Kidney Function Deteriorates in Overweight Donors

Sandra Yin

May 22, 2012

May 22, 2012 (Washington, DC) – Obese and overweight living kidney donors face a higher risk for long-term renal damage after donating, compared with donors with a normal body mass index (BMI), according to preliminary findings from a systematic meta-analysis of 9 studies presented here at National Kidney Foundation 2012 Spring Clinical Meetings.

The researchers found a decrease in kidney function 1 year after transplantation among living donors with a BMI above 30 kg/m². "With extrapolation, it appears to be maintained up to 10 years postdonation," they conclude.

"Our analysis showed that there is a risk of kidney damage for people who are obese," said Kalyani Murthy, MD, MS, senior staff physician in internal medicine at the Lahey Clinic and associate clinical professor of medicine at Tufts Medical Center in Boston, Massachusetts.

This meta-analysis is one of the first to consolidate disparate findings related to outcomes for obese kidney donors. Transplant centers need to be aware of the risk when counseling possible donors, she added.

It is important to focus on "what these patients who are obese and overweight have as risk factors to begin with when they donate a kidney, and what they could have later," she said.

Although data on overweight individuals are limited, kidney-related outcomes, such as high blood pressure, proteinuria, and the development of chronic kidney disease (CKD), have been reported in overweight donors, Dr. Murthy explained.

Although the pool for potential donors has been expanded to include overweight and obese individuals, current parameters might not be stringent enough, Dr. Murthy said. Obesity (BMI above 30 kg/m²), which is considered a significant risk factor for morbidity and mortality, is also a risk factor for proteinuria and CKD in patients who undergo a unilateral nephrectomy. Studies have demonstrated that higher BMI is an independent risk factor for the development and progression of CKD.

"The relevance of this is really 2-fold," said NKF president Lynda Szczech, MD, SMCE, FNKF, medical director of pharmacovigilance at Pharmaceutical Product Development, a contract research organization that provides expertise in clinical trial development, management, and postapproval services.

"First, it allows us to protect the safety of our donors," Dr. Szczech said. The threshold for donation may need to be lower or reconsidered to protect their safety, she told Medscape Medical News.

Second, she said, we should look at the issue from a more panoramic viewpoint, and use it to understand how best to prevent kidney disease. "If we're seeing kidney damage in people who are otherwise healthy but who have a few extra pounds," she said, "what do those kidneys look like in 20 years?" Perhaps it is possible to prevent kidney disease by addressing issues like diabetes and hypertension, she noted.

It won't be possible to say how much of a decline in kidney function will occur until studies provide data 10 and 20 years down the line, Dr. Murthy told Medscape Medical News. Each study in the meta-analysis was different in terms of how they measured and reported kidney function.

On her wish list for the future are several things that need to change so she and her research team can draw more definitive conclusions: data must be collected in a timely manner; data must be collected in a more uniform way across all BMI categories; and kidney function must be accurately measured before and after donation and at regular intervals.

To protect potential or actual overweight kidney donors, the researchers call for interventions to assist with weight loss and prevent weight gain before and after donation, early recognition and intervention to control hypertension and proteinuria, and steps to prevent further deterioration after spotting significant changes in kidney function and key risk factors.

Dr. Murthy has disclosed no relevant financial relationships. Dr. Szczech is employed by Pharmaceutical Product Development.

National Kidney Foundation (NKF) 2012 Spring Clinical Meetings: Poster 305. Presented May 10, 2012.

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