Kidney Function Declines in Overweight Donors

Washington, DC (May 10, 2012) - Living donors who are obese or overweight are more likely to sustain long-term kidney damage after donation, according to a systematic review presented at the National Kidney Foundation's 2012 Spring Clinical Meetings.

The research team, led by Kalyani Murthy, MD at Tufts University School of Medicine in Boston, found a marked decrease in kidney function one year, post-transplant for living donors with a Body Mass Index (BMI) over 35.

BMI is an approximation of an individual’s body fat percentage based on their weight and height. Normal BMI usually ranges between 18 and 25, with overweight designated between 25 to 30 BMI, and obese being above 30 BMI. Potential donors with BMI greater than 30 are warned of an increased risk of developing chronic co-morbid conditions if they donate a kidney, while those over 35 BMI are generally rejected from the donor pool.

However, Dr. Murthy’s results also showed evidence of a high incidence of kidney damage to those donors with a BMI of 30 to 35 as well. Studies with long-term follow-up, found that the observed kidney damage in the obese and overweight was sustained for up to ten years.

"Our analysis showed there is a risk of kidney damage for those people who are just overweight and not obese," Dr. Murthy said. "Transplant centers need to be aware of this when counseling potential donors.”

Dr. Murthy’s study is one of the first to consolidate disparate findings pertaining to the outcomes of overweight kidney donors. Using nine previous studies with follow-up times between two months and ten years, Dr. Murthy’s team developed an overall meta-analysis on kidney function in overweight living donors.

Dr. Murthy will be continuing her work, which she believes could help shape criteria on organ donation over time. For now, she feels the results indicate the need to develop uniform testing for GFR in obese kidney donors, and stricter kidney testing post-donation. However, more long-term studies are needed to better characterize the findings.

"This research will have implications for guidelines regarding kidney donation and also how obese and overweight living donors are monitored post-transplant,” said Lynda Szczech, MD, National Kidney Foundation President.

The National Kidney Foundation is dedicated to preventing and treating kidney disease, improving the health and well being of individuals and families affected by these diseases and increasing availability of all organs for transplantation. For more information visit