A mother trying to donate a kidney to her 18-month-old son in need of a life-saving transplant has been denied due to potential health risks.

Ashley Barnaby’s son, Zaccari Buell, is in stage 4 renal failure. He’s spent much of his life in hospitals, including a six-month stay at the IWK Health Centre in Halifax.

“The only thing keeping him healthy enough is dialysis,” said Barnaby. “Nobody wants to live on a machine.”

Barnaby says Zaccari is near the top of the transplant list.

“If we get a call that there is a kidney available for him, we can move forward with that. And if that doesn't work out, then it's just a waiting game,” she said.

After a litany of tests, she's been denied the chance to give her son the donation herself. She's healthy right now, but because of her history of high blood pressure and gestational diabetes during pregnancy, doctors say the potential risks are too high.

“I would accept those gladly if it meant that Zaccari would have a normal, healthy life,” said Barnaby.

Had Barnaby been approved as a donor, Zaccari's transplant could have taken place as early as February. Now the family is left waiting.

Marie-Chantal Fortin is a transplant nephrologist at the Universite de Montreal Hospital and a researcher in bioethics. She says transplant teams have to balance the risks and benefits for live donors - both medically and emotionally.

“The objective of the living organ donation team is not to cause harm now or in the future for the potential living organ donor,” said Fortin.

Fortin says there are times when health factors result in the donation being ruled out.

In a statement to CTV News, the medical director of the living kidney donation program said the program follows national and international guidelines when assessing applicants for donation.

“Unfortunately, there are times when health factors result in the donation being ruled out,” wrote Dr. Christine Dipchand. “In these cases, we know that it can be extremely difficult and frustrating for the patient, and as health-care providers we share in that disappointment.”

Barnaby says potential donors should be able to weigh the risks themselves.

“As a donor, as a mom, as an individual, I should have the opportunity to voice my concerns,” she said.

For now, Zaccari's case has been referred to a panel of kidney specialists.

“Hopefully they see my need for it right now because Zaccari is only 18 months old,” Barnaby said.

Barnaby says she just wants to see her son grow up healthy and live a normal life.

With files from CTV Atlantic’s Sarah Ritchie.