'I was shocked to find out I now have four kidneys'
Stuart Middleton has undergone two operations to receive new kidneys from donors.
But the 46-year-old was shocked when he woke up after the second procedure and was told that all four kidneys were still inside his body.
The father-of-two had assumed that the failed organs would be removed - but says he is just happy to be alive.
"I was shocked and surprised when I found out, I had no idea they had left the old kidneys inside me too," he said.
"Load me up with kidneys, as I want to live longer."
Kidney Research UK said it was normal practice to leave redundant kidneys inside transplant patients.
Stuart, who lives in Lauder in the Scottish Borders, now wears a special belt when he is snowboarding to protect his organs.
He had suffered migraines and stomach pain for a decade before he discovered he had Berger's disease - where a build up of antibodies destroys the kidney's function - in 2007.
Stuart was living in East Lothian at the time and commuting with his wife Mhairi to their workplace in Edinburgh.
Mhairi would drive because he kept falling asleep, but they did not suspect he had anything seriously wrong with him until a colleague suggested he go for blood tests.
The energy trader said: "The hospital said I had 9% kidney function and they didn't know how I was still able to walk."
His mother, Val Middleton, 76, donated him one of her kidneys six months later.
'She saved my life'
"All I could think about was would my body reject her kidney and she would have gone through all this for nothing. The guilt was incredible," said Stuart.
The operation in 2008 was a success and her kidney lasted for nine years.
"I actually felt physically bonded to my mum after the operation. Her kidney was inside me and it forged a very strong bond between us. She saved my life."
A regular biopsy on the donated kidney showed it was in decline after seven years and he became ill again a year later.
Stuart was talking to a colleague, 36-year-old Ninon Ferguson, who worked in his wife's department - and she said she would give him a kidney.
He said: "I didn't think she was serious until the next day she followed up our conversation and said she wanted to do it.
"I was blown away by her altruism. She had a young son at the time. I told her of the side effects but she still said she wanted to do it."
Ninon gave her kidney in November 2017.
He said: "I don't understand it, she didn't have to give me a kidney. She's an incredible woman and I would do anything for her now."
He said he also suffered from feelings of guilt in case Ninon's kidney was rejected.
"The guilt has been replaced by a strong bond now I know it worked," he said.
Stuart said his three older kidneys would now have "shrivelled up like a peanut".
Kidneys are found in the core of the body, but his donor organs are just under the skin so need to be protected carefully.
"I'm not allowed to play rugby and I have a special belt to protect them for other sports," he added.
Professor Lorna Marson, Kidney Research UK spokeswoman and transplant surgeon, said redundant kidneys were left in the body because there is no need to remove them and it is a big operation which should only be carried out if necessary.
She said: "It is actually quite common for transplant patients to have four kidneys. Transplants don't last forever, so people often need more than one.
"The original kidneys would only be removed if they were causing problems, such as repeated infections, or if a patient has multiple cysts on their kidneys and they become very large, leaving no room for the transplanted kidney to go in."
She said four was usually the maximum number of kidneys that a patient would have after multiple transplants.
"Once this is reached, one of the transplanted kidneys is taken out," added Prof Marson.