TORONTO—Living kidney donation has no serious adverse effects on donor kidney function up to four to five decades after donation, and the prevalence of hypertension at that time probably is similar to that in the general population given the donors' age. This was the conclusion of a study with the longest follow-up of living kidney donors to date, presented here at the American Transplant Congress.
“As living kidney donation continues to account for 50 percent of all kidney transplants, I think we owe it to kidney donors to know what the long-term consequences are,” said lead author Hassan N. Ibrahim, MD, Associate Professor of Medicine and Director of the Renal Fellowship Program at the University of Minnesota, in a phone interview.
“I think that one of the two areas that have really lacked in this field is that most of the data on long-term outcomes of kidney donors in terms of how long they survive and whether it's different than the general population has come from Scandinavian countries. There hasn't been a single US study that's actually looked at this. The second major piece is what is the risk of donors going on to develop kidney failure themselves.”
In the study, 302 donors who had donated a kidney at the University of Minnesota more than 35 years earlier were asked to complete a survey about their post-donation medical history and get a physical exam and laboratory testing from their local physician. The current age of the donors was 62.1±11.6, and age at donation was 34.3±10.9.
In terms of vital status, 64% of the donors were alive and 34% had died, while the status of 2% was unknown. Of those who had died, the cause of death was unknown in 60%. Age at death was 73.2±12.7, and time from donation to death was 27.8±8.8 years.
Regarding kidney function, the serum creatinine level 20 years after donation was 1.20±1.30 mg/dL, and the level 34 to 42 years after donation was 1.16±0.52 mg/dL.
Of the whole group, 107 patients were taking antihypertensive medication and 15 had dipstick-positive proteinuria documented.
Outcomes from 3,698 donors who had three to 45 years of follow-up also were presented and compared with data for the general US population.
“We showed data that the survival of these kidney donors is comparable to somebody who's their age, gender, and ethnicity, which is something that's never been done in the US, so I think that's really the major big news in the work,” Dr. Ibrahim said.
Of the 3,698 donors, 11 had received dialysis or a kidney transplant, he added.
“When you compare that risk with the US population it turns out to be 180 per million per year in contrast to 268 per million per year in the US population, so they clearly have a lower risk of developing end-stage kidney failure, which is not surprising given the fact that they're very well screened for hypertension and diabetes— the two most common causes of kidney disease.”
In terms of glomerular filtration rate (GFR), 85% of the donors had a GFR higher than 60 mL/min/1.73 m2, and none had a GFR lower than 30 mL/min/1.73 m2.
Kidney donation also had positive effects on quality of life, Dr. Ibrahim noted.
“Generally 60% of kidney donors regardless of their age had quality of life in the physical and mental domains that is better than the general population.
“Most interesting we looked at quality of life from time from donation to make sure that they're not feeling great from the time of donation because of how healthy they are and whether they're losing ground postdonation, and interestingly the longer they are postdonation the better their quality of life is.”
Need for Confirmation
The strengths of the study are the long length of follow-up, the inclusion of a large number of donors, the use of the Social Security Death Master File to ascertain vital status, and the measurement of the actual, as opposed to the estimated, kidney function of 255 donors at the University of Minnesota, Dr. Ibrahim said.
The biggest limitation, on the other hand, is that 97% of the donors were white, potentially limiting the generalizability of the results, Dr. Ibrahim noted.
These findings need to be confirmed, he added. “These are single-center data, and they need to be confirmed in a larger cohort. The NIH [National Institutes of Health] currently has a study that has three centers in it—the University of Minnesota, the Mayo Clinic, and the University of Alabama.
“Between the three centers we think we have 9,000 donors, and for the last year we have begun an effort to try to put forward a set of studies to literally replicate the University of Minnesota experience to see if donors actually live as long, or if they actually have the risk of ESRD [end-stage renal disease].”
The characteristics of the donors included in this study may differ from those who have donated more recently, Dr. Ibrahim said.
“I think the major message in my mind is that most of these donations were done when there was no leniency about kidney donor criteria. You could not have high blood pressure; you couldn't have any degree of glucose intolerance; you couldn't be overweight.
“I think those strict criteria are paying off because people are doing well. I think there's been a tendency in the last five years to loosen up that strictness, and I'm afraid that may not translate into long-term results like the ones we've shown.”
Donor selection is an issue facing the transplant community as individuals interested in being living donors present with different medical conditions, said Ginny L. Bumgardner, MD, PhD, one of the moderators of the session during which the study was presented, in a phone interview.
The study results reflect the excellent outcomes that can be achieved with good donor selection, added Dr. Bumgardner, who is Professor of Surgery and Associate Dean for Research Education and Graduate Studies at Ohio State University.
‘Unique Body of Work’
While it's unfortunate that the information on causes of death was limited in the study, with the cause of death unknown in 60% of the deceased donors who had more than 35 years of follow-up, the work is very important and offers helpful information to provide to patients for informed consent, Dr. Bumgardner said.
“It's a unique body of work. There are few studies that could provide such experience.”
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