'My friend made a promise I hoped I'd never need. Years later, I found out if she meant it.'

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When Gaynor was 33, she returned home from a Christmas shopping trip to discover her legs had swollen dramatically.

It didn't feel urgent, but it didn't feel right either.

Gaynor's GP sent her to a renal specialist and within weeks she received the diagnosis that would shadow the rest of her life: kidney disease. The news marked the beginning of what would become an ongoing battle against chronic kidney disease.

"We tried to manage it through various treatments," Gaynor told Mamamia. "I underwent a couple of courses of light-dose chemotherapy to slow down the change in the cells and try to prolong the progression of the disease.

"But the end result was always going to be the need for a kidney transplant."

A friendship that Gaynor had struck up decades earlier at her husband's Christmas party would become one of the most defining threads of her life.

Gaynor (left) and Christine (right) have been friends for decades. Image: Supplied.

"Christine and I hit it off straightaway," Gaynor said.

"We liked each other, we lived close to each other and had similar ages and interests."

By 45, Gaynor's disease tipped into end-stage kidney failure. Dialysis loomed. Fear set in — practical, not panicked, but unmistakably urgent. She picked up the phone and called Christine.

"We were such good friends and we'd known each other for 20 years by then," Gaynor explained.

"Christine had said from the beginning, 'My kidneys are great, I'll give you one.' But you get offers like that and you think, 'did they really mean it?'"

So Gaynor asked the simple question.

Christine didn't hesitate.

"She absolutely did," Gaynor said.

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'It's a no-brainer.'

For Christine, the decision wasn't framed as a once-in-a-lifetime moral test. It was strangely straightforward.

"You know, her not getting a kidney would have huge life consequences for her and for her family," she told Mamamia.

"It's a bit of a no-brainer.

"There were several people who had let her know that they would be willing to donate a kidney. I was just one of those."

By the time Gaynor made the call, Christine had known for years that her friend's kidneys were deteriorating. She knew about the earlier treatments, the risks and the looming transplant.

But the moment everything crystallised was the night Gaynor was admitted to hospital and told she was entering renal failure.

"She called and said, 'You know how you offered to give me a kidney? Were you serious? Because I'm actually starting dialysis.' And that was that."

It's easy from the outside to imagine nerves, hesitation or a sense of burden, but Christine felt none of it.

There were many tests, confirming she had two kidneys of similar size and strong function. There were psychological assessments ensuring she wasn't acting out of pressure or obligation. Her own renal specialist was assigned to protect her interests alone. There were compatibility tests.

The tests Christine went through were extensive and thorough. Image: Supplied.

"We were actually compatible on three out of six markers," Gaynor said. "For not being related, that was pretty good."

When the final clearance came, neither woman was surprised.

"Weirdly, I wasn't," Christine said. "You just wait and see what the results say, but I felt like we'd be a match."

The surgery took place in Sydney, and it gave Gaynor a sudden surge of health.

"I felt fabulous, like I had a new lease on life," she said, explaining that recovery was harder for Christine.

"Her body lost something, so her body had to compensate and go through its own recovery process.

"Mine gained something."

Within weeks, Christine was also walking, then running. Before long, she was completing marathons.

"It hasn't changed my life at all," Christine said, likening the surgery to a cesarean.

The silent question: What do we owe a donor?

The act of receiving a living organ can raise delicate, unspoken questions: What level of responsibility do I now owe? Must I live differently to honour this gift?

But the strength of Christine and Gaynor's friendship was such that these questions never reared their head.

"We both love each other to bits. We are both very independent, strong women," Gaynor explained.

"She thought of it as a gift. I don't think it's influenced to any degree how my life has gone.

"I don't think that expectation is on me that I should be, you know, a pinnacle of healthy living or a role model for healthy living."

Christine agrees.

"Once you give the gift, that's it," she said. "It's not something you hold over someone."

The kidney Christine gave Gaynor is, in Gaynor's words, "the healthiest kidney ever."

"Beforehand, I was being told my life expectancy was 20 years," Gaynor said. "Here we are coming up for 18 years post-transplant, still on the same kidney.

"It's been a very, very solid kidney."

But the journey is far from over.

Gaynor still sees her renal specialist every three months, takes a complex mix of anti-rejection medications and tracks her blood pressure closely. Years on immune-suppressing drugs have left her with other health challenges.

"There's no clean bill of health," she said matter-of-factly. "It's always something I have to be very careful with.

"I have to look after myself."

Yet she refuses to live in fear, or, with total restriction.

"You sort of have to take a step back and look at what you're doing; how you eat, how you exercise, if you drink, how much you drink," she said.

"I'm not going to be a teetotaller because I have kidney disease.

"You have to enjoy your life and enjoy the time you've got."

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Christine, meanwhile, feels only gratitude that she could help.

"I kind of liken it to any gift," she said. "Once you give that gift, it's not your kidney anymore. It's their kidney.

"If you gave someone a car, you wouldn't tell them how to drive it.

"You wouldn't want that expectation hanging over someone, or, having them feel that they're indebted."

The advice they want others to hear.

Both women know someone right now who is facing the same decision of having a potential live donor.

Gaynor said it's been "fascinating" watching things unfold from the sidelines as has some advice for those navigating the choice.

"Don't shy away from the conversation," Gaynor said. "If someone offers you a kidney, don't think it's a throwaway line. Christine meant it because when it came down to the crunch, there was no thinking twice about it."

Christine and Gaynor have shared their advice to others facing the same choice: Image: Supplied.

And for prospective donors?

"Go into it with your eyes open," Christine said. "Do the tests and find out if you're compatible and then make a decision. It's not an immediate decision that you need to make.

"But it makes such a difference to the person who needs that organ."

As for what she owes Christine, Gaynor doesn't measure it in lifestyle changes or moral obligations. She measures it in something quieter, steadier, lived over decades: friendship.

"I think people come into your life for a reason," she said. "If that was Christine's reason, then that's fantastic. But our friendship would have been the same either way."

Take one minute today to register as an organ donor. It's fast, it's free, and it could save multiple lives. Visit DonateLife and make your decision count.

For more information on living organ donation, click here.

Feature image: Supplied.