BOSTON — A process meant to equitably allocate human livers for transplant is flawed, medical experts say, costing lives among those most in need and putting relatively healthy patients at risk.

Studies presented this week at the American Transplant Congress reveal that U.S. surgeons are transplanting livers into their own patients first, even when those patients are not as sick as others.

Officials say the federal regulation governing transplant eligibility should be changed so that organs go to the sickest patients first. That is not always the case, even though the rule, imposed in February 2002, ranks patients based on the severity of their disease.

The rule came about because of widespread allegations that doctors were bending the rules in favor of their own patients, including putting them in hospital intensive care units and on transplant waiting lists long before they needed the surgery.

Studies presented at the international scientific meeting indicate that the rules are still being bent.

Today, when a liver suitable for transplant is identified, local Status One patients are considered first. Status One patients are those who are near death.

If no Status One patients are in the local area or if the organ is not a biological match, the search for a recipient then expands to the organ transplant region, which can include several states.

If no Status One patient in the region is a match, the transplant surgeons in the city where the liver was recovered can give the organ to the patient ranked highest by the disease severity score, known as the Model for End-stage Liver Disease.

The problem, researchers say, is that even by following these steps, surgeons are still allowed to send too many livers to patients who rank the lowest.

Ironically, the practice puts patients who are relatively healthy at a higher risk of death, the researchers say. Surgeons have developed an expanded criteria to accept livers for the sickest patients, believing that a marginal liver is better than no liver.

But transplanting a liver considered medically marginal into a person who is not critically ill puts that patient in greater danger of death from complications, infections or organ rejection, the researchers say. They say nearly 30 percent of the patients ranked with the least severe disease are receiving marginal livers.

At the same time, sicker patients are dying. "Our focus has to be on what's best for the patient," says Robert Merion, professor of surgery at the University of Michigan. "There may be somebody right across the river who doesn't have access to that organ." Merion is clinical transplant director for the Scientific Registry of Transplant Recipients, a federally funded database of transplant outcomes.

Officials are considering changes in the transplant system regulated by the United Network for Organ Sharing that would ensure that organs go only to patients who rank high on the disease severity scale.

"We need to ensure that people who need the livers the most are getting them," says Clive Callender, who heads the transplant program at Howard University in Washington, D.C. "As we get more information, we change our policies. When you shine a light on things, people change their behavior."