November 2009

by George Taniwaki

The short answer is yes. The long answer is complex and interesting. (Well, it’s interesting if you are a statistics geek like me.)

First, some good news. Most of the available data indicates that live kidney donors lead long healthy lives. Studies show that they live longer than the general population. For instance, see Transpl. Oct 1997 and New Engl. J. Med. Jan 2009. This is not an unexpected result and does not mean that donating a kidney will lengthen your life. Instead, it is probably a result of the fact that kidney donors are screened for good health (called selection bias) and are healthier than the general population, and thus more likely to live longer.


Survival rate of kidney donors is similar to general population. Image from New Engl J Med

A more meaningful comparison would be to look at longevity of kidney donors compared to a stratified sample of the general population controlled for age, income, gender, geography, medical history, and access to health care (or health insurance). Such a study would be difficult to conduct. That’s because neither hospitals nor the United Network for Organ Sharing (UNOS) do a good job of tracking kidney donors after surgery. They do a better job of tracking recipients. So the data on the long-term outcomes of donors is sparse.

Donating a kidney does expose donors to several near-term risks that may shorten their lives. A study in J. Amer. Med. Assoc. Mar 2010 shows that in the 90 days after a donation, the mortality rate was 3.1 per 10,000 for donors compared to 0.4 per 10,000 for a control group. A good summary of these risks is provided by the Mayo Clinic and by the National Kidney Foundation. Actual risks may vary and donors should discuss them with the transplant surgeon. However, the risks are small, especially when compared to the great benefits that will be experienced by the recipients. Not all researchers are quite as sanguine. A note in Clinical J. Amer. Soc. Nephr. Jul 2006 cautions that more studies are needed.

For the long-term, the risk of premature death are low. The same JAMA study cited above shows the long-term survival is excellent. The risk of death was the same or lower than for the control group after five years (0.4% vs. 0.9%) and after 12 years (1.5% vs. 2.9%), respectively.

There is one risk that is correlated with kidney donation that is very odd and deserves additional investigation by epidemiologists. Specifically, it appears that kidney donors are more likely than the general population to develop end stage renal disease (ESRD). My friend, Ken Klima at Hebert Research, heard this surprising finding in a UWTV lecture entitled Understanding a Chronic Killer: Kidney Disease, Part 1 (additional kidney related videos are also available). The data is reported in a rather shocking manner by Wendell Fleet a professor of nephrology at the UWMC, which is where I am expecting to have my surgery. At 34:40 into the video, he says:

“If you donate one of your kidneys to a loved one, or in a fit of philanthropic zeal to a total stranger (audience laughs), you may wear out your kidney. We initially told people you only need one, ‘give it up and save someone’s life.’ So we followed those people and in a few of them the creatinine levels inch up. A few have required renal replacement therapy. They wore out their remaining kidney. On the positive side, you go directly to the top of the list for a transplant yourself if you give someone a kidney (audience laughs).”

Dr. Fleet may be referring to data from various studies, such as one reported in Transpl. Nov 2002 or Transpl. Proc. June 2008 (subscription required), that show that among patients undergoing living donor nephrectomies, about 0.35% developed ESRD compared to 0.25% for the general population. Although this is a difference of only 0.10%, it represents a huge increase of 40% (=0.10/0.25). Am I putting myself at risk for kidney disease by donating my kidney?

I don’t think so. I have a guess as to what’s really happening. Susceptibility to kidney disease is partially hereditary, as are other chronic conditions like diabetes and hypertension that are correlated with ESRD. Since historically a majority of kidney donors are family members of the recipient, they may have also inherited the genes that cause ESRD. A similar conclusion is stated in an editorial in the Nephr. Dialy. Transpl. May 2003. Again, a more complete analysis would compare rates of ESRD correcting for age, income, gender, geography, access to medical care, and medical history (especially a family history of ESRD).

For more information on becoming a kidney donor, see my Kidney donor guide.

[Update1: I added a link to a study that questions the low medical risks reported for live kidney donors.]

[Update2: I added a link to a new JAMA study.]

[Update3: An Aug 2010 blog post contains additional findings on the safety of kidney donation.]

