Tuesday, May 01, 2007

Matching Kidneys

I was searching teh internets for something to write about and I came across this cool game about living kidney donors from Liberty Science Center. Receiving an organ from a living donor has an 84% success rate, compared to a 54% success rate from deceased donors.

Finding a kidney recipient is a little different then with the other organs. Because the person who needs a kidney can be maintained on dialysis, kidneys are matched not only by blood type but also with with tissue markers, similiar to the way people are matched for bone marrow transplants. This applies to pancreata as well-don't mean to exclude you pancreas people, I'm just trying to keep things simple.

See, if you need a heart, chances are you need one really soon or you're going to die. So you transplant surgeon is going to be looking at the donor's blood type, height and weight. You can't put a linebacker's heart into a petite woman, for example. There are other considerations, obviously, like risk factors and heart function, but if your patient has only days to live, blood type, height and weight are the big three.

Because of dialysis(or insulin therapy for the pancreas), a patient can be maintained until a "perfect" organ becomes available. Actually, there is no "perfect" kidney match. According to my lab director, there are HLA markers that haven't even been discovered yet, they just know they're out there. So, there are six markers that are looked at in matching kidneys and pancreata. If the recipient and the donor share all six, it's called a "zero mismatch". That means they all match, hence NO mismatches. Why don't they just say it's a "six match". Because the HLA never perfectly matches up, due to all the subgroups or something. Dammit Jim, I'm a transplant coordinator, not a biochemist.

Why is this so important? Because an organ with a zero mismatch will last longer and work better. Extending the life of an organ means less chance or rejection, less chance of needing to be retransplanted and less people back on the waiting list. This is why using a living donor is prefered for kidneys. Obviously, only with kidneys, unless you live in China. But that's another post. The easiest way is to find a family member that is compatible. Since you get half your markers from you mom and half from your dad, it is most likely that a sibling will have the same markers as you. 25% chance or matching from a sibling, unless you're identical twins-which is how the first successful kidney transplant was done. But what if you don't have a sibling, let alone an identical twin. What if no one in you're family is a match?

One solution is using a paired donor exchange. Say my daughter needs a kidney but I don't match her. Then say another person needs a kidney and their brother doesn't match him. But his brother matches my daughter and I match with him. We would then donate our kidneys to each other. These programs are usually done at transplant centers and they're being studied, not only for their success rates for also for ethical considerations. Just a few things to think about. Maybe sometime I'll write about the evils of black market kidneys.


Anonymous said...

Very well written Blog that I've enjoyed reading.

I did learn recently that a zero mismatch is not necessarily a six antigen match. example: recipient does not have all six antigens expressed. the remaining five antigens match the donor. it is a zero mismatch but not a six antigen match. I don't know how that affects sharing, paybacks etc. but there is a difference. Keep up the good work my fellow TC

Nurse Mia said...

I recently heard about a case where three mismatched donors traded their family members' kidneys. Pretty remarkable. And how wonderful that they all three had willing donors. I'm not sure my sister would be willing to give me her kidney. She never was one to share toys when we were young. ;-)

geena said...

"Maybe sometime I'll write about the evils of black market kidneys."

Please do! That would be interesting. Not to say that your posts aren't interesting! They are!

You are my favorite transplant coordinator blogger :-)

AzRN said...


we also do live donor livers at my center where we use a lobe of liver from a donor and implant it into the recipient. the transplanted lobe will regenerate in the new host.

we also do a lot of live donor kidneys at my center. if a person can be transplanted with a live donor kidney premptively (before needing dialysis) the better for the recipient's overall health. kidney disease effects many other organ systems as well.

good information!

TC said...

Thanks for the feedback. I have been corrected by an esteemed colleague(you know who you are) that the 5 year success rates for live vs deceased donors are 80% and 67% respectively.

An said...

Hi, your blog was really interesting. I came upon it while doing research on organ harvesting. Thanks for giving me a better understanding about how organs are donated and recipients find a match. Do you know if many people procure organs from developing countries? I wrote this article on China's organ harvesting trade, and found that many westerners have been travelling to China to undergo organ transplants. Its quite scary since, reports have shown that some organs have been harvested from political prisoners. You can check out my article at (Cult)u're Magazine:

A part of me is curious to see how often people from western countries do in fact go abroad for organ transplants.