Working together. Saving lives.

How organs are matched

UNOS provides a vital link in the organ transplant process. Its policies and computerized network match donated organs with transplant candidates in ways that save as many lives as possible and provide transplant recipients with the best possible chance of long-term survival.

The matching criteria developed by the transplant community, and approved by UNOS’ Board of Directors, are programmed into UNOS’ computer matching system. Only medical and logistical factors are used in organ matching. Personal or social characteristics such as celebrity status, income or insurance coverage play no role in transplant priority.

When a transplant hospital accepts a person as a transplant candidate, it enters medical data—information such as the person’s blood type and medical urgency and the location of the transplant hospital—about that candidate into UNOS’ computerized network.

When an organ procurement organization gets consent for an organ donor, it also enters medical data—information such as the donor’s blood type and body size and the location of the donor hospital—into UNOS’ network. Using the combination of donor and candidate information, the UNOS computer system generates a “match run,” a rank-order list of candidates to be offered each organ. This match is unique to each donor and each organ. The candidates who will appear highest in the ranking are those who are in most urgent need of the transplant, and/or those most likely to have the best chance of survival if transplanted.

Prioritizing patients for transplantation

Many factors used to match organs with patients in need are the same for all organs:

The first step

Before an organ is allocated, all transplant candidates on the waiting list that are incompatible with the donor because of blood type, height, weight and other medical factors are automatically screened from any potential matches. Then, UNOS’ computer system determines the order that the other candidates will receive offers.

Geography plays a part

There are 58 local donor service areas and 11 UNOS regions that are used for U.S. organ allocation. Hearts and lungs have less time to be transplanted, so we use a radius from the donor hospital instead of regions when allocating those organs.

The right-sized organ

Proper organ size is critical to a successful transplant, which means that children often respond better to child-sized organs. Although pediatric candidates have their own unique scoring system, children essentially are first in line for other children’s organs.

Factors in organ allocation

Blood type and other medical factors weigh into the allocation of every donated organ, but each organ type has its own individual distribution policy, which reflect factors that are unique to each organ type:

Factors in kidney allocation

kidney

  • Waiting time
  • Donor/recipient immune system compatibility
  • Prior living donor
  • Distance from donor hospital
  • Survival benefit
  • Pediatric status
Factors in lung allocation

lung

  • Survival benefit
  • Medical urgency
  • Waiting time
  • Distance from donor hospital
  • Pediatric status
Factors in liver allocation

liver

  • Medical urgency
  • Distance from donor hospital
  • Pediatric status
Factors in heart allocation

heart

  • Medical urgency
  • Distance from donor hospital
  • Pediatric status
The UNOS Organ Center

The F.M. Kirby Foundation Organ Center

In continuous operation for more than three decades, the F.M. Kirby Foundation Organ Center has been described as the “heart” of UNOS. Like a beating heart, it’s at work continuously—days, nights, weekends, holidays and during inclement weather and even national disasters— saving lives by matching donors with candidates on the transplant waiting list. The primary functions of the Organ Center are to:

  • assist in placing donated organs for transplantation
  • assist in gathering donor information and running the donor/recipient computer matching process
  • assist with transportation of organs and tissues for the purposes of transplantation
  • act as a resource to the transplant community regarding organ-sharing policies
Learn more about the Organ Center

Preserving organs

Donated organs require special methods of preservation to keep them viable between the time of procurement and transplantation. Common maximum organ preservation times include:

kidney
kidney
24-36 hours
pancreas
pancreas
12-18 hours
liver
liver
8-12 hours
heart-lung
heart/lung
4-6 hours
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