Sometimes a donor will want to donate to a recipient, but they’re not compatible, or a good match. This can be due to not having a compatible blood type, antibody levels or other reasons. Some transplant centers will help incompatible pairs of recipient/donors through a process called Kidney Paired Donation, or Paired Exchange, which involves two living donors and two recipients.

If the recipient from one pair is compatible with the donor from the other pair, and vice versa– the transplant center may arrange for a "swap"–for two simultaneous transplants to take place. This allows two transplant recipients to receive living donor kidneys and two donors to still be able to donate, though the original recipient/donor pairs were unable to do so with each other