填空题 Mike and Adam Hurewitz grew up together on Long Island, in the suburbs of New York City. They were very close, even for brothers. So when Adam's liver started failing, Mike offered to give him half of his. The operation saved Adam's life. But Mike, who went into the hospital in seemingly excellent health, developed a complication—perhaps a blood colt—and died last week. He was 57. Mike Hurewitz's death has prompted a lot of soul searching in the transplant community. Was it a tragic fluke or a sign that transplant surgery has reached some kind of ethical limit? The Mount Sinai Medical Center, the New York City hospital where the complex double operation was performed, has put on hold its adult living donor liver transplant program, pending a review of Hurewitz's death. Mount Sinai has performed about 100 such operations in the past three years.
A 1-in-100 risk of dying may not seem like bad odds, but there's more to this ethical dilemma than a simple ratio. The first and most sacred rule of medicine is to do no harm. "For a normal healthy person a mortality rate 1% is hard to justify," says Dr. John Fung, chief of transplantation at the University of Pittsburgh Medical Center. "If the rate stays at 1%, it's just not going to be accepted." On the other hand, there's an acute shortage of traditional donor organs from people who have died in accidents or suffered fatal heart attacks. If family members fully understand the risks and are willing to proceed, is there any reason to stand in their way? Indeed, a recent survey showed that most people will accept a mortality rate for living organ donors as high as 20%. The odds, thankfully, aren't nearly that bad. For kidney donors, for example, the risk ranges from 1 in 2,500 to 1 in 4,000 for a healthy volunteer. That helps explain why nearly 40% of kidney transplants in the U.S. come from living donors
The operation to transplant a liver, however, is a lot trickier than one to transplant a kidney. Not only is the liver packed with blood vessels, but it also makes lots of proteins that need to be produced in the right ratios for the body to survive. When organs from the recently deceased are used, the surgeon gets to pick which part of the donated liver looks the best and to take as much of it as needed. Assuming all goes well, a healthy liver can grow back whatever portion of the organ is missing, sometimes within a month.
A living-donor transplant works particularly well when an adult donates a modest portion of the liver to a child. Usually only the left lobe of the organ is required, leading to a mortality rate for living-donors in the neighborhood of 1 in 500 to 1 in 1, 000. But when the recipient is another adult, as much as 60% of the donor's liver has to be removed. "There really is very little margin for error," says Dr. Fung. By way of analogy, he suggests, think of a tree. "An adult-to-child living-donor transplant is like cutting off a limb. With an adult-to-adult transplant, you're splitting the trunk in half and trying to keep both halves alive."
Even if a potential donor understand and accepts these risks, that doesn't necessarily mean the operation should proceed. All sorts of subtle pressures can be brought to bear on such a decision, says Dr. Mark Siegler, director of the MacLean for Clinical Medical Ethics at the University of Chicago. "Sometimes the sicker the patient, the greater the pressure and the more willing the donor will be to accept risks." If you feel you can't say no, is your decision truly voluntary? And if not, is it the medical community's responsibility to save you from your own best intentions?
Transplant centers have developed screening programs to ensure that living donors fully understand the nature of their decision. But unexamined, for the most part, is the larger issue of just how much a volunteer should be allowed to sacrifice to save another human being. So far, we seem to be saying some risk is acceptable, although we're still vaguer about where the cutoff should be. There will always be family members like Mike Hurewitz who are heroically prepared to make the ultimate sacrifice for a loved one. What the medical profession and society must decide is if it's appropriate to let them do so.

填空题 Describe in your own words the liver transplant between the two brothers Mike and Adam.

填空题 What is the major issue raised in the article?