Medics have used 3D printing to help surgical teams performing a kidney transplant from a father to his daughter.
Experts at Guy's and St Thomas' NHS Foundation Trust said that it is the first time the technique has been used to support the successful transplantation of an adult kidney into a child.
After suffering heart failure as a baby, Lucy Boucher's kidneys began to shut down.
Lucy, now aged two, faced a lifetime on dialysis due to her kidney failure until surgeons performed transplant surgery with a kidney donated by her father Chris, 35.
Models of Mr Boucher's kidney and Lucy's abdomen were produced using a 3D printer so that the surgeons from Guy's and St Thomas' and Great Ormond Street Hospital could accurately plan and rehearse the operation.
The Bouchers, from Antrim in Northern Ireland, had the surgery in November and are both recovering well, a Guy's and St Thomas' NHS Foundation Trust spokesman said.
When Lucy was a baby she developed supraventricular tachycardia - an irregularly fast heartbeat - which resulted in her body, including her kidneys, being starved of oxygen.
After surgery to correct her heart problem, the youngster needed a new kidney - which was provided by her father, an assistant lay minister.
Mr Boucher said: "My first reaction when I saw the 3D printout of my kidney was surprise at how big it was and I wondered how it could possibly fit into Lucy.
"Seeing the model of her abdomen and the way the kidney was going to be transplanted inside her gave me a clear understanding of exactly what was going to happen. It helped ease my concerns and it was hugely reassuring to know that the surgeons could carry out such detailed planning ahead of the operation."
Lucy's mother Ciara, a teacher, added: "We found it amazing that we could see these incredibly detailed models of Chris' kidney and Lucy's abdomen.
"Considering all the potential complications, it's fantastic that everything has gone so well - it's a massive relief. The transplant is life-changing for Lucy."
Mr Pankaj Chandak, a transplant registrar at Guy's and St Thomas' whose idea it was to use 3D printouts, said: "Our exciting new use of 3D printed models to help plan highly complex kidney transplant surgery in children brings all sorts of important advantages for our patients and the surgical team.
"The most important benefit is to patient safety. The 3D printed models allow informative, hands-on planning, ahead of the surgery with replicas that are the next best thing to the actual organs themselves.
"This means surgeons are better placed than before to prepare for the operation and to assess what surgical approach will offer the greatest chance of a safe and successful transplant."