Kidney transplantation · Before the transplant
Your donor's blood type does not match. Now what?
This is where many families are told the conversation ends. It does not have to — there are two established routes around an incompatible blood type, and both are in use today.
The short answer
- Blood type compatibility is more important than tissue matching — but it is no longer an absolute wall.
- Rh factor does not matter. A negative donor can give to a positive recipient and the reverse. This is the single most common misunderstanding.
- Blood type O donors can donate to anyone.
- Where blood types are incompatible, two routes exist: ABO-incompatible transplantation and paired exchange.
- ABO-incompatible transplantation is real but not routine — it is costly, not available in every centre, and reserved for selected patients.
First, the part that is fixed
There are four blood types: A, B, AB and O. Which one you have depends on whether you carry two proteins called the A and B antigens. Carry A, and your type is A. Carry both, and it is AB. Carry neither, and it is O.
These antigens do not sit only on red blood cells — they are on the surface of all known body cells, acting as an identity card. This is how the immune system tells what belongs to the body from what does not, and it is why blood type carries so much weight in transplantation.
| If your blood type is | You can receive a kidney from |
|---|---|
| O | O only |
| A | A or O |
| B | B or O |
| AB | Any group — O, A, B or AB |
Read the table the other way and one thing stands out: a donor with blood type O can donate to anyone. That makes O donors valuable, and it also explains why patients with blood type O wait longest — they can give to everyone but receive only from their own group.
My blood type is A Rh negative, my wife's is A Rh positive. Can I donate?
Yes, easily. The Rh factor — the plus or minus after your blood type — does not matter in kidney transplantation.
A person who is A negative can donate to a recipient who is A negative or A positive. In the same way, both B negative and B positive patients are called for an organ from a B positive deceased donor.
This question comes up constantly, and a surprising number of willing donors have been turned away over it by people who should have known better. If Rh was the stated reason in your case, ask again.
When the blood types genuinely do not match
In theory, transplantation without blood group compatibility is not possible. The antigens that mark the donor's cells would be read by the recipient's immune system as foreign, and attacked.
Theory and practice, however, often part company. The task of medicine is to reach what looks impossible when a patient's life depends on it — and in Japan, the United States and Norway, a limited number of transplants between blood-group-incompatible pairs began to be performed.
The aim is to introduce the donor's blood type antigen to the recipient as though it were their own. Using filters similar to those in dialysis, the antibodies in the recipient's body that would treat the donor kidney as an enemy are removed.
Much as dialysis cleans toxic substances from the blood, the process is repeated several times. After that, transplantation may become possible.
Can this be done for every patient?
No — and it is important to say so plainly. ABO-incompatible transplantation is not a method that can be applied widely, or in every centre.
- Outcomes are somewhat lower. Ten-year survival of the transplanted kidney is around 10% below that of blood-type-compatible transplants.
- It is expensive. The specialised filters used are costly, and several are needed for a single transplant. Reimbursement varies by country and changes over time.
- It requires an experienced centre. The preparation protocol is demanding and not every transplant unit performs it.
For these reasons it is currently reserved for patients who have no realistic dialysis option — because of vascular problems or previous peritonitis — or who cannot tolerate dialysis psychologically in any way.
ABO-incompatible transplantation is not an alternative to deceased donor transplantation, and it should not be presented as one. It was introduced as a solution for patients who had run out of other options. The wider goal remains increasing the number of transplants from deceased donors.
Is there another way around an incompatible pair?
Yes, and it is often the better first question: paired exchange.
If you and your donor are incompatible, and another pair is in the same position, the two donors can be swapped — your donor gives to the other recipient, and theirs gives to you. Both transplants are blood-type compatible, and neither patient needs the preparation described above.
Exchanges can involve two pairs, or chains of several. A donor with blood type O is particularly valuable in these arrangements, for the reason given earlier.
Where this leaves you
If you have been told that your donor's blood type rules out a transplant, there are three questions worth putting to your centre, in this order:
- Was it really the blood type, or the Rh factor? If Rh, the objection does not stand.
- Has paired exchange been considered? It requires no special preparation and produces a fully compatible transplant.
- Is ABO-incompatible transplantation available here? If not in your centre, it may be available in another.
None of these guarantee an answer. But "the blood types do not match" is the beginning of the assessment, not the end of it.
Prof. Dr. Murat Tuncer
Nephrologist and transplant physician. He introduced ABO-incompatible kidney transplantation to Türkiye in 2007 and published the first case series; his team also reported the first ABO-incompatible transplants performed in the country. Author of Kidney Transplantation — With Questions and Answers (Istanbul, 2020).
Send us the blood types — both of them
Your blood type, your donor's, and any assessment you have already been given. We will tell you which of the routes above applies to your case, and which do not.
Medical disclaimer. This article is general information adapted from a published book. It is not personal medical advice, it does not establish a doctor–patient relationship, and it cannot replace assessment by the physician treating you. The availability, cost and reimbursement of ABO-incompatible transplantation differ between countries and centres and change over time. Always consult your own nephrologist or transplant centre before making decisions about your treatment.
References
- Tuncer M, et al. ABO-incompatible kidney transplantation: first cases in Türkiye. Transplant Proc 2012;44(6):1703–5.
- Tuncer M, Gurkan A, Erdogan O, Yucetin L, Demirbas A. Lack of impact of human leukocyte antigen matching in living donor kidney transplantation: experience at Akdeniz University. Transplant Proc 2005;37(7):2969–72.
- Knoll G, Cockfield S, Blydt-Hansen T, et al. Canadian Society of Transplantation consensus guidelines on eligibility for kidney transplantation. CMAJ 2005;173(10).
