The kidneys are primarily responsible for ridding the blood of waste. When they fail -- usually because of diseases such as diabetes or hypertension, or because of hereditary conditions -- the damage can extend throughout the body.
Uremia from the buildup of waste products leads to anemia, swelling, difficulty breathing, and ultimately renal failure. Poor kidney function also contributes to other life-threatening conditions, such as atherosclerosis, coronary artery disease, congestive heart failure and stroke.
When both kidneys lose 85-90 percent function, there are only two alternatives: dialysis or transplantation.
Of the two kinds of dialysis, hemodialysis cleans the blood outside the body, and peritoneal dialysis uses a membrane in the abdomen to cleans toxins from the blood. Hemodialysis can be performed only in a clinic or hospital; peritoneal dialysis can be done at home.
Even with diligent compliance, however, a patient on dialysis faces a shortened life span. An ordinary American, age 30-34, can expect to live 50 more years, while a patient on dialysis, of the same age, can expect to live 11 more, according to the U.S. Renal Data System.
For someone receiving a kidney transplant, the life span for that age group increases to 30 years.
"A transplant is not just life-altering, it's truly life-saving," says Shamkant Mulgaonkar, chief of renal and pancreas transplantation for the Saint Barnabas Health Care System. "Someone gave you extra years that no other medical treatment does. That's life-saving."
Fifty-five years ago, a team at the Peter Bent Brigham Hospital in Boston performed the first living kidney transplant, between identical twins. In the decades following, more than 50,000 patients have received kidneys from living donors, most of them blood relatives. The problem, say experts, is finding a willing relative or friend who is also a match in blood type and antibody levels.
In 2000 the first recorded paired kidney exchange, where an incompatible donor-recipient pair swapped kidneys with a second incompatible pair, was performed in Rhode Island.
The first domino chain -- which is set in motion by an altruistic donor and is closed by taking a recipient from the deceased-donor waiting list -- was accomplished in 2005 at Johns Hopkins Medical Center in Baltimore.
A donor chain is slightly different, occurring over time, beginning with an altruistic donor and employing "bridge" donors who sometimes wait weeks or months before a compatible recipient is ready for transplantation. In 2007, an altruistic donor in Michigan started a donor chain that in the past year and a half has resulted in at least 10 transplants across several states.
While the transplants in a domino chain are usually executed simultaneously, or at least within 48 hours, a chain employing bridge donors can theoretically continue forever. Each time a kidney is donated, another one is passed on down the line.
"My dream would be that we eliminate the waiting list," Ohio surgeon Michael Rees told a reporter in March, "because we could turn every altruistic donor into 100 transplants." Rees is the founder of the Alliance for Paired Donation, which generated that first donor chain.