Any transplant begins with a phone call but on Sunday, the phone in the Cardiff Transplant Unit kept ringing.
It was to prove the start of a remarkable few days as specialists at University Hospital of Wales completed six kidney transplants in 30 hours.
The marathon effort was a test of their professionalism, skill and endurance.
But staff were rewarded with the knowledge that half a dozen people no longer require dialysis thanks to their efforts.
Working in three teams of eight, consultants, anaesthetists and nurses worked around the clock from Monday afternoon until the early hours of Wednesday, stopping only to grab a few hours sleep and a bite to eat before the next life-saving procedures.
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"It's not unusual to have more than one transplant on the go, but we usually don't get anywhere near that number over that period of time," said Dr Mike Stephens, a transplant surgeon for 14 years.
"Offers started coming through to the unit on Sunday evening and then just kept coming through. It was very uncommon.
"Part of being a surgeon is learning how to manage tiredness and know your limits so you ask the next person to take over."
Time is of the essence when it comes to organ donation.
The aim is to complete transplant within 15 hours of retrieval, otherwise the health and function of the organ ticks away with the time.
Then there is the battle for theatre space.
"We always have more than one surgeon on call at any time because it would be a disaster if we had a perfectly good organ but couldn't do the transplant because we didn't have the staff," explained Dr Stephens.
"In Cardiff, we share the two operating theatres with all the other emergency procedures, so that's often a challenge."
Each procedure - to re-attach the kidney to the artery, blood vessels and ureter - takes less than four hours, though surgeons are only too aware of the consequences of a mistake.
"We had two teams in Cardiff and one on the road doing the organ retrieval. It gets complicated trying to join it all up. The operation itself is actually the simple part," Dr Stephens added.
"The challenge is making the judgement on suitability. There's always a risk and putting a kidney in someone that won't work can cause long-term harm and actually make it more difficult for another transplant in the future."
'Best job in the world'
Staff could have been forgiven for enjoying a moment to celebrate their tireless work. However there was no time to toast their efforts as most were back in work the following day.
"It's the best job in the world. I can't imagine there's another profession that's more rewarding than a transplant surgeon," said Dr Stephens.
"We didn't have time to celebrate, but seeing the patients recovering on the ward was reward enough. It was fantastic."
Since 2015, adults in Wales are presumed to have consented to organ donation unless they have opted out, leading to an increase of people on the organ donor register.
"Other areas of the UK are looking at Wales with envious eyes," said Dr Stephens.
"The change of law in Wales has made a difference. We have the highest rates consent in the UK, having previously had the lowest."