Ted Lombard gave his daughter, Denice, one of his kidneys a half-century ago. Now, they are the longest living kidney donor-recipient pair in the world.

The number 50 is a big milestone for most people.

There’s 50th birthday, 50th anniversary, and so on.

When you reach that momentous number, whatever the circumstance, you have plenty of reasons to celebrate.

For Denice Lombard and her father, Ted, celebrating 50 years of a successful kidney transplant is a landmark they never thought they would see.

In August, the Lombards, now the oldest living kidney donor-recipient pair, will celebrate 50 years of healthy living.

In 1967, when the two underwent the transplant surgery in California, they weren’t sure they’d be promised much more than a handful of years.

“Back in the day that she got the kidney transplant, only half of the kidneys survived for more than one year, so it was considered very risky at the time,” Dr. H. Albin Gritsch, surgical director of the kidney transplant program at the University of California Los Angeles (UCLA) Medical Center, told Healthline.

Gritsch was not involved in the Lombards’ care at the time of the surgery, but he still marvels at the progress made the past half-century.

“Today, there are thousands of people on dialysis, and many thousands of people get kidney transplants, so it’s not that unique anymore, but it is still a life-saving procedure for many people,” Gritsch said.

Read more: Kidney donations should be accepted from older donors »

At age 7, Denice’s identical twin, Diane, died from kidney failure.

Like Diane, Denice had a rare genetic disorder that was slowly deteriorating her kidneys. It wasn’t until 2005 that the disorder was diagnosed as Frasier syndrome.

Within a handful of years after Diane’s death, Denice was facing a similar fate if she couldn’t find a cure or a new kidney.

“In those days, kidney transplants were very experimental, and dialysis was not available to most people. They were reserving it for male head of households whose family depended on them,” Denice, who will turn 63 next month, told Healthline.

Undeterred, her parents pressed harder for answers from doctors.

“Especially my mother was extremely intent on finding a solution to keep me alive,” Denice said. “It was fairly quirky that a doctor agreed to do a transplant on me. A pediatrician we had told my mother if she would promise to stop raising hell with all the doctors and hospitals and insurance companies, he would introduce her to this surgeon who was visiting UCLA from Minnesota. To his surprise, he agreed to do it.”

Her father Ted was tested and he was a good match.

“He wasn’t perfect, but it was obviously good enough,” Denice said.

The operation, while not the first of its kind, was certainly not mainstream.

“Fifty years ago, there were a handful of programs in the United States that did kidney transplant, and it was considered experimental,” Gritsch said.

But for Ted, the choice to share his kidney with his surviving daughter was easy. “I lost one daughter,” he said during a press conference at UCLA. “I didn’t want to lose another.”

On August 30, 1967, the two Lombards went under the knife.

Denise needed to stay in the hospital for 21 days to recover and be monitored for complications with the new organ. Her abdomen bears the long scar of a transplant surgery. But today, she’s healthy and active.

“I’ve led a very normal life. I’ve been very, very active. I’ve been politically active. I’ve worked,” Denice said. “I’ve been in a relationship for 35 years. I’ve traveled the world. We’ve hiked hundreds of miles and kayaked and bicycled. I’m healthier than my friends. In fact, I had a knee replacement last year. I’ve lived a long enough life that I’ve used my knee up and had to get a new one, so that was pretty cool.”

Ted, now 88, is also healthy — and he has been thriving, too.

“My dad and I have gone, with our partners, on various vacations together — cross country skiing, kayaking in the inland passage of Canada. So it’s been active and full and normal.”

Read more: Scientists report breakthrough in growing kidneys from stem cells »

Denice’s donor shared a roof with her, but today donors and recipients can be matched even if they’re separated by thousands of miles.

That’s why, on the 50th anniversary of their successful transplant, the Lombards are encouraging others to consider organ donation as a way to save someone else’s life.

Today, donating a kidney isn’t the invasive procedure it was when Ted made the choice to give his second kidney to Denice.

“For a living donor, we can now remove the kidney laparoscopically. That means we make a very small incision and people recover much more quickly than they did back then when her dad donated a kidney,” Gritsch said.

Each day, more than 119,000 people are on the organ donation list. More than 80 percent of those people are waiting for a kidney.

As people are made more aware of how healthy a donor can be after a transplant, more people are choosing to share one of their kidneys. In fact, in 2015, doctors performed more than 17,000 successful kidney transplants.

“We have way more than we need in terms of kidney power,” Denice says. “We can live on part of a kidney, and we have two kidneys.”

If you’re considering donating organs, Gritsch encourages you to first talk with your family about your choice and then put it in writing. You can do this by listing yourself as an organ donor on your driver’s license or recording it in a living will.

Carry a copy of this will or a note expressing your wishes in your personal belongings always. That way, your wishes can be honored at the time of your death.

You can also sign up at OrganDonor.gov. You can register with your state to be a donor, and you can learn more about how to be a living donor.

“So many lives can be saved, so many lives can be helped, that it’s really a wonderful thing to be able to give back in life, and it’s so easy,” Denice said. “We’re all looking for meaning. We’re all looking for purpose and for ways to contribute to the world, and this is one that people shouldn’t miss.”