The United Network for Organ Sharing UNOS), announced on Nov 17 that it has approved 236 living donor kidney programs. All of these programs had previously been approved by the UNOS for their deceased donor kidney transplant programs. The Univ Washington Medical Center, where I expect my surgery will take place, is among the hospitals that has been approved to conduct a living donor program. A complete list of transplant centers is available here.

Currently, the UNOS is only responsible for the allocation of organs from deceased donors. It does not administer the allocation of organs from live donors. The UNOS is developing a national system for allocating unmatched paired donations and began a pilot program in September. It expects to roll out the program to all transplant centers by the end of 2010. Donor chains and stranger donations (directed and nondirected) are not currently included in this system. I’ll do additional research to see how the UNOS’s plan may affect the work being done by the groups currently working with living donors, such as the National Kidney Registry and the Alliance for Paired Donation.

[Update2: The UNOS conducted its first match run in Oct 2010.]

[Update1:  Replaced the term cadaver with deceased donor.]

Happy Thanksgiving! It’s good to be home in Denver for the holidays.
Yesterday marked my second year waiting to become a kidney donor. During that time I’ve learned a lot about the process of donating a kidney, the multitude of rules used to allocate organs, the ethical controversies regarding live donors, and possible solutions (technical, legal, and social) to the shortage of transplantable organs. I hope to cover all of these issues in my blog.

I just received an email from Laurie Reece, the executive director of the Alliance for Paired Donation. The current issue of People magazine has dedicated five pages (which is a lot) to cover the story of a live kidney donor chain that started in 2007, has involved 21 people so far, and is still continuing. (This particular donor chain is also mentioned in a Sep 2009 blog post when it was ten people long.) This is the kind of favorable publicity that may encourage many more people to be live kidney donors.


Unmatched pairs and their exchange partners. Photo from People

As Ms. Reece says in her email:

People magazine, one of the most widely read periodicals in the country, includes a story and photos this week about the groundbreaking approach to increasing the quantity and quality of kidney transplants through non-simultaneous extended altruistic donor (NEAD) chains pioneered by the Alliance for Paired Donation.

“The 5-page feature includes photos and interviews of donors and recipients involved in the world’s first and longest chain of kidney transplants made possible by maximizing the good that can come from an altruistic, or Good Samaritan, kidney donor. The chain was coordinated through Alliance for Paired Donation from July 2007 to March 2008. The donor at the end of the chain continues to wait for her chance to continue the chain. 

“People’s assistant editor, Lorenzo Benet and camera crew spent a weekend in October at the University of Toledo meeting, interviewing and photographing the kidney chain participants. The magazine has a weekly circulation of 3.75 million – and this week’s issue also happens to feature the “Sexiest Man Alive” contest winner, so newsstand sales should be brisk.“

[Update1: I sent an email to Ms Reece telling her that I mentioned the People article in my blog. Below is part of her response:

“We’re getting about three times the Web traffic we normally do, so the People story is making an impact, […] one we hope we can keep up with.” ]

[Update2: Another long kidney donor chain is featured in Glamour magazine (see Feb 2010 blog post).]

I wanted to add a few additional citations to my recent blog post on my split renogram. So I ran a search using the phrase “split renogram ct scan”. Guess what comes up as the top result in Google?


For some reason, my blog post is the top item. Perhaps it is due to its newness and will move down over time. People pay lots of money to have consultants manipulate their web pages so that they appear at the top of search engine results, a process called search engine optimization.

Compare the above list to the results using Bing. Notice that there is only one item that is common between the lists from these two search engines. That’s why it’s a good idea to use multiple search engines when doing research.


[Update: Both Google and Bing now feature my blog as the top result for a query of “split renogram ct scan”. Pretty cool.]

As I mentioned in my Tuesday blog post, I had my fifth appointment at the Univ Washington Medical Center to have a split renogram test. Afterwards, I ordered a CD with my test results. The CD arrived in the mail today. It consists of the two images shown below. Not as cool as the CT scan, but still definitely worth the price.

The image below shows a series of images of my abdomen over time. The dark spots show the concentration of the MAG3 tracer captured by the gamma camera. The first two rows show 16 images taken one second apart. Notice how quickly the tracer perfuses through the abdomen, and starts to collect in the kidneys. My left kidney is on the left of the image and is higher and larger than the right one.

