An altruistic donor is a person that wishes to donate a kidney but who has no intended recipients; they simply want to donate to someone who can benefit from a transplant. Other terms used to describe altruistic donors include "non-directed" or "Good Samaritan" donors.
Altruistic donors are a huge part of the success of Kidney Paired Donation transplants because they add a donor but not a recipient into a registry, thereby increasing the donor pool.
Many Kidney Paired Donation transplant chains start with an altruistic donor, and after the first round of transplants, the incompatible family member or friend of one of the recipients of the first round of transplants then acts as the bridge donor that initiates the next set of transplants (graphic below shows how an altruistic donor kicked off a chain of transplants, which left a bridge donor to initiate another chain of transplants).
Alternatively, the remaining donor may also donate to someone waiting on the deceased donor list, and the chain ends at that time.
By kicking off donor chains such as the one above, an altruistic donor has the opportunity to help numerous patients, since without the altruistic donor, the patient may not have received a transplant.
Read the blog of an altruistic kidney donor.