Live Kidney Donors Experience GFR Increases

[Karol]

Live Kidney Donors Experience GFR Increases
Rosemary Frei, MScMarch 14 2011
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.”

http://www.renalandurologynews.com/live-kidney-donors-experience-gfr-increases/article/198285/

[WilliamLFreeman]

Karol & y'all,

An *increase* of GFR after donation is biologically and physiologically improbable if not impossible.  So, I do not know if Renal and Urology News's reporter simply mis-reported what Softeland reported, or Softeland let her/his statistical analysis mis-represent the data.

What may be relevant is that the GFR decreases only slowly if at all until older age, and than starts to decrease at a rate comparable to everyone else's GFR at that age.  THAT finding is physiologically & biologically possible, and is a positive finding worth reporting.

Bottom line:  wait until the article appears in a good peer-reviewed journal -- and then, still, analyze with a scientifically critical eye!   

Bill

[Karol]

Here is the study referenced by Paul Keown, MD, Director of Immunology at the University of British Columbia in Vancouver: "Long-Term Consequences of Kidney Donation" http://www.nejm.org/doi/full/10.1056/NEJMoa0804883

[WilliamLFreeman]

Karol & y'all,

McKeown's statement is just fluff, and is actually unrelated to the report in question.  Softeland did not report the mortality rates or outcomes of the cohort of LKDs studied, except for the outcome of the cohort's average GFR.  I want to know what was the change of each LKD's GFR over time [i.e., how many people increased their own GFR & by how much, how many stayed the same, and how many decreased & by how much], not the averages of the group over time.

The NEJM article shows that LKDs do not die "like flies" after donation.  That indeed is an important finding, and is the best study to its date (and since) indicating that.  But it does *not* show that donation has no adverse effects on the health and longevity of living kidney donors [LKDs] -- because it cannot.  Observational studies simply cannot prove that.  (For example, many observational studies purportedly proved that estrogen hormone replacement decreased women's chance of having a heart attack and of dying from heart attacks -- but the Women's Health Study, a randomized clinical trial, proved those many observational studies to be incorrect.  I can explain why they were incorrect off-LDO.)

After an exhaustive, I mean exhaustive!, study of all the research reports about outcomes of living kidney donation up to early 2008 -- and, as a researcher myself, I know how to read such articles -- I had concluded that LKDs do not "die like flies," so I decided to be a LKD.  But I never once thought that it had been *proven* that donation had no appreciable adverse effect.  I hoped that it had no adverse effect, and took the chance that it may have an adverse effect with my eyes open.    I still have that hope, but know that I/we will not know for sure until the controlled clinical trial of living kidney donation is completed and results report --  2-3 years to go, I think.

Bill