Kidney transplantation · Before the transplant
Someone is willing to give you a kidney. It just does not fit.
Paired exchange solves this by swapping donors between families. Almost every patient with a willing but incompatible donor can be transplanted this way — and the chains can run seven pairs deep.
The short answer
- If your donor is willing but incompatible, their kidney can go to another patient — and that patient's donor gives to you.
- Both transplants are then fully compatible. No special preparation, no antibody removal.
- It works for blood type mismatch and for pairs blocked by a positive crossmatch.
- Exchanges are not limited to two pairs. Chains of seven have been performed.
- In Türkiye, cross-transplants can be arranged between any two transplant centres, with mutual consent, without going before a commission.
The problem it solves
A husband wants to give his wife a kidney. A daughter wants to give her father one. They are willing, healthy, and ready — and then the tests come back and the pair does not match.
Two things commonly cause this:
- Blood type incompatibility — the donor's group cannot go to the recipient's.
- Antibodies in the recipient's blood — a positive crossmatch against that particular donor.
In both cases the kidney is good. It is simply pointed at the wrong person.
If two families are stuck in the same way, swap the donors. Your donor gives to their patient; their donor gives to you. Both transplants are compatible, and two operations replace two dead ends.
How the exchange is arranged
Pairs who cannot proceed with their own relative are entered into cross-transplant lists. Matching is not done on blood type alone — the centre also weighs tissue compatibility, age, and underlying diseases when pairing families.
A simple two-way exchange
The most common form. Take a recipient with blood type A whose willing donor is type B, and another pair in the mirror position:
| Donor | Recipient | Gives kidney to | |
|---|---|---|---|
| Pair 1 | Type B | Type A | Recipient of Pair 2 |
| Pair 2 | Type A | Type B | Recipient of Pair 1 |
Two incompatible pairs become two compatible transplants. Patients with blood type A or B who have no compatible donor of their own are natural candidates for this.
Three-way exchanges, and why an O donor is valuable
Exchanges are not limited to pairs. Consider a family whose donor is blood type O and whose recipient is A or B — compatible on blood type, but blocked because of antibodies in the recipient's blood.
That pair can enter a three-way exchange. Because a type O kidney can go to any recipient, their donor unlocks the chain — and in doing so makes transplantation possible not only for themselves but for two other families whose blood types did not match.
This is why a willing O donor is disproportionately useful, even when their own pair seems stuck.
Domino chains
With enough pairs, exchanges become chains. Each donor gives to the next recipient in line, and one chain can transplant many patients in a single coordinated operation.
Because the number of possible arrangements grows with every pair added, this is the single largest practical answer to organ shortage available today.
The first seven-pair domino cross transplantation performed anywhere outside the American continent was carried out by our team.
How the surgery is handled
In a cross transplant, the operations do not happen one after another. The recipient's and the donor's surgeries begin at the same time, and the kidneys are removed and transplanted simultaneously.
This is deliberate. It removes any possibility that one family proceeds and another is left behind after their donor has already given — a fairness problem that simultaneous surgery eliminates by design.
The legal position in Türkiye
Cross-transplantation is governed by the Organ and Tissue Transplantation Services Regulation, published in the Official Gazette of 1 June 2000, number 24066.
Under that regulation, living donation is permitted from:
- The recipient's spouse, where the couple has actually lived together for at least two years
- Blood and in-law relatives up to the fourth degree, fourth degree included
Cross-transplants can be performed between patients registered at any two transplant centres, by mutual consent, without applying to the ethics commission.
This matters practically: your centre does not need to hold both pairs. If a matching pair exists at another centre, the exchange can be arranged directly.
Questions worth asking
- Is my pair on a cross-transplant list? Being told "you are incompatible" is not the same as being entered into an exchange programme.
- Which lists does this centre have access to? A larger pool means a faster match.
- Has a three-way or chain arrangement been considered, not only a direct swap?
Prof. Dr. Murat Tuncer
Nephrologist and transplant physician. His team performed the first seven-pair domino cross transplantation outside the American continent, and introduced ABO-incompatible kidney transplantation to Türkiye. Author of Kidney Transplantation — With Questions and Answers (Istanbul, 2020).
Send us both blood types and the crossmatch result
Yours and your donor's. We will tell you whether a paired exchange is realistic in your case, and what it would involve.
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. Regulations governing living donation and paired exchange differ between countries and change over time. Always consult your own nephrologist or transplant centre before making decisions about your treatment.
References
- Organ ve Doku Nakli Hizmetleri Yönetmeliği. Resmî Gazete, 1 June 2000, no. 24066.
- Tuncer M, et al. ABO-incompatible kidney transplantation: first cases in Türkiye. Transplant Proc 2012;44(6):1703–5.
- Knoll G, Cockfield S, Blydt-Hansen T, et al. Canadian Society of Transplantation consensus guidelines on eligibility for kidney transplantation. CMAJ 2005;173(10).
