Great post, and I’m a little sad that kidney donation has fallen a bit out of EA discussions. I also want to emphasize two things to people who are worried about the health risks from donating their kidney.
As the OP says, you have to have substantially above average kidney functioning in order to be eligible. I recall seeing estimates that because of this screening, living donors are actually at lower risk for kidney disease than the general US population. But I can’t find them so take that with a grain of salt.
Being a living kidney donor sends you to the top of transplant lists, so in the extremely unlikely event that you do have kidney problems, you are far more likely than average to receive a transplant quickly.
you have to have substantially above average kidney functioning in order to be eligible
When I looked into this, I came away with the impression that this is not true. According to the formal requirements, you don’t need to have above average kidney function to be eligible. You need to not have a recorded history of kidney disease and take a test that weakly indicates that you are currently in the healthy range.
The healthy range isn’t tied to your age. A young person with healthy kidney function can expect to probably have reduced kidney function in old age. The cut off for donation is a GFR of 90 (though doctors can accept patients as low as 60 in some cases). If your GFR is 90 and you’re 80 years old, you’ve got great kidney function. If your GFR is 90 and you’re 30, you don’t have to worry about kidney problems now, but you may have reason to be wary about the future.
For the purposes of donation, your kidney function is measured by creatinine clearance. This is an easy test to do, but isn’t particularly accurate. Your measurement can change significantly from test to test. There may be significant racial and dietary effects that aren’t considered in the process.
Current kidney function isn’t a fantastic guide to future kidney function. Your kidneys can work at different levels. Their full capacity is a function of their nephron count and it is hugely variable between individuals. If you don’t have a lot of nephrons but they’re working overtime, you might have a high GFR even though your prospects for the future aren’t great. There is no good way to assess your nephron count.
Individual doctors have leeway to reject people who they think are at particular risk, but they have moral and financial incentives to err on the side of accepting borderline acceptable candidates and the formal requirements don’t require exceptional kidney function.
Some nuance here… First, every transplant center has different protocol in how they determine eligibility. There are some general basic requirements nearly all centers follow but beyond that there’s a lot of variability.
Second, NKR leads the world in donor protections. NKR-affiliated transplant centers have better outcomes all around. They tend to do better, more thorough donor screenings. You can evaluate transplant centers here: https://www.kidneytransplantcenters.org/
About GFR, most equations (whether they are creatinine based or cystatin-c) do in fact use age to adjust. And many centers will run both tests, as well as additional tests like a nuclear renal scan to determine kidney function, size, etc. There are no clear ways to determine the future but there are lots of tests that indicate whether someone is a high or low risk for future kidney disease.
Also regarding age, there is a good reason most centers prefer to take kidneys out of middle age people rather than young people: life habits are more strongly established and future health is easier to estimate because many of the most risky activities the person will engage in are in the past.
Regarding the need/idea of “exceptional kidney function.” Most humans living in societies with modern medicine do not need two kidneys; most can live just fine with partial function of one kidney.
You are right to worry about future kidney health, particularly in the age of poor public health and pandemics. For instance, I believe there is a high likelihood that CKD will increase among donors who have caught COVID. And hospital-acquired COVID is not even reliably discussed in the data yet, so making a decision NOW about becoming a living kidney donor is definitely more of a gamble than it was pre-pandemic.
Every transplant center has an evaluation team. It is never just an individual doctor who makes a decision about a candidate. This is good and bad in my opinion, but it speaks to your last point about incentives.
Personally my experience felt like there were a lot of roadblocks to becoming a donor; they don’t make it easy. Someone needs to be pretty motivated to even get to the point where the team makes a decision and by then you have had access to all of your test results so you can consult with other doctors if you wish.
For the record, the screening process is not just looking at kidney health. It’s also looking for cancers, heart health, etc. They are looking for anything that could make your surgery dangerous, anything that could harm your recipient, and anything that suggests longterm negative health consequences for you post-surgery. They have strong incentives to keep their rankings high with good outcomes and I believe those incentives outweigh any incentives you mentioned.
