How does the United Network for Organ Sharing find heart or liver donors for patients?

The obvious obstacle to finding heart and liver donors is the singularity of these organs: a person has only one of each and cannot afford to part with either.

A transplanted kidney, by comparison, can come from a live donor, who has two of them but needs only one to survive. The pool of heart and liver donors is necessarily small, consisting primarily of healthy people who die suddenly in accidents.

To simplify the search for transplantable organs, the National Organ Transplant Act of 1984 established the United Network for Organ Sharing (UNOS). UNOS maintains a data bank of available organs and matches donors and recipients according to location, compatibility and urgency of need.

By law, all transplant centers must be tapped into the network. The law also makes provisions for acquiring organs: all hospitals receiving Medicare funds are required to ask the next of kin of brain-dead patients whether they want the dead relative’s organs donated.

Forty-two states provide organ-donor check-off boxes on their driver’s licenses, but such identification is construed merely as a willingness to donate, and the final decision falls to the deceased person’s relatives.

UNOS maintains local, regional, and national computerized lists of patients awaiting transplants; each patient is ranked according to need and the length of time he has been waiting.

People waiting for new livers, for instance, are rated from 0 to 4: status 0 patients are considered temporarily unsuitable for transplants; status 1 patients are at home and functioning; status 2 patients require continuous medical care; status 3 denotes required hospitalization; and status 4 signifies acute and chronic liver failure. When a liver becomes available for transplantation, the computer scans its lists for compatible recipients.

Final allocation is made based on compatibility, urgency and geography: local status 4 receives top priority, followed by all other local patients; next come regional status 4 patients, then all other regional patients; finally national status 4, and then all other national patients. Local and regional patients have priority over national patients because the transplant must occur as quickly as possible after the organ is removed from the donor.

Ideally, the UNOS system works like this: a person dies, needed organs healthy and intact. The hospital transplant coordinator is called in to talk to the family about organ donation. The family acquiesces.

The organs are examined and the vital information, blood type, tissue type, size, is plugged into the UNOS data bank. The computer, beginning with the local list, scans the patients awaiting transplants. If no match is made locally, the computer jumps to the regional list, and finally to the national list. In 1989, organs were found for slightly better than half of the almost 23,000 people awaiting transplants.

It was in 1989 that surgeons performed the first liver transplant involving a living donor. The procedure allows doctors to replace a child’s ailing liver with a piece of a liver cut from a healthy adult, for compatibility reasons, usually a parent.

So far, surgeons have performed the operation only on children, because they are small and can survive without a full-sized liver. The technique is possible because the liver, alone among human organs, is capable of regenerating: what remains of the donor’s organ will return to normal size after a few months, while the recipient’s organ will grow as the child does.

The operation could make it much easier for children to receive life-saving transplants, more than seven hundred require them each year, but the procedure is potentially very dangerous for the donor, leading some doctors to speculate that cadaver donations will always remain preferable.

Once an organ has been found and transplanted, the recipient faces the hurdle of organ rejection, which occurs when the recipient’s body attacks the new organ as a foreign object. Rejection is very common, it occurs in all cases of heart transplantation, even when the donor and recipient have been closely matched by blood and tissue types.

The only way to treat rejection is by suppressing the recipient’s immune system with steroids, a strategy that can make even a common cold fatal.