Becoming a living kidney donor can be a heroic act, but it has its downsides: increased risks of health complications and occasionally, diseases that may create the need for the donor to have a kidney transplant later in life.

In recognition of these possible consequences, living kidney donors who are in need of a transplant have, since 1996, been given priority status to shorten their time on the waiting list.

But according to a study published Sept. 2 in the Clinical Journal of the American Society of Nephrology, prior living donors do not always receive that priority status in a timely manner. Some had to wait for years and go through dialysis before moving to the front of the line — while some possibly never got to priority status.

“This is a big deal to donors and the transplant community,” said Jennifer Wainright, an analyst at the United Network for Organ Sharing research department and the study’s lead author. “Living kidney donors should know that they are entitled to priority if they ever need a kidney, and also that most prior living donors receive their transplant quickly.”

Wainright stumbled upon this issue when she was examining data on donors, waitlist candidates and transplant recipients from the national Organ Procurement and Transplantation Network for another project.

“We put the original project on hold, explored the data, and figured out a way for UNOS to help transplant programs try to prevent the problem in the future,” she said.

The researchers sought to characterize how quickly prior living donors were added to and activated on the transplant list. They studied data related to living donors and their transplant needs from January 2010 through July 2015. During that period, 210 transplant candidates who were prior living donors with priority status were added to the transplant waiting list. As of Sept. 4, 2015, 167 of them received deceased donor transplants, six received living donor transplants, two died, five were too sick for transplants and 29 were still waiting.

Because of the “priority” designation, most of these patients were able to receive transplants quickly, the study found. But a number waited a long time.

For example, among the living donors studied, only 40.7 percent were added to the transplant waiting list before they needed dialysis, which is a treatment that becomes necessary when the kidneys are no longer functioning optimally. Half of the patients in the study were on dialysis for 332 days or longer before their priority was recognized.

The process of requesting the priority status goes like this: If a prior living donor needs a kidney transplant, the transplant program at the hospital will submit information and contact the UNOS Organ Center to request priority. The center is supposed to complete the request within a day. Patients healthy enough to receive the transplant immediately will be listed in an active status.

The reasons for the delays in this process detected by the study may be, in part, due to a patient’s ill health or to paperwork and bureaucratic problems. These can include incomplete data submission and insurance issues.