by George Taniwaki
The 2013 American Transplant Congress was held in Seattle two weeks ago. Two papers were presented that are of interest for kidney donors. Both of them discuss the issue of lower renal function after donation.
Recent kidney donors are experiencing greater declines in eGFR than in past
In the first paper entitled “First-Year Renal Function Changes among Living Kidney Donors (LKD) in the United States”, researchers led by Emily Heaphy at the Cleveland Clinic compared the short-term (one-year) change in renal function of donors. They compared results by race (white/Caucasian, Hispanic, African-American, Asian, and Native American), age, gender, obesity (as measured by body mass index), blood pressure, and by year of donation (from 2004 to 2011).
The findings are that all donors have higher creatinine levels and lower estimated glomerular filtration rate (eGFR) post-surgery. This is not a surprise. They also found differences by demographic characteristics. African-American, Asian, and Native American donors had bigger increases in creatinine than white/Caucasian or Hispanic donors.
Older donors, especially over 50, had greater increases than younger ones. Men had greater increases than women. There were no differences based on BMI or BP. The one-year decline in eGFR has been getting bigger over time. Donors in 2004 had an average 24.9ml/min drop while donors in 2011 had a 29.9ml/min drop.
The study was retrospective and was based on the data from over 31,000 living kidney donors in the Scientific Registry of Transplant Recipients (SRTR). As mentioned in previous blog posts (for example Nov 2009), donors are not tracked, so data beyond one or two years past donation is generally not available. Thus, it is not possible to say what the long-term consequences of low eGFR will be. That is, we don’t know if low eGFR after surgery is an indicator of any adverse health effects in the future. Also, there is no explanation why the decrease in eGFR is greater today than in the past.
The results of this study are of special interest to me, since I am Asian, male, and was 51 years old when I made my donation in 2010.
Low eGFR after donation does not lead to kidney disease
On the positive side, a second paper entitled “Low GFR after Kidney Donation Is Not Chronic Kidney Disease” provides evidence to an idea I posited in an Apr 2011 blog post.
The abstract of the study says, “Many kidney donors have an estimated GFR<60 mL/min/1.73m early post-donation and thus meet with criteria of chronic kidney disease stage 3 (CKD3). However, the prognosis of a low GFR with one healthy kidney may not be equivalent to the prognosis of the same GFR with two diseased kidneys.”
A study led by Laura de Vries and colleagues at University Medical Center Groningen in the Netherlands followed two groups, patients with early stage CKD and recent donors, for an average of 4.7 years. At the start of the study the CKD patients had an average GFR of 67 ml/min compared to 71 for the donors. By the end of the study, the patients’ average GFR had fallen to 63ml/min (slope of –1-4ml/min/yr) while the donors had risen to 73 (slope of +1.8).
The results are based on a small prospective study of 57 post-donation kidney donors and 57 CKD patients who were matched for age, gender, GFR, and time of follow-up. GFR was measured rather than estimated, using 125I-iothalamate tracer rather than creatinine. Kidney function slope was calculated as (GFR follow-up – baseline GFR)/duration of follow-up, giving a slope in ml/min/year.
Change in GFR for patients and donors over four years