Research Focus: Making the right match for long-term transplant success
While the number of patients waiting for a kidney transplant has risen by 400 per cent over the past 25 years, the number of kidney donors has risen by only four per cent. Unless they have a live donor, Atlantic Canadians in need of a new kidney are waiting more than four years for a suitable organ to become available for transplant. And, many patients require a second and even third kidney transplant over the course of their life, adding more pressure to the limited supply of organs.
Beyond increasing the pool of living donors, optimizing the match between kidney donors and recipients is key. “If we optimize donor-recipient matching, we can maximize the longevity of the transplant and minimize the need for repeat transplants,” says Dr. Amanda Vinson, an NSHA nephrologist and leading researcher in donor recipient pairing.
“This way, we can make the best use of a precious resource.”
Matching for sex—A kidney from a female donor may be too small for a male recipient — but there’s more to sex-matching kidneys than size. Dr. Vinson has received more than $70,000 from the NSHA Research Fund and the University Internal Medicine Research Fund to learn why women appear to have worse outcomes when they receive transplant kidneys from male rather than female donors.
“We’re not entirely sure why this happens, but the theory is that women may make antibodies to the Y chromosome on male kidneys when they are pregnant with a boy,” Dr. Vinson explains. “This could lead to higher rates of rejection when women with pretransplant sons receive kidneys from male donors. We want to learn more about the mechanisms and how we might prevent this organ rejection.”
Matching for size—Dr. Vinson has captured international attention for her work on the importance of matching donors and recipients by size. “If a sexmismatched donor is 30 kilograms smaller than the recipient, the risk of graft failure is about the same as if the donor had diabetes, even if the transplant kidney is healthy,” notes Dr. Vinson. “In other words, the donor recipient mismatch increases the risk of graft failure by 50 per cent. If the donor and recipient are mismatched by size alone, the risk of rejection is increased by 20 per cent.”
Matching for age—As Dr. Vinson notes, it is not necessary or even desirable for a 70-year-old to receive a 20-year old kidney. “An older patient can safely receive an older kidney,” she says. “Age-matching donors and recipients allows us to reserve younger organs for younger patients, who may get more years out of their kidney transplant. This reduces the need for repeat transplants down the road. Conversely, if we give an older kidney to a young patient, they are more likely to outlive their graft and require another transplant.”
Dr. Vinson and her colleagues are looking into other ways to expand the donor pool by opening up the donor criteria.
One study, for example, examined the feasibility of transplanting hepatitis-C-infected kidneys into donors also infected with hepatitis C.
“We have to be open-minded in how we approach kidney donation,” Dr. Vinson says. “We just need the right organ for the right patient—rather than the perfect organ—to create excellent outcomes for our patients.”
This article was originally published in Research Focus on Nephrology Spring 2019 (PDF)