Kidney donors' survival rate same as non-donors'

April 1, 2009

For the first time, clinicians have solid evidence from a large, long-term study that kidney donors have survival rates similar to those of the general population, and that donors are at no higher risk for developing end-stage renal disease, hypertension, diabetes, and cancer than non-donors are.

Minneapolis-For the first time, clinicians have solid evidence from a large, long-term study that kidney donors have survival rates similar to those of the general population, and that donors are at no higher risk for developing end-stage renal disease, hypertension, diabetes, and cancer than non-donors are.

Those are the conclusions reported by University of Minnesota investigators, who examined the records of 3,698 individuals who donated kidneys between 1963 and 2007.

The Minnesota team randomly selected 255 of the donors for closer evaluation, including measurement of glomerular filtration rate (GFR) and urinary albumin excretion, and assessment of the prevalence of hypertension, general health status, and quality of life.

Moreover, end-stage renal disease developed in only 11 donors. That's a rate of 180 cases per million persons per year, well below the 268 per million persons per year rate seen in the general population.

Results of the study were published in the New England Journal of Medicine (2009; 360:459-69).

"These results are almost consistent with what people have expected," said lead author Hassan N. Ibrahim, MD, associate professor of medicine and director of the renal fellowship program at the University of Minnesota. "We had always suspected that donors are healthy to begin with and should do better than the general population."

Data culled from the 255 donors who underwent more thorough examination were especially valuable, Dr. Ibrahim said. At a mean of 12.2±9.2 years after donation, 85.5% of that subgroup had a GFR of 60 mL/minute per 1.73 m2 of body surface area or higher, while 32.1% had hypertension and 12.7% had albuminuria.

Factors associated with lower GFR and hypertension included older age and high body mass index, but not length of time since donation, although longer time since donation was independently associated with albuminuria.

Most donors had quality of life scores superior to population norms, while the prevalence of coexisting conditions was similar to that of controls from the National Health and Nutrition Examination Survey who were matched for age, sex, race/ethnic group, and body mass index.

"This is really sort of a philosophical debate," said Dr. Ibrahim. "If a 25-year-old person wants to donate a kidney to his brother, for example, you make sure he has no hypertension or diabetes and isn't overweight. They're healthy on the day you evaluate them, but are they still healthy afterward? Even years later?"

Data useful, with one flaw

While acknowledging the significance of his group's work, Dr. Ibrahim also noted at least one flaw: the lack of a truly appropriate control group.

"What you want [in a control group] is someone who has passed the same health screenings that donors underwent and compare them in terms of survival and outcomes," he said. "But that's impossible. How would you find someone like that from 30 years ago? So I do think that puts this study in perspective.

"Still, it does appear that if you screen donors carefully, they seem to live as long if not longer than the general population. My hope is that this will encourage people to at least pursue kidney donation and that at least some of their fears or concerns will be alleviated."

Results of the study were published in the Jan. 29 issue of the New England Journal of Medicine (2009; 360:459-69).

In an accompanying editorial, authors Jane C. Tan, MD, PhD, and Glenn M. Chertow, MD, cautioned against "extrapolating the data from the study of Ibrahim et al to older donors, who are often spouses or loved ones of affected patients." Average age at the time of donation in the Minnesota study was 41 years, and Drs. Tan and Chertow noted that nephron mass and kidney function decline steadily with age, especially after the sixth decade.