In some cases, direct transplants can be organised despite incompatible blood groups. A special treatment to remove the blood group antibodies from the recipient will then be used in this case.

• Tissue matching requirements

Some people have other tissue matching requirements to ensure compatibility – this is called HLA matching. In addition, from the recipient’s perspective a younger kidney is better than an older kidney, and, if someone is very big then ideally, they should have a kidney from someone of a similar size.

Which blood type is the easiest and most difficult to match?

From the recipient’s perspective, the easiest tissue type to match in the UK is AB. This is because they can receive a kidney of any blood type. However, this group is very uncommon, therefore an AB donor, who can only donate to AB, will find it most difficult to find a match. Although a recipient with blood type O can only receive an O kidney, this is the commonest blood group in the UK and is therefore relatively easy to match, the next is A, then B.

Are there any side effects of donating a kidney?

Donating a kidney is an amazing gift. Living donors are having an operation they don’t need - it is mainly to benefit someone else. The risk of death is quoted as 1 in 5000. Of course, it involves a hospital stay and pain associated with an operation, and in the longer term, there is a small increased risk of high blood pressure and a small increased risk of kidney failure. These are explained in detail during medical consultations.

How long does a donated kidney last?

We always base our predictions on historical data, which on the whole shows an increasing lifespan of transplant kidneys with time. The lifespan will always be influenced by the donor’s age and their medical problems, as well as the medical problems of the recipient.

On average we would expect a living donated kidney to last  over 15 years  and a deceased donor kidney around  10-12 years. Of course, this is an average - some last a lot more and some less.

If you would like to become a kidney donor, register your interest using these forms available from the NHS.

To make an appointment with Dr David Game, visit his Top Doctors profile and check his availability.