The last three rows show 20 images taken two minutes apart. Here you can see that within six minutes (third image in third row) nearly all of the MAG3 tracer is already in the kidneys. The tracer begins to be excreted through the ureters and collected in the bladder. By 20 minutes (fourth image in fourth row) nearly all of the tracer has been filtered out by the kidneys and is in the bladder. I’m still amazed how fast and how thoroughly the kidneys remove molecules and ions from the blood.


Image from UWMC

The line chart below compares the filtration rate of the left kidney (red dashes) with the right (green) and the fill rate of the bladder (blue). The peak output of the left kidney is about 30% higher than the peak of the right, but they both peak at the same time and they track closely thereafter. The table on the right shows that my left kidney filtered 56% of the MAG3 while my right kidney filtered 44%. Notice the image in the lower right showing the selection rings the radiologist used to define the location of the left kidney, right kidney, and bladder.


Image from UWMC

[Update: The UWMC transplant coordinator and I spoke on Nov 16. My split renogram test result is inconclusive, so the surgeon wants to consult with the radiologist before deciding which kidney to remove.]

by George Taniwaki

As described in an earlier post, my CT scan angiogram shows that my left kidney is larger than the right one. A bit of research on the web shows this is a common occurrence, though I can’t find any data on what proportion of the population has this asymmetry. In severe cases where the smaller kidney does not function correctly, the condition is called unilateral renal hypoplasia, but again, I cannot find an incidence rate. (I do find reference to having only one kidney, called unilateral renal agenesis, and it is estimated to occur in 0.10% to 0.25% of births.)

In transplant surgeries, the larger kidney will remain in the donor (I guess a corollary of “do no harm” is minimize the chance of harm) while the smaller kidney is removed and implanted in the recipient. Immediately after the transplant, the one good kidney in both patients begins to work harder and increases in size to allow greater blood flow. Eventually, each kidney alone should provide about 70 to 80% of the capacity of the original two kidneys. This is more than adequate to live a normal life.

However, in my case, the difference in size between my kidneys is large enough that the surgeon and nephrologist would like to run a test to ensure that my smaller kidney has enough capacity to support the full needs of the recipient on its own. If it doesn’t, I won’t be allowed to donate.

What is it? Split renogram using gamma camera
Why is it needed? Ensures that the smaller kidney has enough capacity for the patient when transplanted
How is it done? A tracer is added to your blood and then a camera records how much flows through each kidney
Preparation None
Test time One hour
Risks None. The amount of radiation used is very small
Discomfort You have to unbutton your pants. You have to stay very still during the 40 minutes the test takes. The test is not painful


I arrive at UWMC today for my fifth hospital appointment. I am to undergo a procedure called a split renal function test, or a split renogram. First, I empty my bladder. Then I drink two cups of water and am given a small dose of radioactive tracer through an intravenous bag fed into my right arm. The tracer, called Tc-MAG3 (which stands for mercapto-acetyl-triglycine chelated with technetium 99, for those who are curious), will be filtered out by the kidney and thus be concentrated there and in my bladder. Technetium 99 has a half-life of only 6 hours, meaning I should not be exposed to too much radiation. Technetium 99 emits low-energy gamma rays that are detected though the use of a gamma camera.

After letting the IV flow for about a minute the operator positions the camera above my abdomen and tells me to lay still for 40 minutes. The camera takes a series of images at a rate of one per second to record the concentration of MAG3 within my abdominal cavity. Apparently, the images taken by the gamma camera will give a more detailed estimate of split kidney function than a CT scan can. (However, I found some articles that say CT scans alone can estimate split kidney function and the results match gamma camera estimates with r>0.9.)


I prepare for the split renogram with an IV in my right arm and my abdomen under the gamma camera. Photo by UWMC staff

After the procedure, I ask the operator if I can get the images on CD. She says yes, but unlike the CT scan, there is a post-processing step involved. A radiologist must select the regions of the image that denote the left kidney, right kidney, and bladder so that the software can calculate the filtration rate. I go to the cashier and pay my $13.50 fee for the CD. But I won’t be able to take the CD home with me, they will need to mail it.

For more information on becoming a kidney donor, see my Kidney donor guide.

[Update1: The CD arrives in the mail on Friday. Blog post here.]

[Update2: Added a summary table.]