Great post, and I’m a little sad that kidney donation has fallen a bit out of EA discussions. I also want to emphasize two things to people who are worried about the health risks from donating their kidney.
As the OP says, you have to have substantially above average kidney functioning in order to be eligible. I recall seeing estimates that because of this screening, living donors are actually at lower risk for kidney disease than the general US population. But I can’t find them so take that with a grain of salt.
Being a living kidney donor sends you to the top of transplant lists, so in the extremely unlikely event that you do have kidney problems, you are far more likely than average to receive a transplant quickly.
When I looked into this, I came away with the impression that this is not true. According to the formal requirements, you don’t need to have above average kidney function to be eligible. You need to not have a recorded history of kidney disease and take a test that weakly indicates that you are currently in the healthy range.
The healthy range isn’t tied to your age. A young person with healthy kidney function can expect to probably have reduced kidney function in old age. The cut off for donation is a GFR of 90 (though doctors can accept patients as low as 60 in some cases). If your GFR is 90 and you’re 80 years old, you’ve got great kidney function. If your GFR is 90 and you’re 30, you don’t have to worry about kidney problems now, but you may have reason to be wary about the future.
For the purposes of donation, your kidney function is measured by creatinine clearance. This is an easy test to do, but isn’t particularly accurate. Your measurement can change significantly from test to test. There may be significant racial and dietary effects that aren’t considered in the process.
Current kidney function isn’t a fantastic guide to future kidney function. Your kidneys can work at different levels. Their full capacity is a function of their nephron count and it is hugely variable between individuals. If you don’t have a lot of nephrons but they’re working overtime, you might have a high GFR even though your prospects for the future aren’t great. There is no good way to assess your nephron count.
Individual doctors have leeway to reject people who they think are at particular risk, but they have moral and financial incentives to err on the side of accepting borderline acceptable candidates and the formal requirements don’t require exceptional kidney function.
Some nuance here… First, every transplant center has different protocol in how they determine eligibility. There are some general basic requirements nearly all centers follow but beyond that there’s a lot of variability.
Second, NKR leads the world in donor protections. NKR-affiliated transplant centers have better outcomes all around. They tend to do better, more thorough donor screenings. You can evaluate transplant centers here: https://www.kidneytransplantcenters.org/
About GFR, most equations (whether they are creatinine based or cystatin-c) do in fact use age to adjust. And many centers will run both tests, as well as additional tests like a nuclear renal scan to determine kidney function, size, etc. There are no clear ways to determine the future but there are lots of tests that indicate whether someone is a high or low risk for future kidney disease.
Also regarding age, there is a good reason most centers prefer to take kidneys out of middle age people rather than young people: life habits are more strongly established and future health is easier to estimate because many of the most risky activities the person will engage in are in the past.
Regarding the need/idea of “exceptional kidney function.” Most humans living in societies with modern medicine do not need two kidneys; most can live just fine with partial function of one kidney.
You are right to worry about future kidney health, particularly in the age of poor public health and pandemics. For instance, I believe there is a high likelihood that CKD will increase among donors who have caught COVID. And hospital-acquired COVID is not even reliably discussed in the data yet, so making a decision NOW about becoming a living kidney donor is definitely more of a gamble than it was pre-pandemic.
Every transplant center has an evaluation team. It is never just an individual doctor who makes a decision about a candidate. This is good and bad in my opinion, but it speaks to your last point about incentives.
Personally my experience felt like there were a lot of roadblocks to becoming a donor; they don’t make it easy. Someone needs to be pretty motivated to even get to the point where the team makes a decision and by then you have had access to all of your test results so you can consult with other doctors if you wish.
For the record, the screening process is not just looking at kidney health. It’s also looking for cancers, heart health, etc. They are looking for anything that could make your surgery dangerous, anything that could harm your recipient, and anything that suggests longterm negative health consequences for you post-surgery. They have strong incentives to keep their rankings high with good outcomes and I believe those incentives outweigh any incentives you mentioned.