Increasing numbers of people are on kidney transplant waiting lists. However, the number of potential living donors may shrink as more Americans qualify as pre-diabetic, making them less than ideal donor candidates.
To explore suitability of kidney donors among people who may one day become diabetic, a small study in California sought answers from people who had already donated to see how they are doing 10 years later.
People with prediabetes typically are turned away as kidney donors because of a potential risk of developing diabetes that could ultimately result in kidney failure, said lead researcher Sindhu Chandran, MD, of the University of California, San Francisco, who presented the study during Kidney Week 2012, a conference of the American Society of Nephrology held in San Diego.
Researchers identified 35 people with prediabetes who had donated a kidney between 1996 and 2005. Kidney function had remained well-preserved in all donors and only 11% had developed diabetes within the 10 years since they had donated a kidney.
While the number of kidney transplants with both deceased and living donors has slowly crept up over the last decade, it has not kept pace with the rise in the number of kidney patients on the wait list, Chandran said. “So you see a huge gap in the number of transplants and the number of patients who are on the kidney transplant waiting list.”
There are numerous steps in the process during which potential donors might be ruled out as possible candidates, which can impact the low rate of living kidney transplants, according to Chandran.
“There are a lot more people who volunteer to donate and step forward to donate a kidney to a loved one but only a few of them end up donating,” explained Chandran. One study from South Carolina found that the primary reason was concern about the donor’s health. Furthermore, the risk of developing diabetes or hypertension in the future was the top reason for about 40% of those turned away for medical reasons.
As defined by the American Diabetes Association, anyone with a fasting glucose greater than 125 is considered diabetic. People without diabetes normally have a fasting glucose less than 100, Chandran said.A commonly cited statistic says that the people who are in the middle of normal and diabetic fasting glucose will develop diabetes over the next 3 to 5 years, she said. “One in three U.S adults is prediabetic, and this is often a barrier to kidney donation,” Chandran said.
“We are often turning these people down because we think that they might develop diabetes and potentially kidney failure in the future.”
Transplantation guidelines shy away from making firm recommendations and note that risk should definitely be considered, Chandran said. “So there is no pure consensus when it comes to recommendations from these transplant societies,” she said.
Given the large number of people with prediabetes, Chandran and her research team sought to find out what happens to prediabetic kidney donors in the long run.
Out of 145 donors initially identified in the retrospective single-center study, 35 agreed to participate.Among that final group, the majority was white, 40% were men, about 50% were related to the organ recipient, and 25% had a family history of diabetes.
Researchers conducted telephone questionnaires with participants and ran laboratory tests of their blood and urine to check for kidney function. Checks for abnormal glucose and blood pressure revealed that four out of the 35 donors had developed diabetes since donating a kidney. None of the four was on insulin.
“When we asked about blood pressure, it turns out the 42% of them had developed high blood pressure,” said Chandran, noting that 34% were actually taking medications to control blood pressure.
Lab data showed that fasting glucose measures had improved for 60% of participants 10 years later and that only two had abnormal protein leakage in the urine, which was minor, she said. The data revealed that those who developed diabetes tended to be 8 to 10 years younger than the others in the group with a trend toward younger age and higher fasting plasma glucose. Overall, there were no significant differences in kidney function.
Chandran said the study results are encouraging because they could potentially lead to a safe expansion of living kidney donation. Given that diabetes is the leading cause of kidney failure in the US and around the world, an accurate estimate of risk is necessary to set policy and counsel potential donors, she said.