Live Kidney Donors Experience GFR Increases
VANCOUVER, British Columbia—A Swedish study has confirmed that people who donate kidneys experience an increase in glomerular filtration rate (GFR) for more than a decade after nephrectomy.
The investigators determined that the average estimated GFR (eGFR) among donors who are 30 years old increases for 17 years then gradually declines. Similarly, 50-year-old donors will experience an increase in eGFR for 15 years followed by an annual drop of 1 mL/min/1.73 m2.
“The latter finding, in particular, is quite remarkable when you consider that the normal progression of renal function in a 50-year-old is an annual decrease of 1 mL/minute/1.73 m2, lead investigator John M. Söfteland, MD, a transplant surgeon at the Sahlgrenska University Hospital in Gothenburg, said after presenting these results at the XIII International Congress of The Transplantation Society. “Our data show that this group does experience this decrease in renal function, but only after they reach 65 years of age.”
Dr. Söfteland's team collected data from 823 kidney donors, 688 of whom answered the investigators' questionnaire and 573 of whom agreed to allow their current renal function to be measured. Among the latter, all 573 had their eGFR determined and 183 had their mGFR determined. They individuals had donated kidneys between 1965 and 2005, and the data collection occurred between 2007 and 2009.
The 573 subjects' mean age at donation was 47 years and their mean time since donation was 14.9 years. At the time Dr. Söfteland's team conducted their study the subjects' mean eGFR was 70.6 mL/min/1.73 m2 and their average measured GFR (mGFR) was 67.9 mL/min/1.73 m2.
The patients' eGFR and mGFR both decreased with age. The team's statistician then performed detailed statistical analyses to arrive at the curves for eGFR and mGFR over time for patients of two arbitrarily chosen ages at donation, 30 and 50 years.
The results indicated that the median eGFR in a 30-year-old donor increases for 17 years following nephrectomy and then remains constant for eight years before slowly declining. Fifty-year-old donors enjoy an eGFR increase for 15 years before the gradual fall begins. Dr. Söfteland pointed out that there were more donors in the study who were closer to 30 years of age at donation than 50, and hence the result for the younger patients may be more robust.
Commenting on the findings, Paul Keown, MD, Director of Immunology at the University of British Columbia in Vancouver, called the research by Dr. Söfteland's group a “nice, large cohort study” that confirms the findings of a larger study published by a group at the University of Minnesota in Minneapolis (N Engl J Med. 2009;360:459-469).
“This is a very good estimate of what we anticipate to happen after kidney donation,” Dr. Keown said. “It has the usual shortcomings of any retrospective observational study, but I think in general it confirms our understanding that donors do well.”