Extreme Obesity Affects Chances Of Kidney Transplantation

Led by Dr. Dorry L. Segev of the Johns Hopkins University School of Medicine, the researchers used data from the United Network for Organ Sharing (UNOS) to examine how obesity affects waiting times for kidney transplantation.

"The results identify a potential bias in organ allocation that is not consistent with the goals of our allocation system," Dr. Segev comments. "Obese patients are waiting longer for kidney transplants when compared with their non-obese counterparts, even after adjusting for all medical factors tracked through UNOS."

Dr. Segev and colleagues analyzed data on more than 132,000 patients wait-listed for kidney transplants from 1995 to 2004. As obesity increased, the likelihood of receiving a transplant decreased.

Adjusted for other factors, the chances of receiving a kidney transplant were 27 percent lower for patients classified as severely obese and 44 percent lower for morbidly obese patients, compared to normal-weight patients. (The chances of receiving a transplant were not significantly reduced for patients classified as overweight or mildly obese.)

In addition, when a kidney became available, patients in the highest categories of obesity were more likely to be "bypassed"--that is, their physician was more likely to decline the offer of a kidney. The chances of being bypassed were 11 percent higher for severely obese patients and 22 percent higher for morbidly obese patients.

The findings raise concerns that obesity may be a previously unappreciated source of bias in organ allocation. "It is possible that providers are bypassing obese patients and instead transplanting non-obese patients because they feel that kidneys are a scarce resource and they want the kidneys to go to the patients who will benefit most from them," says Dr. Segev. "However, there is strong evidence that even obese patients will benefit significantly from a kidney transplant. And more importantly, the U.S. organ allocation system is not based on such medical decisions, but instead is based on the notion that everyone who gets listed deserves a fair chance at getting transplanted."

The bias might play out in other ways as well. Obese patients tend to have worse outcomes, which may reflect badly on the results achieved by doctors or hospitals--possibly even affecting quality measurements, which are increasingly tied to reimbursement. In addition, the reimbursement for transplant surgery is the same for difficult or complicated cases as for simpler cases. "These two practices generate a strong disincentive against challenging cases, and could potentially contribute to the bias against obese patients that we saw in our study," says Dr. Segev.

Dr. Segev notes that matching an available organ with an appropriate recipient requires clinical judgment, which could not be fully captured in this study. "However," he adds, "it is unlikely that these factors could explain such dramatic observations."

This study is scheduled for publication in the February issue of the Journal of the American Society of Nephrology (JASN) and early online publication.